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Heading here - papers.xtremepapers.com v0.7 3Y06 Cambridge O Level Physics (5054) 1 Contents Overview ........................................................................................................................................................................................................................................ 3 Unit 1: Matter and measurement .................................................................................................................................................................................................... 7 Unit 2: Waves and their uses ....................................................................................................................................................................................................... 15 Unit 3: Atoms and radioactivity .................................................................................................................................................................................................... 28 Unit 4: Moving charges ................................................................................................................................................................................................................ 37 Unit 5: Energy and energy sources .............................................................................................................................................................................................. 48 Unit 6: Thermal energy and matter ............................................................................................................................................................................................... 53 Unit 7: Magnetism and electric current ........................................................................................................................................................................................ 62 Unit 8: Forces and motion............................................................................................................................................................................................................ 72 Unit 9: Pressure and gases .......................................................................................................................................................................................................... 78 Unit 10: Practical electricity ......................................................................................................................................................................................................... 84 v0.7 3Y06 Cambridge O Level Physics (5054) 2 Overview Recommended prior knowledge Since this syllabus involves a consideration of its topics very largely from first principles, very little prior knowledge is required. The course has been divided into ten units, with each unit having a common thread and following the sequence presented in the syllabus. The order of topics as presented is not necessarily the ideal teaching order as teachers might well wish to include examples of most topics in each year taught. Consequently, teachers may wish to alter the order given. Within a unit, however, the order specified makes a great deal of sense and it is clear that the two electrical units should be approached in the order in which they occur. Outline Whole class (W), group work (G) and individual activities (I) are indicated throughout this scheme of work. The activities in the scheme of work are only suggestions and there are many other useful activities to be found in the materials referred to in the learning resource list. Opportunities for differentiation are indicated as basic and challenging; there is the potential for differentiation by resource, length, grouping, expected level of outcome, and degree of support by teacher, throughout the scheme of work. Timings for activities and feedback are left to the judgment of the teacher, according to the level of the learners and size of the class. Length of time allocated to a task is another possible area for differentiation The units within this scheme of work are: 1def Measurement 8% 4abcdefghi Mass, volume and gravity Matter and measurement 2ab Speed and velocity Unit 1 6abcd Elasticity 5abcdef Moments 13abcdef Wave properties 13% Unit 2 Waves and their uses 16abcdefghijk Sound waves 14abcdefghijklmnopq Reflection and refraction 15abcde Electromagnetic waves v0.7 3Y06 Cambridge O Level Physics (5054) 3 Unit 3 27abcdefg Atomic structure 7% Atoms and radioactivity 26abcdfghijklmn Radioactivity 18abcdefghijk Electrostatics 13% Unit 4 Moving charges 19abcdefghijklmnopqr Current electricity 20abcde D.C circuits Unit 5 Energy and energy sources 8abcdefghijklmn Energy 9% 9abcdefg Thermal energy 9% Unit 6 Thermal energy and matter 10abcd Temperature 11abcdefghijklm Thermal properties 17abcdefghijk Magnetism 11% Unit 7 Magnetism and electric current 22abcdef Motor effect 23abcdefgh Electromagnetic induction 1abc Vectors and scalars 10% Unit 8 Forces and motion 2cdefghi Graphs and motion 3abcdefgh Newton?s laws Unit 9 Pressure and gases 7abcdefghi Pressure 10% 12abcdefg Matter and molecules V0.7 3Y06 Cambridge O Level Physics (5054) 4 21abcdefghi Using electricity 10% Unit 10 24abcdefghijklm Electronics Practical electricity 25abcdefg Electronic systems Teaching order The units may be taught in order, 1 to 10. This is not essential, but the following recommendations apply. (a) It is recommended that Unit 1 is taught as the first unit of the course. (b) Other units that are suitable for teaching early in the course include Units 4, 5 and 8. Whenever a new unit is taught, it is essential to revise those ideas which were encountered earlier in the course and are required in the new unit. (c) Some units contain the more conceptually difficult ideas and so are suitable for teaching in the second half of the course; it would be unwise to leave these until the very end, however, when revision is beginning to be a significant factor and when time might be short. These include Units 7 and 2. It is essential, however, that Unit 5 is taught before Unit 6, Unit 8 before Unit 9 and Unit 4 before Unit 10. (d) It is recommended that the teaching of some skills and concepts are ongoing across all units. These include the use of symbols, formulae, equations, calculations, practical skills, molecular theory and ideas about energy. Teacher support Teacher Support is a secure online resource bank and community forum for Cambridge teachers. Go to for access to specimen and past question papers, mark schemes and other resources. We also offer online and face-to-face training; details of forthcoming training opportunities are posted online. An editable version of this scheme of work is available on Teacher Support. Go to . The scheme of work is in Word doc format and will open in most word processors in most operating systems. If your word processor or operating system cannot open it, you can download Open Office for free at www.openoffice.org V0.7 3Y06 Cambridge O Level Physics (5054) 5 Resources An up-to-date resource list for this syllabus can be found at www.cie.org.uk Textbooks: The textbooks used will depend on what is available and what the teacher prefers but since the ideas of physics are the same no matter which course or textbook is used; any O Level, GCSE or IGCSE textbook will deal with the topics at approximately the right level. The content of a particular textbook, however, is unlikely to correspond exactly with the O Level syllabus. Endorsed textbooks: At the time of writing the textbooks endorsed by Cambridge International Examinations for use with the Cambridge O Level Physics syllabus (syllabus code 5054) are: Pople, S Fundamental Physics for Cambridge O Level Oxford University Press, 2012 ISBN: 9780199128181 Sang, D and Jones, G Cambridge O Level Physics (including CD-ROM) Cambridge University Press, 2012 ISBN: 9781107607835 Websites: The suggested learning resources listed in the units in this scheme of work are intended to provide support for learners and teachers following the course. Some resources directly support the suggested teaching activities whilst others provide more general reference, background and extension material. All resources have been checked to ensure their relevance and academic level is suitable for the Cambridge O Level syllabus. All references are to specific web pages rather than to the general site URL and may be followed directly from the electronic scheme or work or typed directly into the address bar of any web browser. A number of animation and video resources rely on the correct plug-in software being installed on the user?s computer (e.g. QuickTime and Flash) – all of which are freely available for download via the internet. This scheme of work includes website links providing direct access to internet resources. Cambridge International Examinations is not responsible for the accuracy or content of information contained in these sites. The inclusion of a link to an external website should not be understood to be an endorsement of that website or the site?s owners (or their products/services). The particular website pages in the learning resource column were selected when the scheme of work was produced. Other aspects of the sites were not checked and only the particular resources are recommended. V0.7 3Y06 Cambridge O Level Physics (5054) 6 Unit 1: Matter and measurement Recommended prior knowledge Little prior knowledge is required here, although learners will need to have encountered the idea of a graph and how, in physics, it is used to represent quantities and the relationships between them. Most of the other ideas are of the sort that many learners will be familiar with at some elementary level, although precise definitions may well be encountered here for the first time. Context This unit introduces learners to the ideas of measurement and observation which are so fundamental to all aspects of physics. From the very beginning, learners should be encouraged to be guided in their understanding of the subject by what has been measured and observed. Physics is not a question of opinion or education. Outline In this unit learners should learn to make many of the simple, basic measurements which are vital to subsequent units. They should be able to distinguish between weight and mass and so realise that physics will sometimes make distinctions which are not important in ordinary life. Other quantities are also introduced or revised: density, speed/velocity, force, and moment of a force. The concept of a force field is dealt with. Other ideas include: proportionality, equilibrium, centre of mass and graphs. It should be emphasised, from this stage on, that numerical answers must include the appropriate unit. Classroom organisation and differentiation details: W: whole class; G: group; I: individual 1(d) Describe how to measure a Basic: Measuring: variety of lengths with appropriate Learners should use all the instruments in 1(d) regularly during the www.bbc.co.uk/skillswise/factsheet/ma2 accuracy using tapes, rules, course. Calculate the volume of a wooden lath 2leng-l1-f-length micrometers and, calipers using a (~50 cm × ~10 cm × ~1 cm) and use the correct instrument for each vernier as necessary. dimension. Explain that accuracy comes from the measurements not v0.7 3Y06 Cambridge O Level Physics (5054) 7 1(e) Describe how to measure a the calculator. Use calipers with inside diameter, outside diameter and Using calipers: variety of time intervals using depth gauge facility. Where possible both electronic and conventional (I G W) APPLET/ Use a stop-clock or stopwatch (learners might well have a digital watch Using a micrometer: with lap timer and timer facilities) to time pendulums or oscillating www.upscale.utoronto.ca/PVB/Harrison weights – simple graphs of period against length or mass of bob may be /Micrometer/Micrometer.html plotted. Let the learners run upstairs or in races. Calculate speeds and work done and power expended (when dealt with in the course). (G W) Make learners familiar with SI units even in the normal course of their lives. Distances in km, masses in kilograms and so on. How big is this classroom? What is the volume of air in it? (W) 1(f) Recognise and use the Basic: SI Units: conventions and symbols Wherever possible conduct the course with conventional symbols and SI 'Signs, Symbols and units. Make learners familiar with the more common prefixes: micro- (μ), ml Systematics', Association for milli- (m), kilo- (k), mega- (M). (W) Science Education, 2000. and Challenging: www.ebyte.it/library/educards/siunits/Ta Emphasise that units follow the quantity; speed is distance/time and the blesOfSiUnitsAndPrefixes.html unit of speed is the distance unit/time unit. Likewise: density is mass/volume and the unit of density is the mass unit/volume unit. Avoid –1negative index units at this level, e.g. use m/s rather than m s. (I G W) 4(a) State that mass is a measure of Basic: Mass: the amount of substance in a Explain that in physics mass is different from weight. Learners accept body. that as an object is moved around the Earth it is the same object, made astr.gsu.edu/hbase/mass.html of the same molecules in the same order and that something about it remains constant. This is the amount of matter or “stuff” it contains. and 4(b) State that mass of a body resists change from its state of rest or Explain that mass determines how difficult it is to change the motion of a www.qrg.northwestern.edu/projects/vss/motion. body (e.g. to speed it up); it determines the inertia of the body. (W) docs/space-environment/2-what-is- mass.html This unchanging quantity is called the mass and is measured in kilograms. It is the quantity one is usually interested in when buying, say, fruit or vegetables. (W) V0.7 3Y06 Cambridge O Level Physics (5054) 8 4(c) State that a gravitational field is a Basic: Weight: region in which a mass Learners readily accept that as an object journeys around the Solar www.grc.nasa.gov/WWW/k- experiences a force due to System, the force (Unit 6) of attraction to the nearest planet changes 12/airplane/weight1.html gravitational attraction. with the planet?s proximity and mass. On Earth this force is approximately and 4(d) Calculate the weight from the 10 N for every kilogram of the object?s mass. Emphasise that it varies www.mathsisfun.com/measure/weight- equation according to height above sea-level and distance from the Equator. mass.html (The actual value is usually somewhere between 9.79 N / kg and 9.83 N / kg.) (G W) Gravity: weight = mass × ;definition” of the newton is “the weight of an history/newtongrav.html average apple” – use a fruit or vegetable that the learners will be most familiar with. The actual definition is encountered in Unit 8. (W) and www.esa.int/esaSC/SEMDYI5V9ED_in Calculate learners? weights. (I G W) dex_0.html Challenging: For other planets or on the Moon; use a planet where g is larger than 10 N / kg. On the Moon it is smaller. 4(e) Explain that weights, and Lever-arm balances: Basic: therefore masses, may be www.nuffieldfoundation.org/practical-Emphasise that lever-arm balances compare unknown weights/forces compared using a balance. physics/weighing-air with the weight of a known mass. This is equivalent to comparing masses since W = mg. Would such a balance be accurate on the Top-pan balances: 4(f) Describe how to measure mass Moon? (G W) and weight by using appropriate www.csudh.edu/oliver/demos/bal- balances. use/bal-use.htm Spring balances measure the weight and deduce the mass assuming that g = 10 N / kg. This assumption is also valid on the Moon because although g is smaller is cancels out. A top pan balance, however, would need to be recalibrated on the moon. (G W) Challenging: The best way of understanding a balance is to use one; let learners see the effect of using the balance on an uneven surface, to use it when leaning on the bench or use it to measure hot objects. (I G W) 4(g) Describe how to use a measuring Basic: Measuring cylinders: cylinder to measure the volume of Learners will learn how to do this most readily by actually doing it. Get www.saburchill.com/chemistry/chaptersV0.7 3Y06 Cambridge O Level Physics (5054) 9 a liquid or solid. learners to measure the volume, mass and density of common liquids /chap0021.html such as cooking oil, orange juice etc. Use the bottom of the meniscus and for such liquids (this is the top of most of the liquid). Measure the www.msnucleus.org/membership/html/k volume of bolts and pebbles and coins (use more than one if the volume -6/as/scimath/3/assm3_5a.html is small) by immersing in water. Does immersion in oil give a different value? (I G W) Calculate the volume of wooden blocks, metal bars, and glass prisms. (I G W) Challenging: Use large and small measuring cylinders if available. Does the solid object fit into the cylinder? Use a solid that floats in water – a weight is needed to make it sink and the volume of the weight must be subtracted from the value obtained. (G W) 4(h) Describe how to determine the Basic: Density: density of a liquid, of a regularly Emphasise that volume and mass are properties of an object. They vary www.nyu.edu/pages/mathmol/modules/shaped solid and of an irregularly from object to object even when they are of the same material. Density, water/density_intro.html shaped solid which sinks in water however, is a property of the material from which the substance is made. (volume by displacement). (G W) and www.youtube.com/watch?v=Z1IMgjXin Challenging: 3U 33Emphasise the use of both g / cm and kg / m. Why does the second unit produce a value 1000 times larger? (I G) and www.cimt.plymouth.ac.uk/projects/mepr es/book7/bk7i22/bk7_22i5.htm 4(i) Make calculations using the Basic: formula density = mass/volume. There are many simple questions on this in past papers and text books. Let learners calculate m, V and ρ. V itself can be calculated from 2V = abc; πrh and so on. (I G W) 2(a) State what is meant by speed and Basic: Speed and velocity: velocity. Learners are probably familiar with these ideas from ordinary situations www.physicsclassroom.com/class/1dkin V0.7 3Y06 Cambridge O Level Physics (5054) 10 2(b) Calculate average speed using but emphasise that what they already know can be put into equation /u1l1d.cfm distance travelled/time taken. form: v = d/t and and that the unit of speed follows from the equation: km / h or m / s. www.youtube.com/watch?v=qCHnUfZ- (G W) W04 Challenging: and Explain that in physics it is important to separate speed and velocity. www.youtube.com/watch?v=C0hKJUjU Speed ignores the direction travelled but the formal distinction between ab8 scalar and vector quantities can wait. and Learners can be asked to calculate v, d and t given the other two www.youtube.com/watch?v=c4HH8vVR quantities. (I G W) fY4 6(a) State that a force may produce a Basic: Change in shape/size: change in size and shape of a Allow learners to contribute as many words as possible here: twist, www.factmonster.com/ce6/sci/A081913 body. stretch, compress, shrink, distort, contort, expand and so on. (G W) 9.html Let learners suggest their own examples of forces changing sizes and and shapes: car crashes, foam rubber, pillows and motorcycle crash www.bbc.co.uk/learningzone/clips/the- helmets. (I G W) use-of-force-to-change- shape/2489.html and www.attano.com/video/5888-Force- can-change-the-shape-of-an-object 6(b) Plot, draw and interpret Basic: Hooke?s law: extension-load graphs for an These experiments can be performed by the learners themselves. www.darvill.clara.net/enforcemot/spring elastic solid and describe the Stretch springs, rubber bands and strips of polythene – glue a piece of s.htm associated experimental wood to the bottom of the strip or use a jubilee clip and attach the procedure. weights to it. Use springs in parallel and in series. Measure and V0.7 3Y06 Cambridge O Level Physics (5054) 11 6(c) Recognise the significance of the compare the gradients of the extension-load graphs. (I G W) and term “limit of proportionality” for www.youtube.com/watch?v=pVdGUTRIan elastic solid. At this level the limit of proportionality and the elastic limit can be 49E assumed to be the same. (I G W) Elastic limit: okeslaw/elasticlimit.html and www.youtube.com/watch?v=D23hzv- 3Tf0 6(d) Calculate extensions for an Challenging: Proportionality: elastic solid using proportionality. Use T = kx or mg = kx. www.themathpage.com/ARITH/proporti onality.htm Use these equations to explain proportionality. Also use more domestic examples: Spring constant: www.4physics.com/phy_demo/HookesL the price of fruit ? the amount purchased, aw/HookesLawLab.html wages earned ? hours worked. and www.ap.smu.ca/demos/index.php?optioIn both cases, there can be different constants of proportionality: the unit price and the hourly rate. (G W) n=com_content&view=article&id=90&Ite mid=85 (Please note that mathematicians sometimes define a different quantity λ – it has different units – and call it the spring constant. In this syllabus, this quantity should never be referred to or asked for.) 5(a) Describe the moment of a force in Basic: Moments: terms of its turning effect and Learners are likely to be familiar with children of unequal weights www.bbc.co.uk/schools/ks3bitesize/scierelate this to everyday examples. balancing on see-saws. Ask how it is done. (W) nce/energy_electricity_forces/forces/rev ise8.shtml 5(d) Describe how to verify the Use a metre rule and some small masses balanced on a knife edge to verify the principle of moments. Then use it to determine the unknown principle of moments. V0.7 3Y06 Cambridge O Level Physics (5054) 12 5(b) State the principle of moments for mass of a small can. Work up through larger objects and measure the and a body in equilibrium. mass of a learner balancing on a plank. Measure the mass of the rule www.walter-fendt.de/ph14e/lever.htm by placing a weight at one end and balancing the whole arrangement at a point between the weight and the rule?s centre of mass. (I G) and , it is much better to state the alance principle using weight rather than mass: gx = mgx m1122 This is because mgx is a useful physical quantity whereas mx is not. Use traditional weighing machines and balances and the steelyard, the chemical balance and so on. Use examples with which the learners are likely to be familiar. (I G W) 5(c) Make calculations using Basic: Torque (moment): Use the principle of moments to define the moment of a force and of a force = force × emphasise it measures the turning effect of a force. Consider everyday astr.gsu.edu/hbase/torq.html perpendicular distance from the examples: spanners, wrenches, opening tins with screwdrivers and pivot spoons, the steering-wheel, door and window handles, taps, and so on. and (I G W) www.s-cool.co.uk/gcse/physics/forces-and the principle of moments. moments-and-pressure/revise- Please notice that torque is another name for moment of a force; it is it/moments also measured in N m. and The turning effect of a force is not a measurable quantity; it is just a www.cyberphysics.co.uk/topics/forces/ description of what happens when a force causes a moment. moments.htm Although the newton metre is equivalent to the joule, the joule is not usually accepted as a unit of moment and moment should not be expressed in joules. State this as a rule. (W). 5(f) Describe qualitatively the effect of Basic: Centre of mass: the position of the centre of mass Conduct experiments to show the effect. Tip a thick-bottomed glass and the stability of simple objects. a long-stemmed glass over. Place them on a book with a hard cover astr.gsu.edu/hbase/cm.html and gradually open the book; measure the angle where tipping occurs. (I G W) and www.qwerty.co.za/puzzles/mass/cofmc V0.7 3Y06 Cambridge O Level Physics (5054) 13 At this level it is hard to explain the difference between centre of mass oke.htm and centre of gravity and so it is best to use only the syllabus term centre of mass. and www.slideshare.net/danmicksee/centre- of-gravity-and-stability and www.youtube.com/watch?v=C- fZA1NJtPA and www.youtube.com/watch?v=DY3LYQv2 2qY 5(e) Describe how to determine the Basic: Centres of gravity of laminas: position of the centre of mass of a Use a variety of thick card or thin wood laminas: triangles, squares, www.mathematische-plane lamina. rectangles, pentagons, star shapes, L-shapes, O-shapes, rings and basteleien.de/geocentre.htm squares with square holes. and Cut out a map of your country printed on to thick card. Find the centre www.youtube.com/watch?v=PITFiIQjvx of gravity. Is this accurate? What about mountains, islands and lakes? w (I G W) Past paper questions: Nov 12 Paper 21 Q4 Nov 12 Paper 22 Q1 Nov 12 Paper 22 Q2 Jun 12 Paper 22 Q1 Nov 11 Paper 21 Q1 Past question papers available at: V0.7 3Y06 Cambridge O Level Physics (5054) 14 Unit 2: Waves and their uses Recommended prior knowledge Learners ought to have encountered Unit 1 before starting this unit. In addition they will need some concept of what is meant by energy, even though it need not be defined exactly at this stage. Learners should be able to use a protractor and to draw simple diagrams neatly. Words such as audible, pitch, vibration, reflection, medium, vacuum, echo, timbre, pre-natal, magnification, lens and spectrum are likely to be used without being separately defined by the teacher. Context This unit deals with waves and how they are used. It is to some extent an independent section of the syllabus with only a few other topics depending on it. Consequently those who do not wish to follow through the units in numerical order may include this unit at almost any stage. Outline The unit begins by introducing the idea of wave motion in a general sense. This is an idea which though simple at one level, is in fact sometimes difficult to grasp. When sea-waves are considered it is unlikely that much emphasis is given to their transmission of energy and this essential aspect of waves is often neglected by learners. The basic definitions are included and the idea that certain quantities may be represented by an equation is worth underlining for future use. Two specific cases, sound and light, follow on from this and the fundamental properties of all waves are studied in the context of these two examples. The practical importance of the seemingly abstract phenomenon of refraction is illustrated by the inclusion of lenses and by their use in the correction of imperfect vision. Some of the widely varying uses of electromagnetic radiation conclude this unit. Classroom organisation and differentiation details: W: whole class; G: group; I: individual 13(a) Describe what is meant by wave Basic: Waves: motion as illustrated by vibrations Energy (Unit 5) transfer often involves the net movement of matter but www.kettering.edu/~drussell/Demos/wa in ropes and springs and by for wave motion it does not. ves/wavemotion.html experiments using a ripple tank. Stretch a long spring or rope between two learners. One can transmit and energy to the other (make the second learner?s hand move) without www.youtube.com/watch?v=JXaVmUv transferring matter. wxww Point out the learners? ear drums are being moved (vibrated) without the v0.7 3Y06 Cambridge O Level Physics (5054) 15 transfer of matter. (G W) and www.bbc.co.uk/schools/gcsebitesize/sci A wave transfers energy through a medium without the medium moving ence/add_ocr_pre_2011/wave_model/ as a whole. whatarewavesrev1.shtml Use ripple tanks to show water waves transferring energy. A small piece Ripple tanks simulation: of cork vibrates as the wave passes. Compare with sound and hearing. www.falstad.com/ripple/ (G W) 13(b) State what is meant by the term Challenging: Wavefronts: wavefront. The crest line or the trough line is the wavefront. www.colorado.edu/physics/2000/waves _particles/waves.html Strictly it is a line (surface) joining points of identical phase but at this level only the best learners will understand what this means. (W) 13(d) Describe transverse and Basic: Longitudinal waves: longitudinal waves in such a way Use the long spring to show transverse waves. Get the learners to www.bbc.co.uk/schools/gcsebitesize/scias to illustrate the differences come up with longitudinal waves. (G W) ence/aqa/waves/generalwavesrev2.shtbetween them. ml Use these terms: crest, trough, compression, rarefaction, displacement and www.youtube.com/watch?v=f66syH8B9 Longitudinal waves include: sound, ultrasound, seismic P-waves, shock D8 waves. and www.youtube.com/watch?v=aguCWnb RETU Transverse waves: www.youtube.com/watch?v=AtlxBODx WHc and www.youtube.com/watch?v=P0Fi1Vcbp AI 13(c) Define the terms speed, Basic: Wave formula: frequency, wavelength and Define the terms. At this stage speed and velocity can be treated as www.gcse.com/waves/wave_speed.htm V0.7 3Y06 Cambridge O Level Physics (5054) 16 amplitude and do calculations essentially the same thing. (W) using Wave parts: Challenging: www.bbc.co.uk/schools/gcsebitesize/scivelocity = frequency × Note that the frequency is the number of waves (not necessarily ence/aqa_pre_2011/radiation/anintroduwavelength. complete waves) passing a point in unit time. Frequency is not ctiontowavesrev2.shtml necessarily an integer. (W) and Deduce the formula. (W) www.physicsclassroom.com/class/wave s/u10l2c.cfm Basic: Use the formula to deduce the speed of radio waves from the published wavelength and frequency of a local radio station. (I G W) 13(e) Describe the use of a ripple tank Basic: Ripple tank reflection: to show Show these experimentally if not in a ripple tank then in a tray of water. www.schoolphysics.co.uk/age11- (1) reflection at a plane surface (G W) 14/Wave%20properties/text/Waves_in_(2) refraction due to a change of a_ripple_tank/index.html speed at constant frequency. Draw diagrams of waves entering a shallow (slower) region at an angle. Show where the waves would have reached if the original medium had and continued and then where the waves actually are. They have skewed www.youtube.com/watch?v=HFckyHq5 around as one side slows before the other. (W) 94I Challenging: Ripple tank refraction: Comparison: caterpillar-tracked vehicles cannot steer. By slowing down www.youtube.com/watch?v=stdi6XJX6 one track and speeding up the other the vehicle skews round like waves gU refracting. Refraction: Similarly soldiers marching shoulder-to-shoulder, reach ground (at an www.nuffieldfoundation.org/practical- angle) where they travel slower. (I G W) physics/marching-model-refraction and www.youtube.com/watch?v=Tyzci1qTV L8 16(a) Describe the production of sound Basic: Production of sound: by vibrating sources. Consider: a tuning fork, a violin (or local stringed musical instrument), a www.bbc.co.uk/learningzone/clips/unde drum, vibrating rulers, cardboard strips held in the spokes of a bicycle rstanding-sound-and-16(c) State the approximate range of V0.7 3Y06 Cambridge O Level Physics (5054) 17 audible frequencies. wheel, a loudspeaker and many other examples. Learners should feel vibrations/1604.html the vibrations. (G W) 16(g) Explain how the loudness and and pitch of sound waves relate to Use a loudspeaker and a signal generator to test the frequency range of www.youtube.com/watch?v=MFLeGJclthe learners? hearing. The actual frequency range varies from person to QiI amplitude and frequency. person but a standard range of 20 ? 20 000 Hz is usually taken for a person of normal hearing. Guitar strings: www.youtube.com/watch?v=v- Test learners to discover how high a frequency a learner can detect; sARWEXReY teenage learners will already find that they cannot detect the highest frequency notes. For adults, the highest detectable frequency will be Drum: lower still. www.youtube.com/watch?v=v4ELxKKT 5Rw Make sure that the loud speaker can produce the high frequency notes. (W) Sound and the ear: www.bbc.co.uk/science/humanbody/boChallenging: dy/factfiles/hearing/hearing_animation.sUse a microphone and c.r.o. to show how the trace varies with html frequency and with amplitude. Relate these observations to pitch and loudness. (G W) and Place small particles on a drum or loudspeaker. (W) astr.gsu.edu/hbase/sound/ear.html Loudness: www.engineeringinteract.org/resources/ oceanodyssey/flash/concepts/loudness. htm and www.youtube.com/watch?v=8i6hTU0jw -g Hearing test (this will only work with loudspeakers of appropriate quality): www.youtube.com/watch?v=1yzrx84Q WqI Sound pitch, frequency and amplitude: www.youtube.com/watch?v=irqfGYD2U Kw V0.7 3Y06 Cambridge O Level Physics (5054) 18 16(b) Describe the longitudinal nature Basic: Sound waves: of sound waves and describe Use the vibrations of a loudspeaker to explain that the vibration direction www.youtube.com/watch?v=27a26e2C compression and rarefaction. is parallel to that of the sound wave. Compare this with a long spring or nuM trolleys joined by springs. (W) and www.physicsclassroom.com/class/soun d/ 16(d) Explain why a medium is required Basic: Bell jar experiment: in order to transmit sound waves Show the bell jar experiment if at all possible; the clanger can be seen www.gcse.com/waves/sound2.htm and describe an experiment to striking the bell but little or no sound is heard. (G W) demonstrate this. and Challenging: www.youtube.com/watch?v=ce7AMJdq Consider: the Sun can be seen but not heard, astronauts on a space-0Gw walk can only communicate using radio (or by touching helmets). (W) 13(f) Describe simple experiments to Basic: Speed of sound: show the reflection and refraction Demonstrate an echo from the front of a large building or cliff (~100 m www.sv.vt.edu/classes/ESM4714/Studeof sound waves. away if possible). nt_Proj/class95/physics/speed.html 16(h) Describe how the reflection of This can be extended to measure the speed of sound – use two blocks and sound may produce an echo. of wood to make a short, distinct clap or a loud whistle or a high-pitched www.youtube.com/watch?v=_1Er6v_c4 feedback sound from a megaphone. Measure the distance with rulers, 3I 16(e) Describe a direct method for the rope or a pedometer. Clapping in time with the echo from a closer wall determination of the speed of (30 m) allows the time taken for the sound to travel to the wall and back Reflection in sound: sound in air and make the to be measured more accurately. (G W) www.bbc.co.uk/learningzone/clips/the-necessary calculation. reflection-of-sound-to-produce-an- Refer to methods involving firing guns or simply observing someone clap echo/1609.html 16(f) State the order of magnitude of the two pieces of wood together from a few kilometres away. (These the speeds of sound in air, liquids rely on the speed of light being very much larger than that of sound.) and solids. (G W) Refraction in sound: www.acs.psu.edu/drussell/Demos/refra Sound travels much faster in solids and liquids. When a hammer strikes ct/refract.html a long length of metal railings, two sounds are heard: one through the railings; one through the air. (I G W) and www.youtube.com/watch?v=eHZJFa05 Quote speed of sound values for air, liquids and gases. (W) 5Xo V0.7 3Y06 Cambridge O Level Physics (5054) 19 Challenging: Speed of sound in materials: Refraction in sound can be demonstrated/described using a beach-ball www.absorblearning.com/physics/demo . This can act as a sound lens (later in this unit) and be /units/DJFPh083.html#Howfastissoundfilled with CO2used to focus sound. (Lenses work by refraction). (G W) ? If filled with He, it would be a diverging lens. (G W) and www.physicsclassroom.com/class/soun d/u11l2c.cfm 16(i) Describe the factors which Basic: Timbre: influence the quality (timbre) of Emphasise that the same note played on different instruments differ only www.youtube.com/watch?v=BLoM9bBr sound waves and how these in the shape of the trace on a c.r.o. not in their periodic times. Show this 8lc factors may be demonstrated using musical instruments, a microphone and a c.r.o. using a cathode-ray oscilloscope and (c.r.o.). Show that the amplitude does not affect the shape of the trace. (W) www.animations.physics.unsw.edu.au/j w/sound-pitch-loudness-timbre.htm 16(j) Define ultrasound. Basic: Uses of ultra sound: Define ultrasound and give a variety of uses: www.odec.ca/projects/2003/guilh3m/pu16(k) Describe the uses of ultrasound blic_html/use.html , cleaning sensitive artefacts in cleaning, quality control and , quality control, pre-natal scanning and pre-natal scanning. , distance measurers (dataloggers in universities/schools). (W) (dog whistles). (G W) and www.youtube.com/watch?v=tluZGhzg7Please note that the uses specified in the syllabus must be taught to Ks learners. 14(a) Define the terms used in Basic: Law of reflection: reflection including normal, angle These topics are best covered experimentally; learners may use mirrors incidence and angle of and ray-boxes, torches or (optical) pins. (I) astr.gsu.edu/hbase/phyopt/fermat.html reflection. Challenging: Diffuse and specular reflection: 14(b) Describe an experiment to The law may be modelled in 3D using rods or rulers to represent the www.khanacademy.org/science/physicsillustrate the law of reflection. V0.7 3Y06 Cambridge O Level Physics (5054) 20 14(d) State that for reflection, the angle rays and the normal and the desk top to act as a mirror. Observe that /waves-and-optics/v/specular-and- of incidence is equal to the angle there are many rays for which the angle of reflection equals the angle of diffuse-reflection of reflection and use this in incidence but the correct one lies in the same plane as the normal and constructions, measurements and the incident ray. Emphasise that all angles are measured between the Experiment: calculations. ray and the normal. (I G) www.youtube.com/watch?v=9aWE4rD w_ks 14(c) Describe an experiment to find Basic: Plane mirror images: the position and characteristics of Emphasise that an image is the location from which the light seems to www.youtube.com/watch?v=2ek0EsEM an optical image formed by a come. It has not actually travelled behind the mirror. An eye or a TBc plane mirror. photographic plate placed at the image position would not detect anything. For a mirror hanging on a wall, the image may well be in the and next room or building and someone there would not be able to see the www.youtube.com/watch?v=A8AfxcUN person standing in front of the mirror. (G W) vYw Challenging: Consider more complicated examples such as two mirrors at right- angles or a kaleidoscope. (I G) 14(e) Define the terms used in Refraction: Basic: refraction including angle of www.youtube.com/watch?v=OdcHCRFShow some simple examples of refraction: the bent stick, apparent incidence, angle of refraction and 00jM reduction in depth, heat haze, pass a ray of light into a tank containing refractive index. two liquids of different densities – a very small amount of paint in the and liquids will scatter light so that the path of the ray may be seen. (G W) 14(f) Describe experiments to show www.bbc.co.uk/bitesize/higher/physics/r adiation/refraction/revision/1/ refraction of light through glass Carry out experiments with a glass block and a ray-box, torch or a slit in blocks. a blind/curtain or (optical) pins. Measure i and r. Plot i ? r. Calculate Reflection and refraction: sin(i) and sin(r) and calculate sin(i)/sin(r). (I G) : 14(g) Do calculations using the Plot sin(i) ? sin(r). Measure the gradient. State that using the gradient equation gives more emphasis to those points nearest to the average behaviour. Averaging the values of sin(i)/sin(r) does not. (I G) sini/sinr = constant. Refer back to the skewing round of caterpillar tracked vehicles when the tracks are driven at different speeds. V0.7 3Y06 Cambridge O Level Physics (5054) 21 Emphasise that as the light leaves the second face of a rectangular block, it reverses the procedure which occurred at the first and emerges parallel to the incident ray. (I G W) 14(i) Describe experiments to show Challenging: Total internal reflection: total internal reflection. Explain that when a ray emerges from glass into air, the emergent angle www.cyberphysics.co.uk/topics/light/TI is larger than the angle at which it strikes the surface. In due course, it R.htm 14(h) Define the terms critical angle emerges at 90? to the lower face. If the angle at which it strikes the and total internal reflection. surface increases, then the emergent angle exceeds 90? and it passes and back into the glass. This is reflection not refraction. Refraction out of the www.youtube.com/watch?v=PrEF9UN9 glass is now impossible. (W) 8cE Emphasise the fact that two conditions must be met before T.I.R. can Critical angle: occur: www.youtube.com/watch?v=CF7CJb8X QHw 1) The light must pass from the slow to the fast medium. 2) The angle at the surface must exceed the critical angle. Fish-eye view: www.physicsclassroom.com/mmedia/o Pass a ray into the curved face of a semi-circular glass block, into the ptics/bp.cfm side face of a glass block or a tank of water. Move the ray. There comes a point at which no light at all emerges through the surface. Retroreflectors: (I G W) www.youtube.com/watch?v=ktqWZZydij Y 14(j) Describe the use of optical fibres Basic: Optical fibres: in telecommunications and state Optical fibres rely on T.I.R. Digital pulses (light/no light) transmit the www.bbc.co.uk/schools/gcsebitesize/scithe advantages of their use. information. (W) ence/edexcel_pre_2011/waves/sending informationrev1.shtml Advantages include: more information can be sent per second (many phone calls on one line), less prone to interference, less easy to tap into, fewer repeaters. and www.cyberphysics.co.uk/topics/light/Fib There are transoceanic optical fibre cables and it is possible to have an erOptics/FibreOptics.htm optical link straight into a personal computer or telephone. Challenging: Optical fibres need to be sheathed to prevent light passing from one fibre into the next. (I G) V0.7 3Y06 Cambridge O Level Physics (5054) 22 14(k) Describe the action of thin lenses Basic: Converging lenses: (both converging and diverging) Pass a ray of light from a ray-box or torch into a lens (ideally curved in www.physicsclassroom.com/class/refrn/on a beam of light. only one dimension) and observe the path of rays at different distances u14l5da.cfm from the centre. This is difficult to do with optical pins. (I G W) and 14(l) Define the term focal length. Pass a beam of parallel rays into a lens and observe the convergence. (I G W) x?dNovype=3&filename=GeometricOpti cs_ConvergingLenses.xml Define focal length. (W) and www.youtube.com/watch?v=b2h7lc2ep WA focal length: www.youtube.com/watch?v=AoGDOT6 U9pQ and astr.gsu.edu/hbase/geoopt/foclen.html 14(m) Draw ray diagrams to illustrate Image formation: Basic: the formation of real and virtual www.nuffieldfoundation.org/practical-Emphasise three special rays: images of an object by a physics/image-formation-lens (1) Incident, paraxial rays refract through the focal point. converging lens and the formation (2) Incident rays striking the optical centre emerge undeviated. of a virtual image by a diverging and (3) Incident rays which pass through or seem to have passed lens. www.physicsclassroom.com/class/refrn/through the focal point emerge paraxially. u14l5c.cfm 14(n) Define the term linear Scale diagrams will only be accurate if drawn carefully. (I G W) magnification and draw scale Linear magnification: to determine the focal Start with the object and the lens and find the image or start with the length needed for particular astr.gsu.edu/hbase/geoopt/lensdet.html object and the image and find the focal points. (I G W) values of magnification and (converging lens only). Challenging: www.youtube.com/watch?v=ZJn7nSPe(1) These three special rays are from one point on the object but all the 9_Y other rays from that point meet at (or seem to have come from) the equivalent point on the image. (2) It is usual to use the top point of the object as the object point but V0.7 3Y06 Cambridge O Level Physics (5054) 23 every other point on the object also produces an image at an equivalent position. (I G W) 14(o) Describe the use of a single lens Basic: Magnifying glass: as a magnifying glass and in a Learners can be given incomplete or unlabelled diagrams and instructed www.physics.pomona.edu/sixideas/labscamera, projector and to complete them. (I G W) /LRM/LR07.pdf photographic enlarger and draw ray diagrams to show how each Learners should know the position of the object relative to the principal Camera: forms an image. focus in the different devices. (I G W) ra1.htm It is helpful if learners have seen these devices operating or partially dismantled. Make a large model of the camera /enlarger using a and cardboard box and an appropriate lens. (G W) www.schoolphysics.co.uk/age11- 14/Light/text/Camera_/index.html Enlarger: 14(p) Draw ray diagrams to show the Basic: The eye: formation of images in the normal A model eye can be made from a fish bowl or a round-bottomed flask www.physicsclassroom.com/class/refrn/eye, a short-sighted eye and a with a lens held to the outside with a ring of modelling clay. Fill the bowl u14l6a.cfm long-sighted eye. or flask with water and a very small amount of paint to scatter the light. Pass light into the model eye. (G W) and 14(q) Describe the correction of short-www.cyberphysics.co.uk/topics/medicalsight and long-sight. Explain the causes of both short- and long-sightedness and describe the /Eye/eye.html way in which lenses are used to solve the problems. (W) Short sight: Note that although short-sightedness is sometimes called near-www.physicsclassroom.com/class/refrn/sightedness or myopia, these terms are not used in this syllabus. u14l6e.cfm Likewise, long-sightedness is sometimes called hypermetropia, but this and term is not used in this syllabus. www.youtube.com/watch?v=AsKeu4w m3XI Long sight: www.cyberphysics.co.uk/topics/medical /Eye/sightCorrection.html and V0.7 3Y06 Cambridge O Level Physics (5054) 24 www.youtube.com/watch?v=AsKeu4w m3XI Correcting problems: www.bbc.co.uk/health/physical_health/c onditions/visionproblems1.shtml 15(a) Describe the dispersion of light as Basic: Prisms: illustrated by the action on light of Best shown in practice using a glass/water prism and a ray-box, torch or www.physicsclassroom.com/class/refrn/a glass prism. slit in a blind/curtain. (I G W) u14l4a.cfm 15(b) State the colours of the spectrum Light is split up according to its wavelength. This leads to the traditional and seven colours of the spectrum/rainbow. The higher the frequency, the www.youtube.com/watch?v=NU2r-and explain how the colours are related to frequency/wavelength. greater the extent of the refraction. “Violet refracts violently” or “blue ECmPr4 bends best”. (G W) Rainbows: Use an infra-red detector (e.g. a thermometer with bulb blackened) to www.cord.edu/faculty/manning/physics detect radiation beyond the red end of the visible spectrum and show 215/studentpages/genamahlen.html that some sections of the spectrum cannot be detected by the human eye. Remember that only near infra-red can pass through normal glass. and (G W) List properties shared by all electromagnetic radiations. Include: speed in air, transverse nature, travel in vacuum. Challenging: Some learners will point out that light cannot be a wave as it does not require a medium. One might point out that magnetic and electric fields do pass through a vacuum and that light is an oscillation of such fields. (I G W) 15(c) State that all electromagnetic Basic: 8waves travel with the same high c = 3.0 × 10 m / s. speed in air and state the magnitude of that speed. V0.7 3Y06 Cambridge O Level Physics (5054) 25 15(d) Describe the main components of Basic: The electromagnetic spectrum: the electromagnetic spectrum. Emphasise that the boundaries between regions are arbitrary and ; a snake or an insect have different end wavelengths for ce/know_l1/emspectrum.html 15(e) Discuss the role of the following their visible regions. (W) components in the stated and applications: Emphasise that electromagnetic wave properties change gradually as www.bbc.co.uk/learningzone/clips/the- the frequency changes. (W) electromagnetic-spectrum/10676.html (1) radio waves: radio and television communications Avoid referring to “The seven types of electromagnetic radiation”. and (2) microwaves: satellite : television and telephone mspectrum.html (3) infra-red: household This topic provides ideal material for learner projects. The learners can electrical appliances, research these areas themselves and then talk to the rest of the class Uses of e.m. radiation: about what they have found. There is a huge amount of information television controllers and www.s-cool.co.uk/gcse/physics/uses-intruder alarms published on the internet and the difficulty is likely to be keeping it of-waves/revise-it/electromagnetic-(4) light: optical fibres in medical accurate and relevant. spectrum uses and telephone (5) ultra-violet: sunbeds, and fluorescent tubes and www.youtube.com/watch?v=snNwE6txsterilisation xP0 (6) X-rays: hospital use in medical imaging and killing cancerous cells, and engineering applications such as detecting cracks in metal (7) gamma rays: medical treatment in killing cancerous cells and engineering applications such as detecting cracks in metal Past paper questions: Nov 12 Paper 21 Q5 Nov 12 Paper 21 Q6 Jun 12 Paper 21 Q5 Jun 12 Paper 21 Q6 Jun 12 Paper 22 Q5 V0.7 3Y06 Cambridge O Level Physics (5054) 26 Past question papers available at: V0.7 3Y06 Cambridge O Level Physics (5054) 27 Unit 3: Atoms and radioactivity Recommended prior knowledge Learners will have heard about atoms and electrons but are very unlikely to have a very clear idea of what they are. It would be helpful if learners had already encountered atoms as building-bricks in chemistry and had some conception of just how small they are. Similarly, learners will have met electric charge in more domestic circumstances but this quantity is not properly encountered until the next unit and teachers should be aware that, for learners, it is not necessarily a fully understood branch of the subject. Element, ionising and random are words which might well be used freely by the teacher whilst remaining something of a mystery to the learners. The word radioactive will have been encountered mostly in negative and dangerous contexts. Furthermore, some learners will not realise that the Sun is just an ordinary star and this ought to be stated specifically in the final sections. Context This unit deals with the structure of ordinary matter and as a result it presents ideas which are vital in many scientific contexts ranging from engineering and materials science to pharmacology. The ideas included will be fundamental to many other sections of the syllabus and if the numerical order of units is not followed, the first parts of this unit must be dealt with at an early stage. Outline The first half of this unit describes the structure of an atom and the evidence for the nuclear theory. Learners learn about the three constituent particles which make up atoms and their arrangement within it. Terms like isotope will be explained. The second half deals with radioactivity and the properties of alpha-, beta- and gamma-radiation. The fission of large atoms and the fusion of hydrogen atoms in stars will be explained and, then, some elementary mathematics is needed for the definition of half-life and is used in calculations. Classroom organisation and differentiation details: W: whole class; G: group; I: individual 27(a) Describe the structure of the atom Basic: Electrons: in terms of nucleus and electrons. Learners have probably heard of atoms and that there are roughly 90 www.aip.org/history/electron/ different types which combine to make all substances. They have probably heard about electrons. State that these particles and are small objects which carry negative charge. They are important in: www.youtube.com/watch?v=ky1Awa0p ionisation (chemistry), electrostatics (Unit 4), current electricity (Unit 4), J0s v0.7 3Y06 Cambridge O Level Physics (5054) 28 electrolysis (chemistry), beta-emission (26(a)) and thermionic emission (Unit 10). (W) Atomic structure: www.purchon.com/chemistry/atoms.htm Electrons occur in: electrical conduction in gases and electrical and thermal conduction in metals (Unit 5). Some of these effects are found and in all substances. Electrons are fundamental particles. There are www.bbc.co.uk/schools/gcsebitesize/sci electrons in all atoms. ence/add_aqa_pre_2011/atomic/atomst rucrev1.shtml and www.youtube.com/watch?v=jRVjDKesn Y4 27(b) Describe how the Geiger-Basic: Marsden alpha scattering Describe the experiment. Three possible results: experiment provides evidence for the nuclear atom. (1) Nearly all alpha particles pass straight through. The atom is almost entirely empty space. (2) A few particles are deflected through noticeable angles. There is something in the foil. (3) A very few particles rebound through very large angles. There is something in the foil which is very small, very dense and repels alpha particles (positive). (W) Emphasise the extreme inequality in the distribution of matter within the –12 % of the volume. atom. ~99.95 % of the mass is concentrated in ~10 Use a local comparison. E.g. a pea in a local football stadium. (W) 27(c) Describe the composition of the Basic: The nuclear atom: nucleus in terms of protons and Since the electrons are negative and easy to remove (electrostatics, www.nuffieldfoundation.org/practical-neutrons. ionisation, thermionic emission), they must be in the outer orbits and physics/developing-model-atom- keep atoms apart. The nucleus is the dense and positive centre of the nuclear-atom atom. State that the nucleus is made up of positive and neutral particles of very similar mass. These are protons and neutrons. (W) Protons and neutrons: www.bbc.co.uk/schools/gcsebitesize/sci The helium nucleus is four times more massive than that of hydrogen ence/add_ocr_pre_2011/periodic_table/ but has only twice the charge. The neutral particles keeping the two atomicstructurerev1.shtml protons apart also have mass. (W) V0.7 3Y06 Cambridge O Level Physics (5054) 29 27(d) Define the terms proton number Basic: Isotopes: (atomic number), Z and nucleon The proton number determines the number of electrons in the neutral www.colorado.edu/physics/2000/isotopnumber (mass number), A. atom and so it determines the chemical properties of that substance. It es/index.html is the atomic number. (W) and 27(f) Define the term isotope. All carbon atoms have 6 protons and all atoms with 6 protons are carbon and so on. astr.gsu.edu/hbase/nuclear/nucnot.html 27(g) Explain, using nuclide notation, how one element may have a The nucleon number determines the mass of the nucleus and is and number of isotopes. sometimes called the mass number. Avoid the term “neutron number” www.chem4kids.com/files/atom_isotope as it is easily confused with “nucleon number”. (W) s.html Challenging: Two atoms with the same proton number may have a different number of neutrons. They have the same chemical properties (because they have the same number of electrons in a neutral atom) but are not identical. They are different isotopes of the same atom. Emphasise that the proton number alone determines the chemical 1213properties. C and C are identical chemically. (Or use another example.) 1213C and C are both isotopes of carbon. Use the nuclide notation here before radioactivity is mentioned. (G W) 26(k) Describe how radioactive Basic: Radioactive safety: materials are handled, used and Explain dangers of nuclear radiation, include: burns, sickness, biological www.bbc.co.uk/schools/gcsebitesize/scstored in a safe way. cell damage, cancer, cell mutation. (W) ience/ocr_gateway_pre_2011/living_fut ure/4_nuclear_radiation4.shtml Rules include: use the minimum activity, keep your distance, insert protective layers. It is essential to state the rules and to obey them. Emphasise that alpha-, beta- and gamma-radiation do not make other materials radioactive when they are absorbed. (W) 26(a) Describe the detection of alpha-Basic: Detecting radiation: particles, beta-particles and Where possible, bring radioactive samples near to a GM tube or a spark www.darvill.clara.net/nucrad/detect.htm V0.7 3Y06 Cambridge O Level Physics (5054) 30 gamma-rays by appropriate counter. Use an old, luminous watch or altimeter or suitable rocks if methods. educational samples are not available. Such substances are emitting and something. (G W) www.bbc.co.uk/schools/gcsebitesize/sci ence/aqa_pre_2011/radiation/radioactiv The radiations can also be detected by a variety of devices. Only one erev5.shtml method of detection needs to be learnt by the learners. Cloud chamber: Challenging: www.youtube.com/watch?v=ItdSjJKmy State that some substances cause the exposure of nearby photographic DY plates – this was how radioactivity was discovered. Describe the tracks in a cloud chamber. 26(c) State for radioactive emissions, Basic: Radiation properties: their nature, relative ionising Where possible use a mixed source and show that there are three types www.physics.isu.edu/radinf/properties.heffects and relative penetrating of emission which have distinct properties: tm powers. and Alpha (,) heavily ionising but easily absorbed. 26(d) Describe the deflection of (,) less ionising but less easily absorbed. training/radiationproperties/radiationproradioactive emissions in electric Gamma (,) weakly ionising but difficult to absorb completely. fields and magnetic fields. perties.htm Tabulate the properties of the three types of radiation. Include: Electric field effect: particle/wave, charge, mass, ionising strength, penetration strength, www.youtube.com/watch?v=ZlFz3AAwnature, behaviour in electric and magnetic fields. (W) wBQ Magnetic field effect: www.youtube.com/watch?v=adGVpHvE yUU 26(b) State and explain the random Basic: Random emission: emission of radioactivity in Measure the count-rate from a source (background radiation will do). www.physicsdaily.com/physics/Random direction and time. Notice that it varies about an average value. and Emphasise that whilst random events are utterly unpredictable individually, on a sufficiently large scale, the behaviour is very accurately ties/PennyDecay.html predictable. (G W) (Half-life ideas lead learners to imagine that the number of atoms falls in some manner such as this: 160 ? 80 ? 40 ? 20 ? 10 ? what and V0.7 3Y06 Cambridge O Level Physics (5054) 31 happens now? With numbers this small, of course, the behaviour is www.youtube.com/watch?v=Utpi5rFSV unpredictable). e0 Challenging: Life assurance works on a similar basis. Individual deaths are unpredictable but with a large enough number of customers, the likely number of deaths in a given time varies very little. (G W) 26(e) Explain what is meant by Basic: Radioactive decay: radioactive decay. Learners should know that radioactive decay is the random emission of ~mmp/a alpha-, beta- or gamma-radiation from unstable nuclei. (G W) pplist/decay/decay.htm The emissions are unaffected by temperature, pressure and chemical and combination. (W) www.bbc.co.uk/schools/gcsebitesize/sci ence/add_aqa_pre_2011/radiation/atom At first, consider only two types of radioactive decay: alpha and beta. sisotopesrev3.shtml Then explain that these may occur on their own or with gamma. (W) . 27(e) Explain the term nuclide and use Challenging: Nuclide notation: When explaining this notation, make it clear that the element X www.youtube.com/watch?v=nLIgVpTFthe notation X to construct determines what the number Z is and vice versa. E.g. if Z = 7, then X is oFo equations where radioactive always an N (nitrogen). (G W) decay leads to changes in the composition of the nucleus. The equation for the alpha decay of, say, U is fairly straightforward. Emphasise that in beta emission a nuclear reaction occurs first: +?n ? p + e. Hence, the superscript and subscript, in e, are present to balance the equation. A beta-particle is not made of ?1 proton. Emphasise that after the emission of an alpha- or beta-particle, the nucleus may rearrange itself and emit an electromagnetic wave (gamma-ray). No particle is emitted. (G W) Notation such as, may confuse learners. 26(f) Explain the processes of fission. Avoid explaining fission and fusion together. The words are very similar Fission: V0.7 3Y06 Cambridge O Level Physics (5054) 32 26(g) Describe with the aid of a block but the processes are essentially the reverse of each other. diagram one type of fission astr.gsu.edu/hbase/nucene/fission.html reactor for use in a power station. Basic: and State that U is explosively radioactive. Bombarding U with neutrons www.youtube.com/watch?v=kHXMiYsFmay produce this isotope which may lead to a chain reaction. SrU (W) and A nuclear power station is like a standard steam turbine station powered www.youtube.com/watch?v=hKhYc9c2by coal, oil or gas. It is simply that the mechanism for boiling the water Aqs is different. (G W) Nuclear power stations: A block diagram can be drawn as a project in groups and the best group www.technologystudent.com/energy1/nthen explains the operation of a nuclear power station to the class. uclear1.htm Challenging: The chain reaction can be modelled with a vertical array of horizontal matches. Light the lowest match but it is too far away from the ones above to ignite them. If a second array of matches interpenetrates the first, distances are reduced and they can all ignite from the bottom upwards. (W) 26(m) Discuss the origins and effect of Basic: Background radiation: background radiation. Measure the count-rate in the laboratory. It is never zero. Two sources: www.darvill.clara.net/nucrad/sources.ht natural background radiation – rocks and space. (I G W) m Man-made exposure – medical diagnosis (include X-rays but emphasise and that they are not actually nuclear in origin), medical treatment, power www.bbc.co.uk/schools/gcsebitesize/sci stations, military tests, flying, travel to areas with higher levels and so ence/ocr_gateway_pre_2011/living_futu on. (W) re/4_nuclear_radiation2.shtml There are risks with all levels of exposure and the risk increases with the and absorbed dose. Even the highest natural levels seem to pose few health www.youtube.com/watch?v=TdbzShLU risks. (W) 30w Challenging: Learners find it difficult to understand that risky procedures are used in hospitals until it is pointed out that most medical procedures (e.g. cutting holes into a patient) involve some risk but that the treatment is usually V0.7 3Y06 Cambridge O Level Physics (5054) 33 less hazardous than the disease. (W) 26(i) Explain what is meant by the term Half-life: Challenging: half-life atoms and has Quote a specific example: 1 kg of U contains ~2.5×10astr.gsu.edu/hbase/nuclear/halfli.html 724an activity of ~1.2×1026(j) Make calculations based on half- Bq. 2 kg is made of ~5.0×10 atoms and has an 7and life which might involve activity of ~2.4×10 Bq etc. Therefore A , N. Draw the graph of information in tables or shown by www.bbc.co.uk/schools/gcsebitesize/sciN ? t. As the value of N falls so does the rate at which it is falling. This decay curves. ence/aqa_pre_2011/radiation/radioactivgraph has the familiar property of halving in a certain constant time. (W) erev7.shtml Carry out a standard school laboratory determination of half-life or show and videos/DVDs of such experiments. Learners plot the graph and www.youtube.com/watch?v=214cwT4vcalculate the answer. (I G W) 3D8 Paint one face of a large number of small cubes a distinct colour. Model Half-life calculations: decay by throwing the cubes from a beaker on to the desk and removing www.darvill.clara.net/nucrad/hlife.htm those which land with the painted face upwards. Repeat many times. Plot number of cubes left ? number of the throw. (I G W) Carry out calculations. Only use whole numbers of half-lives but problems which require a background count correction should be included. Half-lives encompass a very wide range of values: billions of years to milliseconds. (I G W) Emphasise that the constant time for halving does not depend on the start point. It also takes one half-life to fall from 80% to 40% or from 96% to 48%. Consequently in half-life experiments, the clock can be started at any convenient value. (W) Basic: Plot height of water in a burette ? time after opening tap. This does not give a particularly good curve (because of surface tension) but at least the height does decrease at a decreasing rate. (I G W) 26(l) Discuss the way in which the type Basic: Uses of radiation: of radiation emitted and the half-There are many examples but these include: www.bbc.co.uk/schools/gcsebitesize/scilife determine the use for the ence/ocr_gateway_pre_2011/living_futu, Alpha emitters are used to deliver radiation locally in medical material. re/4_nuclear_radiation2.shtml procedures (e.g. to a tumour inside the brain) and in smoke V0.7 3Y06 Cambridge O Level Physics (5054) 34 detectors. and www.darvill.clara.net/nucrad/uses.htm , Beta emitters are used when determining the thickness of paper as it is manufactured and the level of fruit juice in a and carton. www.gcsescience.com/prad24- radioactivity-uses.htm , Gamma emitters are used when radiation has to leave the human body to be detected for diagnosis or when treating internal organs from outside. The half-life must be long enough for the procedure to be accurate but not so long that is constitutes a health hazard. There are so many examples that it is important to make it clear why a certain procedure needs the particular properties of the radiation chosen and why the others would not be effective. (W) Learners can work in groups and prepare a lesson on one particular use and explain it to the class (~20 min. per use). 26(n) Discuss the dating of objects by Challenging: Radiocarbon dating: 1414C. Emphasise that C is continuously produced in the upper atmosphere the use of www.c14dating.com and passes into living things through photosynthesis and digestion; it only occurs in things which were once alive including: wood, bones, and seeds. Learners can be unsure about which things were once alive. Its ~5730 y and after about 20 000 y, the dating is less accurate g/radiocarbon.htm 14as little C is left. (W) and Very challenging: www.youtube.com/watch?v=GfiNewvZThe process has to be corrected for fluctuations in the prevailing level of A4I 14C. This is done using the tree rings of ancient redwood trees – dendrochronology. (I G) 26(f)2 Explain the processes of fusion. Basic: Nuclear fusion: Emphasise that the Sun and all stars have burnt for too long and given www.jet.efda.org/pages/content/fusion1 off too much energy for their power source to be chemical. It is now .html V0.7 3Y06 Cambridge O Level Physics (5054) 35 26(h) Discuss theories of star formation known that it is powered by four hydrogen atoms merging into one and their energy production by helium atom. This process is highly exothermic. (W) and fusion. www.bbc.co.uk/schools/gcsebitesize/sci Learners should know that: 2 H + 2 H ? He + energy (in some way). ence/add_aqa_pre_2011/radiation/nucl (W) earfissionrev2.shtml Challenging: and Stars are formed when clouds of gas and dust collapse under gravity, www.frankswebspace.org.uk/ScienceA the temperature increases until the hydrogen nuclei can fuse. Stars are ndMaths/physics/physicsGCSE/nuclear in balance when the pressure caused by the fusion reaction balances Fusion.htm that caused by gravitational attraction. (W) Star formation: Emphasise that both the fusion of small nuclei and the fission of large www.s- ones release energy. A different rule applies at the two ends of the cool.co.uk/gcse/physics/space/revise- periodic table (W) it/life-of-stars and www.gcse.com/eb/star1.htm. Past paper questions: Nov 12 Paper 22 Q7 Nov 12 Paper 22 Q8 Nov 11 Paper 21 Q8 Jun 11 Paper 22 Q8 Nov10 Paper 22 Q7 Past question papers available at: V0.7 3Y06 Cambridge O Level Physics (5054) 36 Unit 4: Moving charges Recommended prior knowledge Learners will need to have encountered electrons and should know where they are to be found in the atom. Learners are likely to have some basic understanding of electrostatic charging and this will be useful in coming to grips with electric charge in a more general manner. That charge comes in two distinct types which may cancel out is also worth explaining as, frequently, it is just assumed to be true. It would be useful if learners had encountered the idea of electric current in some domestic or more elementary way before it is properly defined here. Context This very substantial unit is an absolutely essential preliminary for the topics which are met in Units 7 and 10. Electricity is a major constituent of any physics course and it is here that the most fundamental ideas are initially explained. Learners do not find these ideas easy or self-evident and so this unit needs to be tackled with particular care. Outline The early sections deal with electrostatic charge and some situations in which it is found. The fundamental link between charge and electrons is made explicit at this stage. The electric field can be treated as another field of force and the idea of force lines can be introduced quite naturally with it. The distinction between conductors and insulators is drawn and this leads directly into the relationship between charge and current. The ampere is defined in some imprecise way at this point. This opens up the topic of electrical circuits and all the fundamental ideas follow from the concept of an electric current. E.m.f. and p.d. are introduced, and power and resistance are defined here. Learners will also become very familiar with circuit diagrams and the symbols for many essential conducting components. This is a large and important unit and it should not be rushed. Classroom organisation and differentiation details: W: whole class; G: group; I: individual 18(a) Describe experiments to show Electrostatic experiments are best included in the curriculum at a time Theatre of Electricity: electrostatic charging by friction. when the climate is likely to be less humid and the air dry and warm. www.mos.org/sln/toe/toe.html Basic: Use a rubbed, insulating rod to deflect a trickle of water, make hair stand Van de Graaf generator: on end, pick up dust and small pieces of paper. Rub a balloon and it sticks www.howstuffworks.com/vdg.htm to the wall. (I G W) v0.7 3Y06 Cambridge O Level Physics (5054) 37 Recall that clothing sticks to your back on dry days, that walking on nylon carpets, leaving cars and touching TV screens causes small electric and shocks. A tingling sensation is felt before lightning storms. Use local www.youtube.com/watch?v=sy05B32X examples with which the learner will be familiar as climate has an effect. TYY (I G W) Use a Van de Graaf generator to show electrostatic effects. This high voltage device must only be used by a qualified operator and under conditions of the strictest safety. Ensure that any learner involved does not have a medical heart condition or other condition preventing them from taking part. (W) 18(d) State that unlike charges attract Basic: The Gold-Leaf Electroscope: and that like charges repel. These effects are most easily shown by balancing charged rods on a lens www.youtube.com/watch?v=5j4piAI_ig or watch glass. Nylon and cellulose acetate are much easier to use than E glass and ebonite). (I G W) The Basic Law: Use a gold-leaf electroscope to show repulsion of the leaf. (I G W) www.youtube.com/watch?v=F6v8wm7_ vdQ The gold-leaf electroscope is not mentioned in the syllabus but it does show several aspects of electrostatics fairly easily. 18(c) State that there are positive and Basic: Types of charge: negative charges and that Use several different charged rods. There are only two types of behaviour www.physicsclassroom.com/class/estaticharge is measured in and only two types of charge. (I G W) cs/u8l1c.cfm coulombs. Use two rods of different materials together to show a reduced effect. and (I G W) www.youtube.com/watch?v=45AAIl9_ls c One type of charge cancels the other and so they may be called positive and negative. (I G W) Challenging: Set up a series circuit with an EHT supply, two separated metal plates and a very sensitive galvanometer or coulombmeter. A table-tennis ball (with a conducting coating) shuttles between the two plates and a reading is recorded. The high voltage EHT supply must only be used by a qualified operator and under conditions of the strictest safety. (W) V0.7 3Y06 Cambridge O Level Physics (5054) 38 18(b) Explain that charging of solids Basic: Charging by friction: involves a movement of State this as a fact. Learners have probably heard of electrons (even if www.physicsclassroom.com/class/estatielectrons. Unit 3 has not been taught) and know they are negative. cs/u8l2a.cfm Emphasise that the negative charges move and that positive objects have and lost electrons. (W) www.youtube.com/watch?v=d1RbFxTp n_g A can containing a duster is on a gold-leaf electroscope. Take a nylon rod from the can which rubs against the duster. The leaf deflects. Reinsert the rod. The deflection collapses. Hence the positive charge on one object is equal to the negative charge on the other. (I G W) 18(e) Describe an electric field as a Basic: Electric field: region in which an electric Emphasise the idea that actions occur near to a charged object: pick up experiences a force. small pieces of paper, dust on polished glass, clothing sticks to back, astr.gsu.edu/hbase/electric/elefie.html crackling near overhead power cables. and www.youtube.com/watch?v=WcSSWN4 Tnoo 18(f) State the direction of lines of Basic: Plotting field patterns: force and describe simple field Plot field patterns with EHT supply, electrodes and semolina grains in www.physicslab.co.uk/Efield.htm patterns. cooking oil. The high voltage EHT supply must only be used by a qualified operator and under conditions of the strictest safety. (W) Electric fields: www.colorado.edu/physics/2000/waves Avoid comparing electric and magnetic fields at this early stage, it _particles/wavpart3.html confuses. Learners can become adept at drawing electrostatic fields. (I G W) Give them a few rules: , field lines do not cross , field line leave conductors at right angles , arrows point from + to –. Try: ball to ball, plate to plate, ball to plate, cloud to city skyline/trees/ cars. V0.7 3Y06 Cambridge O Level Physics (5054) 39 18(g) Describe the separation of Basic: Electrostatic Induction: charges by induction. Two metal balls on insulating stands are touching. Bring a rod near to www.s-cool.co.uk/gcse/physics/static- one ball. Separate the balls and check the charges using a gold-leaf and-current-electricity/revise-it/static- electroscope. (I G W) electricity Challenging: and Charge a gold-leaf electroscope itself by induction. (I G W) www.youtube.com/watch?v=U3mxRST edeY 18(h) Discuss the differences Basic: Conductors and insulators: between electrical conductors Use a low voltage d.c. circuit with a lamp to test common materials. www.ndt- and insulators and state (I G W) ed.org/EducationResources/HighSchool examples of each. /Electricity/conductorsinsulators.htm Try to discharge a gold-leaf electroscope through these common 18(i) State what is meant by materials. Can the charge pass through people? (I G W) Earthing: www.youtube.com/watch?v=NK-“earthing” a charged object. Do not try to pass electric currents through people. BxowMIfg Standing on a rubber sheet or polythene bag and repeat. (I G W) Learners will see that the nearly all the best electrical conductors are metals. Notice that wood does not conduct a current but does discharge an electroscope. Never use a wooden object to rescue someone who is being electrocuted. 18(j) Describe examples where Basic: Lightning: charging could be a problem, Spark hazard: www.fi.edu/weather/lightning/science.ht e.g. lightning. (1) On oil tankers sailors wear special conducting shoes. ml (2) Aeroplanes and filling station tanks are electrically connected to the tanker when being filled with fuel. and (3) Small shocks in cars or large carpeted shops. www.sciencemadesimple.co.uk/page17 9g.html Conductors solve these problems, e.g. slightly conducting aeroplane tyres discharge landing planes slowly, lightning conductors. (I G W) V0.7 3Y06 Cambridge O Level Physics (5054) 40 18(k) Describe examples where Challenging: Photocopier: charging is helpful, e.g. Explain how these devices work. Learners can be given sheets with www.bbc.co.uk/schools/gcsebitesize/sciphotocopier and electrostatic printed diagrams of different stages in the procedure and can label or ence/add_gateway_pre_2011/radiation/precipitator. complete them. (I G W) electrostaticsusesrev1.shtml Concentrate on the charge placed on the photosensitive drum surface and Electrostatic precipitator: how light enables it to be removed. www.frankswebspace.org.uk/ScienceA ndMaths/physics/physicsGCSE/usingSt In a photocopier, a mirror image is formed twice which restores the atic.htm original pattern. This is an interesting occurrence in its own right. Use as the image something which lacks left/right and top/bottom symmetry. E.g. Electrostatic spraying: a large letter F, L or R. www.youtube.com/watch?v=leapiWpg0 Gc and www.slideshare.net/awkf2000/16-static- electricity 19(a) State that a current is a flow of Basic: Electric current: charge and that current is Refer to the shuttling ball experiment. Set up a series circuit with an in amperes. ammeter, large resistance and a coulombmeter. Plot charge ? time. (W) astr.gsu.edu/hbase/electric/elecur.html 20(b) State that the current at every Use a larger current. and point in a series circuit is the www.physicsclassroom.com/class/circuisame, and use this in Emphasise that a current is a “loop flow” of charge which is the ts/u9l2c.cfm calculations. mechanism for energy (not properly defined until Unit 6) transfer. The bicycle chain is a reasonably good analogy for a current. and 20(d) State that the current from the www.bbc.co.uk/schools/ks3bitesize/sciesource is the sum of the Allow learners to predict how current varies at different places in a series nce/energy_electricity_forces/electric_ccurrents in the separate circuit. Then allow them to test their predictions. (I G W) urrent_voltage/revise1.shtml branches of a parallel circuit. Use the word current rather than amperage. Challenging: Measure the current in different branches of parallel circuits. Currents split but the total remains the same. Change the resistance of some branches. Compare with water in supply pipes or the movement of the links in a bicycle chain. (I G W) V0.7 3Y06 Cambridge O Level Physics (5054) 41 19(b) Do calculations using the Basic: Current and charge: equation At this stage it is easier to define the ampere as the coulomb/second www.youtube.com/watch?v=AIkT78RR rather than the more accurate reverse definition. (W) M5Q charge = current × time. Some learners find rearranging equations hard, even though in more and everyday examples – e.g. 50 km / h for 2 h, distance travelled = 100 km – there seems to be no problem. as-a2/current-electricity/charge-current- potential-difference/ Explain that a charged battery stores a certain amount of charge. It can supply 20 A for 2 h or 10 A for 4 h etc. A flat battery cannot supply charge. (I G W) 19(c) Describe the use of an ammeter Basic: Using a multimeter: with different ranges. This will be covered as learners use ammeters in different experiments. www.dNovronics.co.uk/meter.htm Learners should know how to use the ammeters they deal with. There is no substitute for experience with the meters themselves. (I G W) and www.youtube.com/watch?v=bF3OyQ3 HwfU 19(d) Explain that electromotive force Basic; Difference between e.m.f and p.d: (e.m.f.) is measured by the First explain that e.m.f. is the property of a source of electrical energy, www.nuffieldfoundation.org/practical- energy dissipated by a source in include: cells, generators. (W) physics/potential-difference-and-emf driving a unit charge around a complete circuit. If a circuit is left on for twice as long it transfers, twice as much energy Energy and voltage: and twice as much charge flows in the circuit (Unit 5). Hence www.bbc.co.uk/bitesize/higher/physics/ energy/charge is a constant. (W) elect/energy_volts/revision/3/ Heat water in a polystyrene cup with a low voltage (this word is hard to and avoid) immersion heater. Plot temperature ? time; this is equivalent to energy ? charge. (I G W) astr.gsu.edu/hbase/electric/elevol.html 19(e) State that e.m.f. is work Challenging: P.d: done/charge. There are a variety of analogies possible for this difficult idea: www.physicsclassroom.com/class/circui V0.7 3Y06 Cambridge O Level Physics (5054) 42 19(f) State that the volt is given by ts/u9l1c.cfm J/C. The Coulomb Brothers carry sacks of joules around the circuit. They drop the joules off at the appliance and return with an empty sack. and (G W) www.youtube.com/watch?v=- 2epDX0mF4I There is a fixed number of joules/coulomb. (W) Coal lorries/trains travel in a continuous loop from the coal mine to the power station and travel back empty. There is a fixed amount of energy per lorry. (W) 19(g) Calculate the total e.m.f. where Basic: Cells in series and parallel: several sources are arranged in www.batteryuniversity.com/partone-Carry out the measurement with a voltmeter. (I G W) series and discuss how this is 24.htm used in the design of batteries. Consider car batteries (6 × 2.0 V) and PP9s (6 × 1.5 V). Keep a PP9 which has been sawn in half and show the six layers. (W) 19(h) Discuss the advantage of Basic: Several cells in parallel: making a battery from several Refer back to 20(d). Charge up a model lead-acid cell for a few minutes. www.allaboutcircuits.com/vol_6/chpt_3/ equal voltage sources of e.m.f. Discharge it through a torch lamp and time how long it takes. Repeat with 3.html arranged in parallel. two lead cells in parallel, each of which was charged for the same time and with the same current as the previous cell. (I G W) and eryday-tech/battery6.htm 19(i) State that the potential Challenging: Potential difference: difference (p.d.) across a circuit This can be done by referring back to the definition of e.m.f. The p.d. www.regentsprep.org/Regents/physics/ component is measured in volts. however, is concerned with where the energy ends up, not where it comes phys03/apotdif/default.htm from. (W) and 19(j) State that the p.d. across a component in a circuit is given www.bbc.co.uk/schools/gcsebitesize/de by the work done in the sign/electronics/calculationsrev1.shtml component/charge passed through the component. 19(k) Describe the use of a voltmeter Basic: Using a multimeter: with different ranges. Learners learn how to use the meters to which they have access by www.dNovronics.co.uk/meter.htm carrying out their own experiments. (I G) V0.7 3Y06 Cambridge O Level Physics (5054) 43 19(l) State that Basic: The Ohm Law: , plot V ? I. resistance = p.d./current Measure the gradient. State “This is a 50 V/A conductor” or whatever hms-law value it is. Repeat with other values and plot on the same axes. “These and use the equation and are 20 V/A or 10 V/A conductors.” (I G) resistance = voltage/current astr.gsu.edu/hbase/electric/ohmlaw.htmThis value tells us how hard it is to send a current through the conductor. l The 50 V/A is offers more resistance than the 10 V/A. Resistance is in calculations. measured in V/A – also called the ohm, ,. and www.youtube.com/watch?v=uLU4LtG019(m) Describe an experiment to measure the resistance of a _hc metallic conductor using a Current and voltage: make the necessary calculations. 19(q) Describe the effect of Basic: Temperature dependence of resistance: temperature increase on the (Temperature is not covered until Unit 6 but learners are likely to be aware respective sketch graphs of www.youtube.com/watch?v=rNsykkSR3of elementary kinetic theory). (I G) current/voltage. wg and Challenging: 19(n) Discuss the temperature www.youtube.com/watch?v=LeOTKXBWhen filament bulbs blow, why is it when they are switched on? The limitations on Ohm?s Law. M5KI current surge occurs because the resistance is low when they are switched on. (I G W) Use an ohmmeter to measure the resistance of a small low voltage bulb (e.g. 6 V) heated up in a water bath or sprayed with a cooling spray. It requires a little time for the bulb?s filament to reach any temperature outside. (I G W) V0.7 3Y06 Cambridge O Level Physics (5054) 44 19(o) Use quantitatively the Basic: Dependence on length and area: proportionality between www.regentsprep.org/Regents/physics/Plot V ? I for wires of different lengths and compare gradients. Or use resistance and the length and an ohmmeter. Use a poor conductor with a significant resistance for a phys03/bresist/default.htm the cross-sectional area of a short length. Plot R ? x. (I G) wire. and Repeat for different cross-sectional areas. (I G) www.youtube.com/watch?v=R4qFnKnZ EOA Use conducting putty which can be extruded into cylinders of different cross-sectional areas and different lengths. (I G W) and www.youtube.com/watch?v=xg2pEzP- mlQ 19(p) Calculate the net effect of a Basic: Resistors in parallel and series: number of resistors in series (I G) and parallel. sistors/Default.htm Emphasise: and , A thick wire is just many thin ones laid side by side. , A long wire is just many short ones laid end to end. its.html Challenging: Measure the resistance of networks made of n parallel branches of n resistors. How hot do the resistors get? Why do they not get as hot? (I G W) 19(r) Describe the operation of a Basic: LDRs: light-dependent resistor (LDR). Measure R at different light intensities for a LDR. It is difficult to measure www.dNovronics.co.uk/ldr_sensors.htm the intensity easily or accurately but definite fractions of a standard intensity can be used by letting the light pass through a variable aperture. and E.g. cut ever bigger holes in a piece of cardboard. www.bbc.co.uk/schools/gcsebitesize/de (I G W) sign/electronics/componentsrev4.shtml V0.7 3Y06 Cambridge O Level Physics (5054) 45 20(a) Draw circuit diagrams with Basic: Circuit symbols: power sources (cell, battery or These symbols are best learnt gradually in the course of describing www.gcse.com/circuit_symbols.htm a.c. mains), switches (closed experiments or when learners write them up. and open), resistors (fixed and and variable), light-dependent It is not a good idea to produce a sheet containing all the symbols at the www.bbc.co.uk/schools/gcsebitesize/sciresistors, thermistors, lamps, beginning of this section; this generates confusion. ence/add_aqa/electricity/circuitsrev1.shtammeters, voltmeters, ml magnetising coils, bells, fuses, The teacher might, however, keep a record of the symbols encountered relays, light-emitting diodes and by the learners as the course progresses and give out a full sheet when rectifying diodes. they have all been encountered separately. Challenging: Rectifying diodes do not feature largely elsewhere in this syllabus and it might be sensible to investigate their conduction characteristics at this point. This can be done simply with a d.c. ammeter or a c.r.o. can be used and the effect of an a.c. looked at. (G W) 20(c) State that the sum of the Basic: p.d.s in series: potential differences in a series Reminder: p.d. is concerned with where the energy ends up. Consider www.bbc.co.uk/schools/gcsebitesize/scicircuit is the equal to the two resistors (AB and BC) in series. The energy which ends up between ence/add_ocr_pre_2011/electric_circuitpotential difference across the terminal A and C (i.e. in the two resistors) is equal to that which ends up s/parallelandseriesrev3.shtml whole circuit and use this in between A and B added to that between B and C. (W) calculations. Set up a series circuit and show this. Use the opportunity to include a section of circuit with resistors in parallel. Note these resistors all have the full p.d. of that section of the circuit across them which only counts once when finding the total p.d. across the circuit. (I G W) 20(e) Do calculations on the whole Basic/challenging: Resistance: circuit, recalling and using Learners will need to practise answering questions starting with simple formulae including circuits (one cell, one ammeter and one resistor) and gradually try more astr.gsu.edu/hbase/electric/resis.html complicated arrangements as they become more proficient. (I G W) and R = V/ I www.physicsclassroom.com/class/circui ts/u9l3b.cfm and those for potential differences in series, resistors in series and resistors in parallel. V0.7 3Y06 Cambridge O Level Physics (5054) 46 Past paper questions: Nov 12 Paper 21 Q7 Jun 12 Paper 21 Q7 Jun 12 Paper 22 Q7 Nov 11 Paper 21 Q5 Nov 11 Paper 22 Q6 Past question papers available at: V0.7 3Y06 Cambridge O Level Physics (5054) 47 Unit 5: Energy and energy sources Recommended prior knowledge Most learners will have some concept of energy in a general industrial or domestic sense but they are less likely to be as precise in their understanding as the subject demands at this level. An elementary experience of the distinctions between the different forms of energy would be useful even at the start of this unit. Context Since energy is one of the fundamental ideas which underpin the whole of this subject, this is another fundamental unit. In the first section, however, one can afford to leave the idea of energy less than properly defined. It does lead into the full and fundamental definition, however, and at that point more care will be needed as the concepts and definitions are used throughout the rest of the course. Outline At first, the fairly gentle topic of energy transformation and energy sources is dealt with. There are few difficult or abstract ideas here and it lends itself to a less mathematical treatment than many other areas. It is desirable, however, to keep the subject as precise as possible and to make sure that learners do not start using terms like power, energy and force interchangeably. It is essential that when energy is properly defined in the second half of this unit, it is done carefully and that its structural importance as a concept is thoroughly emphasised. The terms kinetic and potential energy can be used quantitatively and the definition of work is included. Efficiency and power can be fully defined here, even if they have featured in previous units. The formula, E = mc?, will excite some learners who will believe that they are now real physicists – encourage them. Finally the environmental consequences of power generation will return them to more straightforward and familiar areas. 8(a) List the different forms of energy It is probably best to name and describe the different forms of energy Types of energy: with examples in which each form as they occur in the course rather than to list them in a somewhat www.zephyrus.co.uk/energy1.html occurs. abstract and artificial way all at once. At some point, however, it makes sense to list the energy forms which have been encountered and and to ensure that learners can identify which form of energy is most www.gcse.com/energy/types.htm important in a given change. and Energy cannot be properly defined until work done has been defined (later in this unit), but most learners will have some idea of what energy y.htm means here. 8(b) State the principle of the Consider some particular examples of energy change. Ask Conservation of energy: conservation of energy and apply What energy changes occur in a hydroelectric power station? v0.7 3Y06 Cambridge O Level Physics (5054) 48 this principle to the conversion of astr.gsu.edu/hbase/conser.html energy from one form to another. What energy changes occur when electrical energy is used domestically in the cooker? an electric drill? a mobile telephone and charger? www.physicsclassroom.com/mmedia/ener gy/ie.cfm What energy changes occur in a motor vehicle? When it is going up hill? As it accelerates? Energy transformations: www.physicsclassroom.com/mmedia/ener What energy changes occur in a nuclear power station? gy/pe.html and www.youtube.com/watch?v=cOqSGP6kp mU and www.youtube.com/watch?v=MIqSg4JSJt8 8(d) List renewable and non-Non-renewable energy sources: This can be quite an arid topic if taught conventionally but it does lend renewable energy sources. www.bbc.co.uk/schools/gcsebitesize/geogitself to project work. raphy/energy_resources/energy_rev1.sht 8(e) Describe the processes by which ml Learners might research the whole topic individually or a small group of energy is converted from one learners might research one type of renewable energy and then form to another, including Renewable energy sources: explain their findings to the whole class. reference to: www.renewableenergyworld.com/rea/tech /home (1) chemical/fuel energy (a It is important that learners remember that this is a physics project and regrouping of atoms) they should make clear the origins of the energy source as well as any (2) hydroelectric generation and environmental benefits; e.g. hydrogen is not a source of renewable www.youtube.com/watch?v=kVskMh0Etcs (emphasising the mechanical energy since it has to be generated by some means. What is the energies involved) learner proposing as the source of the energy to generate it? (3) solar energy (nuclei of atoms and www.factmonster.com/ipka/A0907040.htmin the Sun) Learners should understand that renewable energy does not mean (4) nuclear energy l that it can be „used again?, rather that it is being renewed as it is used (5) geothermal energy so that it will „not run out?. (6) wind energy. Emphasise that the Sun is the ultimate source of most energy consumed on Earth but that this is not true of geothermal energy, nuclear energy and tidal energy. V0.7 3Y06 Cambridge O Level Physics (5054) 49 Discuss whether wood is a renewable or non-renewable source of energy. It can be renewed by planting new trees but this is not always done. 8(j) Calculate work done from the Emphasise the difference between doing work and getting tired. A Work done: formula human gets tired supporting a weight at a constant height even though www.physicsclassroom.com/class/energy/ no work is being done. Likewise no work is done against gravity when u5l1aa.cfm work = force × distance moved in a suitcase is moved horizontally. the line of action of the force. and Give many examples including: lifting a load vertically upwards, rolling 8(c) State that kinetic energy is given a barrel up a plank at an angle, removing an electron from an atom, e_46390.html by excited nuclei rearranging themselves after radioactive decay (gamma-and radiation). www.youtube.com/watch?v=XrPEpCr-uCc E = ?mv? k and that gravitational potential Gravitational potential energy: The formula mgh comes from force distance. is given by Doing work is the same as transferring energy and energy is the ability astr.gsu.edu/hbase/gpot.html E = mgh to do work. The two quantities are inextricably intertwined. This is pand true quantitatively and so they have the same unit. and use these equations in www.bbc.co.uk/schools/gcsebitesize/sciecalculations. nce/add_gateway_pre_2011/forces/themeThe formula ?mv? can be deduced from F = ma and a = (v?–u?)/2s. It ridesrev1.shtml is probably better just to state it at this stage. 8(j) Calculate the efficiency of an Kinetic energy: energy conversion using the Mechanical energy is simply the sum of a body?s kinetic and potential efficiency = energy energies. converted to the required astr.gsu.edu/hbase/ke.html form/total energy input. and www.physicsclassroom.com/class/energy/ u5l1c.cfm Mechanical energy: astr.gsu.edu/hbase/ke.html. 8(g) Describe the process of electricity Emphasise that every energy conversion generates some heat which Power station efficiency: generation and draw a block is usually lost to the surroundings. Try to discourage learners from www.bbc.co.uk/schools/g diagram of the process from fuel simply writing “…lost as heat, light and sound”. Few systems waste V0.7 3Y06 Cambridge O Level Physics (5054) 50 input to electricity output. energy as light and those which do lose energy as sound, lose very and little when compared to the quantity lost as heat. It is always better to www.makingthemodernworld.org.uk/learni 8(k) Discuss the efficiency of energy say how the energy is being lost. Energy is lost as heat because of ng_modules/geography/06.TU.06/?sectioconversions in common use, friction between the moving parts. n=6 particularly those giving electrical output. Figures on energy input and output are usually available from a local power station and this may even be a convenient place in the course to arrange a visit. A discussion of power station efficiency might include 8(l) Discuss the usefulness of energy output from a number of energy more efficient systems including combined power and heat (C.P.H.) conversions. 8(m) Calculate the power from the This definition gives a specific meaning to power which is distinct from Work and power: formula energy. Power is always: the rate of change of something measured www.physicsclassroom.com/Class/energy in joules. /U5L1a.html power = work done/time taken. Give examples: the rate of doing work, the rate of losing heat, the rate and of generating energy, etc. www.physicsclassroom.com/class/energy/ u5l1e.cfm 8(f) Explain nuclear fusion and fission These two opposite processes both release energy but emphasise that Energy in fission and fusion: in terms of energy releasing fusion only releases energy for small nuclei and fission for large ones. www.energyquest.ca.gov/story/chapter13.processes. html Quote the accurate masses of the proton, neutron and helium nucleus and show that m < 2m + 2m. Hepn Consider a few specific examples of fission such as: U + ,Ba + Kr + 3 8(h) Discuss the environmental issues Start a class discussion. Groups put forward the merits of building a Environmental issues: associated with power particular sort of power station for their country/community. Learners www.gcse.com/energy/climate_change.htgeneration. tend to concentrate on the negative aspects of power generation: m global-warming, pollution, radioactive discharges and health effects. They should be reminded of the importance of an adequate power and supply. www.succeedingwithscience.com/resourc es/energyandtheenvironment/ V0.7 3Y06 Cambridge O Level Physics (5054) 51 Past paper questions: Nov 12 Paper 21 Q3 Nov 12 Paper 22 Q3 Jun 12 Paper 21 Q2 Nov 11 Paper 21 Q2 Jun 11 Paper 21 Q3 Past question papers available at: V0.7 3Y06 Cambridge O Level Physics (5054) 52 Unit 6: Thermal energy and matter Recommended prior knowledge Learners should have encountered some basic ideas concerning heat and temperature and the difference between them needs to be made clear e.g. a spark has a high temperature but can emit only a little thermal energy whilst the polar sea is cold but the internal energy of all its molecules is large. Many learners will not distinguish between electrical and thermal conduction and will, also, need to be put straight. Learners will need to know terms like insulation and radiation (applied to I.R. radiation). Some elementary kinetic theory is also needed for this unit. Context This unit introduces the topic of thermodynamics – another hugely significant area of physics. Many large industries rely on its being understood. This unit could be fitted into a course almost anywhere since it is, to some extent, independent of many of the concepts on which the other units rely. Energy, however, ought to have been properly defined before it is taught. Heat is often referred to as thermal energy. Outline The early ideas of conduction and convection are fairly easy to explain and to understand and many learners will already be aware of these two energy transmission mechanisms. Radiation is likely to prove harder and it is worth ensuring that learners have a clear understanding of this topic before moving on. The effective insulation of buildings is dealt with and the manner in which a thermometer functions will be introduced here. Learners will meet these phenomena: expansion, boiling, melting and evaporation. The definitions of heat capacity, specific heat capacity and specific latent heat are included in this unit. Classroom organisation and differentiation details: W: whole class; G: group; I: individual 9(a) Describe how to distinguish Basic: Heat transfer: between good and bad There are many simple examples. www.lanly.com/heating.htm conductors of heat. Stir hot tea with plastic, wooden, glass, aluminium, stainless steel and and silver spoons/rods. (I G W) www.mansfieldct.org/schools/mms/staff /hand/convcondrad.htm Poke a fire with, or place in a Bunsen flame, iron, brass and copper rods. (I G W) and www.bbc.co.uk/schools/gcsebitesize/sci Give practical examples: a saucepan should be made from a good ence/aqa_pre_2011/energy/heatrev1.shv0.7 3Y06 Cambridge O Level Physics (5054) 53 conductor whilst its handle is made from a poor one. There are many tml others. (W) Thermal conduction: There are several types of simple equipment which show comparative thermal conduction properties. (I G W) ermal.html and www.youtube.com/watch?v=XbOQCiG HaZE 9(b) Describe, in terms of the Basc: Conduction by molecules: movement of molecules or free Use a model of a solid structure (balls joined by springs) and show that www.schoolphysics.co.uk/age11- electrons, how heat transfer shaking one end leads to vibrations at the other. (W) 14/glance/Heat%20energy/Conduction_occurs in solids. of_heat/index.html In a metal, a vibrating atom can propel electrons a very long distance at high speed. They collide with other atoms far off and set them vibrating. This is a much faster process. (W) Learners can be linked together in a line using their arms and vibrations can be sent along the line. (G W) Compare metallic conduction with kicking a football the entire length of the pitch. (W) 9(c) Describe convection in fluids in Use a Bunsen burner to heat a beaker of water at one side, on the Convection: terms of density changes. bottom. The convection current can be seen using a few tiny crystals of www.bbc.co.uk/schools/gcsebitesize/sci potassium permanganate at the bottom. (G W) ence/aqa_pre_2011/energy/heatrev1.sh tml Special tubes which link back on themselves in a square shape can be used to illustrate convection. (G W) and www.youtube.com/watch?v=6sAFtRQS Challenging: 9XY There is a clear series of events which take place in convection: hot water expands ? its density falls ? it rises ? it pushes away the liquid above it and sucks in the liquid next to it ? a circulation is set up. Illustrate convection with specific examples: , wind V0.7 3Y06 Cambridge O Level Physics (5054) 54 , heat transmitted around a room , the ice box in a refrigerator cools the area below it. (W) 9(d) Describe the process of heat Basic: IR radiation: transfer by radiation. Hot objects emit I.R. radiation (Unit 6). The hotter the object, the more www.gcse.com/energy/radiation.htm radiation it emits. At equilibrium, an object absorbs just as much as it emits. and 9(e) Describe how to distinguish between good and bad emitters www.bbc.co.uk/schools/gcsebitesize/sci and good and bad absorbers of Be careful to distinguish between absorption and emission. (I G W) ence/aqa/heatingandcooling/heatingrev 1.shtml infra-red radiation. Absorption experiment: set up a black can of water and a white can of water in direct sunlight. Determine the temperature rises. Wear a black Absorption/emission: T-shirt and a white one in direct sunlight. What happens? (I G W) astr.gsu.edu/hbase/thermo/absrad.html Emission experiment: set up the two cans filled with boiling water in the shade. Record the temperature drop with time. (I G W) and Examples include: on.html , energy from Sun to Earth , electric fires (not radiators) , thermal imaging. Challenging: Trick question: Why are polar bears white? Answer: Camouflage. 9(f) Describe how heat is transferred Basic: Insulation: to or from buildings and to or from Simple experiments measuring the temperature drop of a can of water, a www.bbc.co.uk/bitesize/standard/physica room. warm piece of metal, or even a thermometer itself, lagged in different s/energy_matters/heat_in_the_home/reways or given a thin black coating from a sooty candle can be used to vision/1/ illustrate the processes. (I G W) 9(g) State and explain the use of important practical methods of heat insulation for buildings. Challenging: and The poor conductivity of air does not itself explain insulation, as most www.school-for-buildings are surrounded by many metres of air. Most heat is transferred champions.com/science/thermal_insulat to or from buildings and rooms by convection in the air. The principle of ion.htm most insulation mechanisms is to suppress convection. This is done by trapping the air. It is then important that air is a poor conductor of heat. V0.7 3Y06 Cambridge O Level Physics (5054) 55 A few insulation techniques are not designed to suppress convection. (W) Why is white a popular colour for houses in hot countries? Consider the day and the night. (I G W) 10(a) Explain how a physical property Basic: Thermometric parameters: which varies with temperature Make it clear that the property chosen must change significantly, www.cartage.org.lb/en/themes/Sciencemay be used for the measurably and always in the same direction (prevents ambiguity). s/Physics/Thermodynamics/AboutTempmeasurement of temperature and erature/Development/Development.htm state examples of such Any property which behaves in this way this will do. properties. Mention: , volume of mercury/ethanol , resistance of platinum , thermoelectric e.m.f. of a thermocouple. (W) 10(b) Explain the need for fixed points Basic: Fixed points: and state what is meant by the Two points are needed to draw a straight line (on a graph) and two fixed www.riverdeep.net/current/2001/11/112ice point and the steam point. points are needed to specify exactly every particular, intermediate point. 601_celsius.jhtml Give some idea of how they are obtained in practice. (W) and Calibrate a thermometer on which no scale has been marked (use at/tep/tempe02_e.html rubber bands or a permanent pen to mark the fixed points), or check a laboratory thermometer. (I G W) Challenging: Emphasise that the ice point is the only temperature at which ice and water can co-exist and the steam point is the only temperature at which water and steam may co-exist – both at standard atmospheric pressure. (W) 10(d) Describe the structure and action Basic: Thermometers: of liquid-in-glass thermometers Let learners see a variety of liquid-in-glass thermometers with different www.bbc.co.uk/bitesize/standard/physic(including clinical) and of a ranges and sensitivities. Get them to explain why one thermometer has s/health_physics/use_of_thermometers/thermocouple thermometer, a greater range than another or why the graduations on one revision/1/ showing an appreciation of its use thermometer are closer than on another. Let them see that the bulbs V0.7 3Y06 Cambridge O Level Physics (5054) 56 for measuring high temperatures have different volumes, the bores are different, the lengths are different Range and sensitivity: and those which vary rapidly. and the liquids might well be different. Will these thermometers be www.physicsclassroom.com/class/ther linear? How were the points marked on the scale? (I G) malP/u18l1b.cfm 10(c) Discuss sensitivity, range and Consider the difficulty of reading a temperature when the thermometer is and linearity of thermometers. in someone?s mouth. How can this be solved? How would the learners design a clinical thermometer – one that maintains its maximum physics/thermometer.html reading? (G W) Thermocouples: Describe and show a thermocouple. (W) www.youtube.com/watch?v=BB5jjW1V 2DI Discuss its advantages and disadvantages. (G W) and Challenging: Will its readings (between 0 ?C and 100 ?C) agree with those on the 2010/11/thermocouple- liquid-in-glass thermometer? thermometer.html Use a thermocouple to observe the cooling of a beaker of hot water. (I G W) 11(a) Describe a rise in temperature of Basic: Kinetic theory: a body in terms of an increase in State the increasing speed of the molecules as the temperature rises as www.school-for- its internal energy (random a fact but try to justify it, e.g. as temperature rises: champions.com/science/matter_kinetic_thermal energy). theory.htm , Brownian motion becomes more violent , chemical reactions speed up and , the speed of sound in gases rises. (W) www.youtube.com/watch?v=_rsqBNhF G1Y: and physics/kinetic-theory/ 11(b) Define the terms heat capacity Basic: Heat capacity: and specific heat capacity. Emphasise that a rise in temperature is a consequence of the transfer of V0.7 3Y06 Cambridge O Level Physics (5054) 57 11(c) Calculate the heat transferred thermal energy. (Cause and effect). Heat and temperature are not the hemistry/Thermodynamics/Calorimetry/ using the formula same thing. (W) Heat_Capacity thermal energy = Heat water in a beaker with an immersion heater or use an electric Specific heat capacity: mass × specific heat capacity × www.bbc.co.uk/schools/gcsebitesize/scikettle. Plot ,T ? t (temperature rise ? time). The initial straight line change in temperature ence/aqa/heatingandcooling/buildingsrereveals that ,T , Q (heat supplied) since Q = Pt. Kettles often have a v3.shtml rated power marked on them. Using this value, determine the specific heat capacity of water. (I G W) and www.youtube.com/watch?v=BclB8UaSChallenging: H4g Emphasise that heat capacity is measured for a particular object whereas specific heat capacity is the property of a substance. Specific heat capacity deals with temperature changes and it unit includes that of temperature. (W) 11(d) Describe melting/solidification Basic: Melting and boiling: and boiling/condensation in terms Cool a test-tube of molten wax (Novadecanol is often used also) and plot www.bbc.co.uk/schools/gcsebitesize/sci of energy transfer without a T? t. Notice the shape of the graph and where the wax becomes solid. ence/ocr_gateway_pre_2011/energy_h change of temperature. Do not melt candle wax or any other inflammable substance with or ome/0_heating_houses2.shtml near a naked flame. (I G W) 11(e) State the meaning of melting and point and boiling point. Measure the temperature of water as it is brought to the boil, and keep measuring it as it boils. (I G W) n12/physics/physics-1/melting-and- boiling Define melting point and boiling point. (W) Challenging: Specific heat capacity is defined for a single phase changing temperature whilst melting and boiling are phase changes occurring at a single temperature. (W) 11(f) Explain the difference between Basic: Evaporation and boiling: boiling and evaporation. Leave various dishes of water in direct sunlight. Record their maximum temperature. Do they ever reach 100 ?C? astr.gsu.edu/hbase/kinetic/vappre.html# Tabulate the differences between the two terms. (I G W) c2 See 12(e) and 12(g) in Unit 9. V0.7 3Y06 Cambridge O Level Physics (5054) 58 11(h) Explain latent heat in terms of Challenging: Vaporisation: molecular behaviour. Explain that melting/boiling involves pulling the molecules apart against an attractive force which is holding the molecules together. (W) astr.gsu.edu/hbase/thermo/phase2.html Basic: and Use a few small balls held together by doubled-sided sticky tape or adhesive strips. Energy is needed (work is done) to separate the balls. 2010/11/latent-heat.html (I) 11(g) Define the terms latent heat and Basic: Latent heat: specific latent heat. Measure the specific latent heat of evaporation of water. Use an electric www.cyberphysics.co.uk/Q&A/KS4/SH kettle whose power rating is known and let the water boil for five or six C/questionsSHC_GCSE.html minutes. Measure the mass of water which escaped. Leaving the lid off 11(i) Calculate heat transferred in a change of state using the formula as it boils should prevent an automatic kettle switching itself off at the and boiling point. (I G W) www.bbc.co.uk/bitesize/standard/physic s/energy_matters/heat_in_the_home/rethermal energy = mass × specific latent heat. Challenging: vision/3/ The latent heat of steam can be used to transfer heat. Consider a “Bain Marie” or a traditional porringer in cooking or a server in a canteen. (W) Specific latent heat: www.s-cool.co.uk/a- level/physics/temperature-and-thermal- properties/revise-it/specific-latent-heat and as-a2/thermal-physics/thermal-energy/ 11(j) Describe qualitatively the thermal Basic: Expansion of solids, liquids and gases: expansion of solids, liquids and Demonstrate specific examples. www.docbrown.info/page03/3_52states.gases. htm Solids: ball and hoop, the bimetallic strip, (I G W) and Liquids: completely fill a flask with coloured water, insert a bung with a www.youtube.com/watch?v=EkQ2886S narrow tube and immerse the flask in hot water. At first the water level xpg in the tube falls as the glass expands but then the level rises. (I G W) Gases: use the flask with the bung and tube empty and invert the equipment and put free end of the tube under water. Bubbles emerge V0.7 3Y06 Cambridge O Level Physics (5054) 59 when the flask is held in warm hands. (I G W) 11(k) Describe the relative order of Challenging: Thermal expansion: magnitude of the expansion of In a liquid-in-glass thermometer, both the liquid and the glass expand. It www.youtube.com/watch?v=EkQ2886Ssolids, liquids and gases. is possible sometimes to see a fall in the liquid level before it rises since xpg the glass expands first. Eventually the liquid expands more and the liquid rises in the tube even though the tube has expanded. (I G W) and www.cyberphysics.co.uk/topics/heat/ex All ideal gases expand at the same rate as each other which is much pansion.htm larger than the rate at which liquids expand. (W) Galilean thermometers work on the same principle. As the temperature rises, the liquid expands more than the solid and so the density of the liquid falls faster. The balls sink. (W) 11(l) List and explain some of the Basic: Expansion causes problems: everyday applications and Ask learners to collect photographs or make drawings of anywhere that www.scienceclarified.com/everyday/Reconsequences of thermal thermal expansion is good or bad and them talk about them to the class al-Life-Physics-Vol-2/Thermal- expansion. (I G W) Expansion-Real-life-applications.html#b All of these are used: the bimetallic strip is the basis of the thermostat, and riveting and fitting metal rims on train wheels, expansion has to be allowed for in tall buildings, overhead power cables, bridges, roads and k/2012/02/useful-applications-of- railway lines. (W) thermal.html The thermal expansion of liquids is the basis of the liquid-in-glass thermometer. (W) Challenging: Fuel is cooled so that more can be put into a racing-car?s tank of a given volume. (W) 11(m) Describe qualitatively the effect of Basic: Charles? Law: a change of temperature on the Demonstrate this effect by trapping air in a capillary tube with an index of www.youtube.com/watch?v=IkRIKGN3ivolume of a gas at constant oil or concentrated sulfuric acid. Put the tube into a beaker of hot water 0k pressure. and as the gas expands, it pushes the index up. If a class set is available learners can plot a graph of the length of the air column and against temperature and extrapolate the graph backwards to zero www.schoolphysics.co.uk/age14- V0.7 3Y06 Cambridge O Level Physics (5054) 60 length. (I G W) 16/Heat%20energy/Gases/text/Charles _law/index.html Past paper questions: Nov 12 Paper 21 Q2 Nov 12 Paper 22 Q4 Nov 12 Paper 22 Q5 Jun 12 Paper 21 Q4 Jun 12 Paper 22 Q3 Past question papers available at: V0.7 3Y06 Cambridge O Level Physics (5054) 61 Unit 7: Magnetism and electric current Recommended prior knowledge Learners are likely to have some elementary ideas concerning magnetism and the Earth?s magnetic field but many will be convinced that all metals are magnetic and will need to be shown otherwise. The first section of this unit is free-standing and could be taught at several stages in the course. It links in well, however, with the second part of the unit which could not properly be taught without a significant amount of current electricity preceding it; this is dealt with in Unit 4. Context The unit deals with magnetism and electromagnetism and it follows on from and extends ideas met in Unit 4. The use of electricity in motors and loudspeakers and the generation of electricity by generators are hugely significant features of the modern world. Physics has changed the human condition enormously and electricity has been a significant factor in this achievement. Outline At the beginning of the unit, the phenomenon of permanent magnetism and magnetic materials is dealt with and this is essential for the understanding of the topics and devices in the second half. Learners will learn about three related magnetic effects. These are the production of a magnetic field by a current, the motor effect and the dynamo effect. Their understanding of these is enhanced by studying particular field patterns, the d.c. motor and the a.c. generator. All these ideas are brought together to explain the operation of a transformer and the use of transformers in power supply systems concludes the unit. Classroom organisation and differentiation details: W: whole class; G: group; I: individual 17(a) State the properties of magnets. Basic: Law of magnetism: Learners should experiment with magnets. Many probably know that like www.zephyrus.co.uk/magneticpoles.ht poles repel and that unlike poles attract. (I G) ml Emphasise “north pole” is an abbreviation for “north-seeking pole”. Use and flat magnets whose flat faces are the poles. To avoid confusion with the www.youtube.com/watch?v=IW7BCTQ geographical locations, some teachers refer only to N-poles and S-poles. DY_g (W) Learners should investigate magnetic behaviour experimentally v0.7 3Y06 Cambridge O Level Physics (5054) 62 themselves. 17(c) State the difference between Basic: Magnetic materials: magnetic, non-magnetic and Learners often think that all metals are magnetic. Try attracting copper, www.zephyrus.co.uk/magneticmaterials magnetised materials. aluminium, brass, nickel (chemical spatulas are often made of nickel), .html carbon, nylon or wood to a magnet. (I G W) Permanent/temporary magnets: 17(f) State the differences between the properties of temporary Given a magnet how would you tell whether a piece of steel was www.miniphysics.com/2012/03/o-level-magnets (e.g. iron) and magnetised or unmagnetised? (I G W) temporary-and-permanent- magnets.html permanent magnets (e.g. steel). Why are permanent magnets and compass needles made of steel? (I G W) Why are the cores of electromagnets made of iron? (I G W) Although iron is often said to be magnetically soft, real iron often retains some residual magnetisation. Find out how stainless steel behaves. (I G W) 17(b) Describe induced magnetism. Basic: Induced magnetism: Pick up chains of iron nails or paper-clips end to end. Remove the www.phy6.org/earthmag/inducemg.htm original magnet. (I) and www.youtube.com/watch?v=SI- x1dWMu54 17(e) Describe the plotting of Basic: Plotting magnetic fields: magnetic field lines with a Plot the field patterns of different arrangements of one or two magnets www.practicalphysics.org/go/Experimen compass. using iron filings (keep the magnet in a plastic bag to keep it clean). t_313.html?topic_id=7&collection_id=41 (I G) and Find the neutral point where appropriate. Also use plotting compasses. www.youtube.com/watch?v=JUZC679C (I G) wKs Learners can become adept at plotting these patterns. Avoid mentioning electric fields here as this causes confusion and if learners use phrases like the charged end of a magnet, be clear to V0.7 3Y06 Cambridge O Level Physics (5054) 63 separate electric terms from magnetic ones. 17(d) Describe electrical methods of Electromagnets: Basic: magnetisation and www.bbc.co.uk/learningzone/clips/electrWrap wire around a brass, iron and steel nail. Pass a current through the demagnetisation. omagnets/289.html wire. Note the different behaviour as you try to pick up paper clips. (I G W) Magnetic tape: 17(g) Describe uses of permanent magnets and electromagnets. is the core of an electromagnet made from? Why? (W) astr.gsu.edu/hbase/audio/tape2.html 17(i) Describe the use of magnetic Uses include: motors, loudspeakers, generators, dynamos, materials in audio/video tapes. Uses of magnets: speedometers, medical scanners, maglev trains, tape-recorders and video www.howmagnetswork.com/uses.html recorders. The phenomenon of electromagnetic induction needs to be taken on trust here as it is not encountered until later in the unit. Learners make their own electromagnet and see how many paper-clips, N, can be picked as the current changes. Plot N ? I. (I G W) Challenging: Note that there are three uses of the term induction in this syllabus: , electrostatic induction , magnetic induction , electromagnetic induction. Learners need to be certain of the differences. (W) Challenging: Magnetised objects can be demagnetised by inserting them into and then removing them slowly from a solenoid carrying a large alternating current. The solenoid should be aligned east-west when doing this. Where possible, the magnetisation can be eliminated by heating to red-heat and allowing to cool in an east-west direction or by hammering the object violently, again with the object lying east-west. (I G W) 17(h) Explain the choice of material Basic: Magnetic Screening: for, and use of, magnetic Notice that this syllabus uses the phrase magnetic screening, other www.exploratorium.edu/snacks/magshiscreening. physicists might use the term magnetic shielding. eld/ V0.7 3Y06 Cambridge O Level Physics (5054) 64 Attach a magnet to the top of a match-box. Remove the drawer and place Uses of magnetic screening: paper-clips at the bottom surface. See how many paper-clips can be www.magneticshield.com/ held. Put into the gap blocks of various materials: polythene, copper, wood, aluminium, brass, steel, iron. How is the number of paper clips and affected? (I G W) www.nuffieldfoundation.org/practical- physics/magnetic-shielding The strength of the magnet (the number of flux lines emerging) is relatively constant. These lines cannot be destroyed or absorbed but they may be channelled away from the protected area; materials which do this are called permeable. All such materials are themselves magnetic. (W) Challenging: Do not confuse with the Faraday cage which screens the protected region from electric fields and is not in this syllabus. Magnetic screening can be used to prevent the magnetic component of a radio-frequency electromagnetic wave from reaching a given location. (W) 17(j) Describe the pattern of the Basic: Fields due to currents: magnetic field due to currents in Use standard equipment to plot the patterns caused by current-carrying , flat coils, solenoids. If possible allow learners to plot the gneticFields/Default.htm and state the effect on the fields with compasses or iron filings. (I G W) magnetic field of changing the and magnitude and direction of the Challenging: . Plot the field pattern caused by a Helmholtz pair of coils. Notice how astr.gsu.edu/hbase/magnetic/magcur.ht uniform it is in the middle. (I G W) ml and www.youtube.com/watch?v=3KkOqVEa 1oI 17(k) Describe applications of the Basic: Relays: magnetic effect of a current in Get learners to use a relay to switch one circuit on and off using another www.technologystudent.com/elec1/relarelays and circuit-breakers. circuit. (I G W) y1.htm Examples include the car ignition system. These ideas can prepare and V0.7 3Y06 Cambridge O Level Physics (5054) 65 learners for circuitry using transistors. www.youtube.com/watch?v=qje8LhZXw O0 Trip switches and relays can be demonstrated in class. (I G W) Circuit breakers: astr.gsu.edu/hbase/electric/bregnd.html 22(a) Describe experiments to show Basic: The motor effect: the force on a current-carrying Possible experiments include: www.bbc.co.uk/schools/gcsebitesize/sciconductor, and on a beam of ence/edexcel_pre_2011/electricityworldcharged particles, in a magnetic Lay an unwound paper-clip on top of two parallel rails (also unwound /thecostofelectricityrev1.shtml field, including the effect of paper-clips) which lie between the poles of a strong magnet (field reversing downwards). Pass a current into one rail and out of the other. This is the and (1) the current catapult effect. (I G W) www.cyberphysics.co.uk/topics/magnet(2) the direction of the field. sm/electro/Motor%20Effect.htm Pass a current through a strip of aluminium foil in a magnetic field. The 22(b) State the relative directions of foil moves. (I G W) and force, field and current. www.youtube.com/watch?v=tE8hQJrA_ Reverse the current and the field both separately and together. (I G W) XY The motor effect is a 3D effect and the relative directions are not easy to Fleming?s left hand rule: describe or memorise. Fleming?s left-hand rule is a useful way of www.s-cool.co.uk/a- remembering it but it is not a law of physics. level/physics/forces-in-magnetic- fields/revise-it/the-motor-effect-and- Challenging: flemings-left-hand-rule Apply these principles to a beam of electrons. Where possible show a fine-beam tube or a Maltese Cross tube. (W) and www.le.ac.uk/se/centres/sci/selfstudy/m Draw the circular field pattern surrounding a straight wire and add the am12.htm uniform, straight field pattern of a permanent magnet. On one side of the wire they reinforce whilst on the other side they cancel. Hence there are and more field lines on the first side and fewer on the other. The lines behave www.youtube.com/watch?v=9Zy0VHBX like stretched rubber bands and so eject the wire in the direction xLU predicted. (W) 17(k) Describe applications of the Basic: Loudspeakers: magnetic effect of a current in Let the learners see dismantled loudspeakers. (G W) loudspeakers. astr.gsu.edu/hbase/audio/spk.html V0.7 3Y06 Cambridge O Level Physics (5054) 66 Hand out sheets showing incomplete or unlabelled diagrams and let the learners complete them. (I G) and www.youtube.com/watch?v=oGrlz6t28X Make a large, cardboard model (~50 cm diameter) to show the shape and E position of the components. Learners can make coils of fine wire (enamel covered), attach them to a cone of paper, place near a bar magnet and when a.c. from a signal generator passes through sound is heard. (W) Challenging: Link in with sound waves (Unit 2) and alternating current (later in this unit). (W) An a.c. produces an alternating force and the diaphragm vibrates. (W) 22(c) Describe the field patterns Basic: Parallel wires: between currents in parallel Pass a current through two parallel strips of aluminium foil – no magnet www.youtube.com/watch?v=43AeuDvconductors and relate these to needed. Like currents attract. Reverse the current in one strip. Unlike Wc0k the forces which exist between currents repel. Consider the field of one strip and its effect on the current the conductors (excluding the in the other. (I G W) and Earth?s field). www.s-cool.co.uk/a- Draw the field patterns for parallel wires carrying currents in the same level/physics/forces-in-magnetic- directions and then in the opposite directions. Notice, in each case, fields/revise-it/force-on-parallel-wires where the two fields cancel out. (I G W) 22(d) Explain how a current-carrying Basic: Torque on coil: coil in a magnetic field www.youtube.com/watch?v=MosMfPI1Illustrate the effect with a large (~50 cm ~50 cm), non-functioning experiences a turning effect and MNA cardboard model. The magnetic poles are painted cardboard boxes. Use that the effect is increased by real, thick wire but paint arrows to show the current and use drinking increasing straws with arrowheads to show the forces on the two sides of the coil. (1) the number of turns on the coil Wind a simple coil and place it between the poles of a magnet. Its plane (2) the current. lies in the field. It rotates through a quarter turn and stops when perpendicular to the field. (G W) 22(e) Discuss how this turning effect Basic: The electric motor: is used in the action of an Use the cardboard model to show that if the current is reversed when the www.bbc.co.uk/schools/gcsebitesize/scielectric motor. coil is perpendicular to the field then it will continue to rotate in the same ence/edexcel_pre_2011/electricityworld V0.7 3Y06 Cambridge O Level Physics (5054) 67 22(f) Describe the action of a split-direction. /thecostofelectricityrev1.shtml ring commutator in a two-pole, single coil motor and the effect Make a “commutator” from aluminium foil and a cardboard tube and fit it to and of winding the coil on to a soft-the model. Use two other lengths of wire to rub against the commutator. www.youtube.com/watch?v=pKAb7GCkiron cylinder. (G W) oWo Explain that a soft-iron core magnifies and concentrates the magnetic field. (W) Make a simple motor from wire, flat magnets, a former on which to wind the coil and show that it can be made to rotate. (I G W) 23(a) Describe an experiment which Basic: Electromagnetic induction: shows that a changing magnetic Insert a bar magnet into a solenoid connected to a sensitive meter (needle ). Withdraw it. Repeat with the other pole java/faraday2/ circuit. and repeat using the other end of the solenoid. (I G W) and 23(b) State the factors affecting the Insert two or three identical magnets taped together. Vary the rate of www.bbc.co.uk/schools/gcsebitesize/sci insertion. (I G W) ence/add_ocr_pre_2011/electric_circuitmagnitude of the induced e.m.f. s/mainsproducedrev1.shtml A coil with more turns may well have a greater resistance. If this is so, it will produce a similar meter reading. Show the dependence on the and number of turns, N, using the same piece of wire wound into more or fewer turns. ?vid=405 Other experiments include: (1) Move a wire up and down between two poles of a magnet. (2) Rotate a copper disc between the two poles and measure the e.m.f. between axle and circumference. In both cases use a sensitive galvanometer. (G W) 23(c) State that the direction of the Challenging: Lenz?s Law: current produced by an induced Consider the only two possible current directions when inserting a magnet : java/lenzlaw/ producing it (Lenz?s Law) and describe how this law may be One attracts the magnet ? larger current ? stronger field ? faster and demonstrated. magnet ? even larger current. Ever larger amounts of energy come from V0.7 3Y06 Cambridge O Level Physics (5054) 68 nowhere. This is impossible. astr.gsu.edu/hbase/electric/farlaw.html The other repels the magnet ? smaller current ? weaker field ? slower and magnet ? even smaller current. A small amount of energy is generated www.youtube.com/watch?v=sPLawCXv by a small initial push. This, of course, is what happens. (W) Kmg This shows that the Lenz Law is an inevitable consequence of the and Principle of the Conservation of Energy. (W) www.youtube.com/watch?v=HNmgE0rJ _xk Challenging: Demonstrate the direction of the current induced by moving a wire up through the gap between two poles of a strong magnet. The directions are given by Fleming?s right-hand rule or by using the left- hand rule and remembering Lenz?s Law. (I G W) 23(d) Describe a simple form of a.c. Basic: The a.c. generator: generator (rotating coil or Use a large cardboard model to show the arrangement of the parts www.animations.physics.unsw.edu.au/jrotating magnet) and the use of (similar to the motor model in 22(e) and (f)). Place small arrows on the w/electricmotors.html#mandg slip rings where needed. coil to show the direction of the current induced. Make a set of slip rings from aluminium foil and some cardboard tubes. (W) and www.youtube.com/watch?v=d_aTC0iK Challenging: O68 Show an old, cut-up a.c. generator or make a model a.c. generator. Rotate it at a constant rate. A c.r.o. displays the output. (W) 23(e) Sketch a graph of voltage Challenging: An a.c. supply: output against time for a simple Connect an a.c. generator to a c.r.o. (Unit 10) and look at the trace. www.bbc.co.uk/schools/gcsebitesize/scia.c. generator. Measure the periodic time and the amplitude. (I G W) ence/add_aqa_pre_2011/electricity/mai nselectrev5.shtml and www.frankswebspace.org.uk/ScienceA ndMaths/physics/physicsGCSE/dcac.ht m 23(f) Describe the structure and Basic; The transformer: principle of operation of a Make a simple electromagnet (an iron nail wound with wire connected to a V0.7 3Y06 Cambridge O Level Physics (5054) 69 simple iron-cored transformer. supply). Insert it into a coil connected to a galvanometer. Withdraw it. astr.gsu.edu/hbase/magnetic/transf.htm Place the electromagnet into the coil and switch off the supply. This is like l withdrawing it. Switch on. Use an a.c. supply (this is like switching it on and off very fast) and replace the galvanometer with a c.r.o. (Unit 10). and (W) ~svoboda/et a/plots/transformer.html Construct a transformer from an iron bar and wind two coils on it. (This is not very efficient). (I G W) Use a transformer kit with a laminated iron core. (I G W) 23(g) State the advantages of high Basic: Power lines: voltage transmission. Use a model power lines demonstration with torch lamps at the beginning www.practicalphysics.org/go/Experimen and end. Transmit at 3 V. Then step up to 12 V, transmit and step down t_352.html to 3 V. (W) Do not use high voltages on bare wire which the teacher or learners can come into contact with. 23(h) Discuss the environmental and Basic: Environmental effects: cost implications of Overhead: cheaper to build, cheaper to maintain, cheaper to inspect, no www.emfs.info/Sources+of+EMFs/Undeunderground power insulation needed, they stay cool, ugly, a hazard for helicopters, hang-rground/ transmission compared to gliders, children with kites. (G W) overhead lines. Underground: the reverse of the above but a hazard for diggers may ignite gas supplies in earthquakes, problems in flooding. (G W) Many other considerations are involved not least the cost. Always make it clear why the cost is more and whether it is the cost of installation or the cost of running the system that is the problem. (G W) Past paper questions: Nov 12 Paper 21 Q7 Jun 12 Paper 21 Q8 Nov 11 Paper 21 Q6 Nov 11 Paper 22 Q5 Nov 11 Paper 22 Q7 V0.7 3Y06 Cambridge O Level Physics (5054) 70 Past question papers available at: V0.7 3Y06 Cambridge O Level Physics (5054) 71 Unit 8: Forces and motion Recommended prior knowledge This unit introduces some of the most basic concepts in mechanics. The learners will, by this stage in the course, be used to dealing with the idea of force but here for the first time its exact definition is presented. Acceleration is a quantity which learners will struggle with, even though they might well have some intuitive conception of what it means. A failure fully to understand it is often betrayed by an inability to deduce or even consistently to use its correct unit. Similarly terminal velocity is a term which many learners will believe they are acquainted with but which few will fully understand at first. Context The ideas here fit in neatly with those of energy but there is not a huge amount of overlap and, as long as the term force has been taken on trust at an early stage, the proper definition can wait until here with few disadvantages. It need hardly be said that these quantities and concepts form the basis of many types of engineering and yet again this branch of the subject is economically and socially very important indeed. Outline The unit begins by distinguishing between scalar and vector quantities and it teaches learners to combine vectors. Kinematics and the definition of acceleration are dealt with by introducing the appropriate graphs. An understanding of the phenomenon of air resistance enables learners to tackle terminal velocity. The importance of the idea of resistive forces, such as friction, should not be overlooked as it explains why things behave so differently from what a simple interpretation of Newton?s Laws might lead one to expect. Newton?s Second and Third Laws of Motion are covered in this unit and the newton is properly defined. The unit concludes with the phenomenon of motion in a circle and the need for a centripetally directed force to enable it to happen. 1(a) Define the terms scalar and Scalars and vectors: Explain that forces cause movement (acceleration) and that an object vector. (b) Determine the resultant of two cancelling and then opposite forces producing a non-zero, resultant and vectors by a graphical method. force. Consider two forces which are perpendicular and add them www.physicsclassroom.com/Class/1DKigraphically. Introduce the parallelogram rule and the triangle of forces. n/U1L1b.html 1(c) List the vectors and scalars from distance, displacement, length, speed, velocity, time, Forces are not the only quantities which behave like this; any quantity acceleration, mass and force. which has direction is a vector: displacement, velocity, acceleration and v0.7 3Y06 Cambridge O Level Physics (5054) 72 2(e)1 Plot and interpret distance-time force. graphs. The distinctions between distance and displacement or between speed Vector addition: and velocity are arbitrary conventions in physics which have to be learnt. They are conveniently illustrated by estimating them for a racing car astr.gsu.edu/hbase/vect.html travelling at uniform speed at various points around a racing track – especially after a whole number of laps. and www.youtube.com/watch?v=bPYLWjcY Consider the distance-time graph and take its gradient. 9wA Emphasise that any quantity which makes sense when followed by a direction word is a vector. Both a force of 3.0 N upwards and a displacement of 0.45 m west make sense; but a temperature of 47 ?C sideways does not. Simple experiments using forces tables or weights hung from strings can verify the rule. Use newtonmeters. Use scale drawings for velocities and displacements. 2(e)2 Plot and interpret speed-time Learners often find rates of anything difficult. Plot graphs of learner?s Acceleration: graphs. height ? time, or volume of water in bath ? time or any quantity with a www.physicsclassroom.com/mmedia/kisingle unit ? time. Talk about metres/year, litres/minute or nema/acceln.cfm 2(c) State what is meant by uniform somethings/second. With a flying start, measure the time for a learner to acceleration and calculate the run or bicycle 10 m, 20 m, 30 m etc. and plot distance ? time graphs. and value of an acceleration using , its velocity is h3.htm increasing. The rate will be measured in (m / s) / s. Consider numerical values. Calculate a. Calculate the gradient of a speed-time graph. 2(h) State that the acceleration of free-and fall for a body near the Earth is Consider the distance-time graph of an accelerating body. www.youtube.com/watch?v=0ROHAAj7 constant and is approximately y00 Run across the classroom accelerating from rest. Then decelerate. 10 m / s?. Freefall: Introduce the unit m / s? and consider objects falling from cliffs; notice www.youtube.com/watch?v=5qh1NDRithat they travel further in each subsequent second. Use 10 m / s? to s58&feature=related calculate the velocities and displacements for falling objects. For a uniformly accelerating object the average velocity = (u+v)/2. and www.youtube.com/watch?v=6MVPUUH zGlk&feature=related V0.7 3Y06 Cambridge O Level Physics (5054) 73 Non-uniform acceleration: Speed-time graphs: www.bbc.co.uk/learningzone/clips/spee d-time-graphs/10673.html and www.bbc.co.uk/schools/gcsebitesize/sci ence/add_gateway_pre_2011/forces/ac celerationrev2.shtml 2(i) Describe qualitatively the motion An object reaching terminal velocity is a good example to consider. Terminal velocity: of bodies with constant weight Emphasise the distinction between a decreasing acceleration and a falling with and without air deceleration (negative acceleration). Consider the motion of a falling astr.gsu.edu/hbase/airfri2.html resistance (including reference to parachutist. Set up a tube containing a viscous liquid and drop ball- terminal velocity). bearings into it. and www.bbc.co.uk/schools/gcsebitesize/sci 2(d) Discuss non-uniform acceleration. Or consider a rocket which accelerates at an increasing rate as its mass ence/add_aqa_pre_2011/forces/forcem decreases. (F = ma is dealt with later.) assact.shtml 2(f) Recognise from the shape of a speed-time graph when a body is Consider the speed-time graph in both cases. (1) at rest Make sure that distance-time and speed-time graphs and their gradients (2) moving with uniform speed (3) moving with uniform are understood. acceleration Set up a large pendulum (l ~ 3 m) and observe its motion when moving (4) moving with non-uniform acceleration. with a large amplitude; try to plot an approximate speed-time graph. 2(g) Calculate the area under a Learners will probably be able to use the formula x = vt in ordinary Area under the graph: speed-time graph to determine situations – when travelling for 3 h at 5 km / h one moves 15 km. Use www.bbc.co.uk/schools/gcsebitesize/scithe distance travelled for motion these ideas in the case of a speed-time graph for a body moving at ence/add_gateway_pre_2011/forces/acwith uniform speed or uniform constant speed. celerationrev2.shtml acceleration. Emphasise that area does not mean cm? of graph paper but area and according to the two axes. This has unit of m/s × s: m. www.physicsclassroom.com/class/1dkin /u1l4e.cfm V0.7 3Y06 Cambridge O Level Physics (5054) 74 3(a) State Newton?s third law. Emphasise that forces always occur in pairs; single forces never exist. The third law: www.physicsclassroom.com/class/newtlThe horse pulls the cart, the cart restrains the horse. aws/u2l4a.cfm Suspend a hook from a support or the ceiling by friction alone. Suspend and a weight from the hook. Gradually increase the weight supported. As www.youtube.com/watch?v=cP0Bb3Wthe hook exerts a larger force on the weight, the weight exerts a larger XJ_k force on the hook which is eventually pulled from its support. and Get two learners to lean against each other back to back at an angle. www.youtube.com/watch?v=D4j5bcaV2As A supports B, so B supports A. Ws Stand a learner on a set of scales. As the weight pushes down on the scales and is recorded, so the scales push upwards on the learner, who does fall to the floor but stays a few centimetres (the thickness of the scales) above it. Emphasise that two third law forces never act on the same body. The forces are always of the form: the force on A due to B and the force on B due to A: F = –FBA AB Two forces acting on the same body may well be equal in size, opposite in direction and of the same nature, but they cannot be a third law pair. Learners are likely to use the formulation: to every action there is an equal and opposite reaction. This is unhelpful. By the terms action and reaction, Newton meant that quantity which we call force. In other words, quantities that we measure in newtons. We tend not to use the term action to mean this anymore and only use the term reaction in this sense rarely. 3(c) Describe the ways in which a A body experiencing no resultant force will have zero acceleration Friction free motion: force may change the motion of a (constant velocity, but not necessarily zero velocity). Consider: ice-www.bbc.co.uk/schools/scienceclips/agbody. hockey pucks, snooker balls, maglev trains, hovercraft and space-craft. es/8_9/friction.shtml 3(b) Describe the effect of balanced The Voyager probes are still travelling in straight lines at huge velocities and and unbalanced forces on a body. V0.7 3Y06 Cambridge O Level Physics (5054) 75 3(d) Do calculations using the long after their engines stopped working. www.fearofphysics.com/Friction/friction.equation html Get the learners to contribute as many appropriate words as possible: force = mass × acceleration. speeding up, slowing down, stopping, changing direction, reversing, F = ma: swerving, lifting and so on. www.dynamicscience.com.au/tester/sol utions/flight/velocity/force.htm Show that acceleration is the consequence of a resultant force. Pull a trolley along a track using a falling weight and a pulley. If possible use and tickertape timers, (or motion sensors and dataloggers) and trolleys to www.youtube.com/watch?v=WzvhuQ5 RWJE show: a , F and a , 1/m. So F = kma but that in SI, k =1; this defines the newton. Examples of zero resultant force acting on a stationary body are numerous. A school resting on its foundations, a book resting on a table, an exhausted athlete lying on a trampoline (here the stretching of the support can be noticed; in the other two cases it is too small to observe). 3(e) Explain the effects of friction on Emphasise that the consequence of a constant, resultant force is a Stopping distances: the motion of a body. constant acceleration not a constant velocity. Emphasise that when www.bbc.co.uk/schools/gcsebitesize/sci cars, trains and aeroplanes are travelling at constant velocity, the ence tractive force is used to cancel frictional forces. 3(f) Discuss the effects of friction on the motion of a vehicle in the and context of tyre surface, road Consider the effect of reducing or increasing friction between the road www.cyberphysics.co.uk/topics/forces/s and vehicle: oil spills and ice on roads or gravelled escape lanes for topping_distance.htm conditions (including skidding), braking force, braking distance, lorries on steep hills. thinking distance and stopping Consider the effect of reduced visibility (night, fog, rain) or the driver?s distance. condition (intoxication, tiredness, lack of concentration). 3(g) Describe qualitatively motion in a Pass a thin piece of string (~50 cm) through a narrow length of glass Centripetal motion: circular path due to a constant tubing. Attach an object (small ball) to one end of the string and a perpendicular force, including laboratory weight to the other end. Hold the tube and set the object astr.gsu.edu/hbase/cf.html electrostatic forces on an electron moving in a circle; a balance is reached when the weight supplies the and in an atom and gravitational correct tension in the string to keep the object moving in a circle. Cut www.phy.ntnu.edu.tw/oldjava/circularMforces on a satellite. (F = mv?/r is the string and observe the object fly off in a tangential direction. Make otion/circular3D_e.html not required.) sure that the object moves in a safe direction with no risk of Electrons: V0.7 3Y06 Cambridge O Level Physics (5054) 76 3(h) Discuss how ideas of circular anyone being injured. A force is needed for circular motion and when www.colorado.edu/physics/2000/wavesmotion are related to the motion it is removed, the object reverts to straight line motion with constant _particles/wavpart2.html of the planets in the solar system. velocity. Consider a motorbike travelling around a curve hitting a patch of spilled oil. The removal of friction allows the motorbike to carry on in a straight line and to hit the outside of the curve. Consider: a bucket of water rotated in a vertical circle, holding on to a roundabout or throwing the hammer in athletics. Relate these ideas to the force needed to keep a moving electron in a circular orbit or a moving satellite in orbit around the Earth. The word centripetal – if used at all – must be used as a direction word (just like downwards). Gravitational and electrostatic attractions are forces of physics which in these cases act in a centripetal direction. Past paper questions: Nov 12 Paper 21 Q1 Jun 12 Paper 21 Q1 Jun 12 Paper 22 Q2 Jun 11 Paper 21 Q2 Nov10 Paper 21 Q2 Past question papers available at: V0.7 3Y06 Cambridge O Level Physics (5054) 77 Unit 9: Pressure and gases Recommended prior knowledge This unit introduces pressure and many learners will have encountered this quantity in one way or another. By this stage in the course, learners will already have met the idea of force but, even if they have not, it can be taken on trust prior to its being properly defined. Gas pressure and the pressure caused by solid objects in contact are not, to all learners, obviously related ideas and it would be useful if some were aware of this connection. Some understanding of the kinetic theory of matter will be necessary in explaining the properties of gases. Context This unit contains various ideas which involve pressure and the properties of gases but which are not, at first sight, obviously related. These ideas are useful in mechanics and thermodynamics but to learners they may well appear to be topics which are not central to the syllabus as a whole. Undermine this impression by emphasising, whenever appropriate, the relationships of the concepts included here to those elsewhere in the course. Outline This unit defines pressure and then applies it to situations involving solids, liquids and gases. Two simple pressure-measuring instruments are described and the operation of hydraulic machines explained. At this stage, Boyle?s Law is introduced and used. This leads to a more thorough look at gases and how the behaviour of their molecules can explain their properties. Evaporation is re-examined in molecular terms at the conclusion of the unit. Classroom organisation and differentiation details: W: whole class; G: group; I: individual 7(a) Define the term pressure in terms Basic; Pressure: of force and area, and do Use an inflating balloon to lift weights. Two square holes of different www.youtube.com/ calculations using the equation sizes are cut in the flat upper surface of a thin wooden box. A large balloon is placed in the box. The sections which were cut out of the box and pressure = force/area. are placed back in the holes. As the balloon inflates, the small wooden platforms rise up lifting weights placed on them. The larger area astr.gsu.edu/hbase/press.html v0.7 3Y06 Cambridge O Level Physics (5054) 78 7(b) Explain how pressure varies with platform can lift a larger weight. (I G W) Simple experiments: force and area in the context of everyday examples. Show the effect of pressure in experiments. Place heavy cones on periments.htm sand, both upright and inverted, or construct a “bed” of nails (~25 cm × ~25 cm) and stand on it carefully. (I G W) and www.youtube.com/watch?v=2VHneRg0 Many simple examples illustrate the significance of pressure: mhI , the ineffectiveness of a blunt knife Examples: , walking on snow in ordinary shoes – use snowshoes , a nail or drawing pin has a large area at one end and a smaller astr.gsu.edu/hbase/kinetic/patm.html one at the other , heavy vehicles on soft ground need large area caterpillar tracks, compare elephants and women in stiletto heels. (I G W) 7(d) Explain quantitatively how the Challenging: Pressure in liquids: pressure beneath a liquid surface Deduce the formula p = hdg by considering the weight of a certain depth changes with depth and density of liquid acting on the base of a tank. astr.gsu.edu/hbase/pflu.html of the liquid in appropriate examples. Consider specific examples: and www.youtube.com/watch?v=ZUfQmjcz2, the increase of pressure with depth (1 atm. /10 m) 7(e) Do calculations using the vg , the pressure divers encounter at 20 m equation for hydrostatic pressure , the pressure at a depth of 10 000 m (the Mindanao trench). and (I G W) www.youtube.com/watch?v=ww5Rynzgp = hdg. pdw Basic: Let water escape out of narrow tubes at different levels in the side of a Pressure in the sea: cylinder of height ~50 cm, filled with water. The lowest jet squirts the www.grc.nasa.gov/WWW/k-furthest. (W) 12/WindTunnel/Activities/fluid_pressure .html Lower a sensitive pressure gauge into water and observe the reading. (I G W) 7(c) Describe how the height of a Basic: Torricelli?s experiment: liquid column may be used to Consider inverting a 1.0 m tube full of mercury into a small mercury bath measure the atmospheric (wear thin plastic gloves to prevent mercury absorption through the pressure. skin). Calculate the pressure at the base of the column of mercury. It Making a barometer: exceeds atmospheric pressure. The mercury flows out of the tube until www.youtube.com/watch?v=GgBE8_Sy the pressure of the mercury equals that of the atmosphere. What QCU V0.7 3Y06 Cambridge O Level Physics (5054) 79 happens as the atmospheric pressure changes? (W) . Describe a manometer and make a simple one to measure the excess pressure of the gas main. (I G W) Measure how hard a learner can blow. A water manometer will need to be ~3.0 m tall for this. (I G W) To make a barometer with water would need plastic tubing of length 10 m; it is what Torricelli did. It can be done. (W) 7(f) Describe the use of a manometer Challenging: Manometer: in the measurement of pressure Pour water into a U-tube. Into one limb pour a less dense liquid. The www.youtube.com/watch?v=5QEAHhXdifference. top levels in the limbs are unequal. This is especially surprising if the Au3M second liquid can mix with water (e.g. ethanol). (W) and 2010/08/gas-pressure.html 7(g) Describe and explain the Basic: Hydraulic brakes or press: transmission of pressure in Make a model hydraulic jack with two vertical syringes of different www.darvill.clara.net/enforcemot/pressuhydraulic systems with particular diameters. The syringes are half-filled with oil and their jets joined with re.htm reference to the hydraulic press tubing (filled with oil – water can be used but forms bubbles of air). and hydraulic brakes on vehicles. Pushing down one piston lifts the other. Use a small weight on the and smaller syringe to lift a greater one on the larger syringe. A small force www.youtube.com/watch?v=ANsFhXhf is being magnified. Compare the distances through which the two Xao weights move. (I G W) Hydraulic brakes: Challenging: www.youtube.com/watch?v=LYetGatz Solids transmit forces, whereas liquids and gases transmit pressures. WjM Hand out incomplete or unlabelled diagrams of these devices and let the learners complete them. (W) 7(h) Describe how a change in volume Basic: Boyle?s Law: of a fixed mass of gas at constant Learners will know that reducing the volume of a gas increases its www.grc.nasa.gov/WWW/K- temperature is caused by a pressure. Place a finger over the end of a bicycle pump; it takes a large 12/airplane/aboyle.html change in pressure applied to the force to compress the gas. (I G W) gas. V0.7 3Y06 Cambridge O Level Physics (5054) 80 7(i) Do calculations using Use a standard piece of equipment to demonstrate Boyle?s Law. (G W) and www.youtube.com/watch?v=J_I8Y- V = pV. Consider examples such as: i4Axc p1122 , bubbles released from sinking ships and , the volume of a free diver?s lungs at ~70 m below sea www.s-cool.co.uk/gcse/physics/forces-level moments-and-pressure/revise-it/forces-, partially inflated meteorological balloons released from and-pressure the earth?s surface. (W) Challenging: Explain the law in molecular terms. In a larger volume the molecular density is lower and so there are fewer collisions with the walls of the vessel per second. The pressure falls. (W) 12(a) State the distinguishing properties Basic: Solids, liquids and gases: of solids, liquids and gases. Learners will be very familiar with these properties. This is a sensible www.youtube.com/watch?v=v12xG80K time to tabulate them. Include: solids transmit forces; liquids and gases cZw transmit pressures. (I G W) and www.youtube.com/watch?v=3qAs1Nt0F jk 12(b) Describe qualitatively the Basic: Brownian motion: molecular structure of solids, Show learners models of solid structures. Balls joined together by www.youtube.com/watch?v=cDcprgWiliquids and gases, relating their springs and balls glued together directly. Use glass beads in a tube with QEY properties to the forces and a vibrating base to simulate the three states. (W) distances between molecules and and to the motion of the molecules. Learners can act out the behaviour of solids, liquids and gases as they www.youtube.com/watch?v=3EHQf3HR behave like molecules themselves. (W) iDc Challenging: and Show the Brownian motion of smoke particles. (W) www.youtube.com/ Calculate or give values for the separation of molecules in liquids and solids. (W) Calculate the separation of molecules in air at room temperature. (W) V0.7 3Y06 Cambridge O Level Physics (5054) 81 Note that Brownian motion is the motion of the suspended particles not the motion of the atoms or molecules. 12(c) Describe the relationship between Basic: Moving molecules: the motion of molecules and State as a fact that molecules travel faster at higher temperatures. (W) Molecules in solids vibrate but in gases they travel in straight lines between collisions. (W) Challenging: Ask learners to explain why: , the speed of sound in air increases with temperature , the pressure of a trapped gas rises with temperature. Take a hollow, copper sphere with a pressure gauge attached. The pressure increases with its temperature. (I G W) 12(d) Explain the pressure of a gas in Basic: Pressure and temperature: terms of the motion of its Explain that the collisions of extremely tiny molecules travelling at very detected on a macroscopic scale as pressure. (W) and A football can be kept in the air by constantly punching it from below. astr.gsu.edu/hbase/kinetic/idegas.html Many tiny impacts cause a single force. (W) Balloons burst as a party progresses, it gets hotter in the room and the pressure in the balloons rises. (W) Explain that gas cylinders explode in fires. (W) 12(e) Describe evaporation in terms of Basic; Evaporation: the escape of more energetic The faster molecules escape and so the liquid left behind is cooler. (W) from the surface of a astr.gsu.edu/hbase/kinetic/vappre.html liquid. Place a glass beaker or a copper can on another one which is upside down. Put a small amount of water between them. In the top vessel and pour a small amount of a volatile liquid. Force air rapidly through the www.bbc.co.uk/schools/gcsebitesize/sci12(g) Explain that evaporation causes cooling. liquid so that it evaporates quickly. The water freezes and the lower ence/aqa/heatingandcooling/heatingrev vessel can be lifted up with the upper one. (G W) 5.shtml V0.7 3Y06 Cambridge O Level Physics (5054) 82 Cooling by evaporation: and www.youtube.com/watch?v=G0nWby2f, refrigerators 0ok , perspiration , panting dogs Refrigerators: , wiping ether on an arm before an injection , wrapping butter or ice cream in wet paper to keep it cool. 12(f) Describe how temperature, Basic: Rate of evaporation: surface area and draught over a Carry out some experiments to determine these effects. Use a volatile www.vtaide.com/png/evaporation.htm surface influence evaporation. liquid or use water over several days. (I G W) and How is the shape of a cooking pan determined by what is being cooked? www.youtube.com/watch?v=1AfkJ5KB3 4Y Why does an evaporating dish have a large surface area? (W) Past paper questions: Jun 12 Paper 21 Q3 Jun 12 Paper 22 Q4 Nov 11 Paper 22 Q3 Jun 11 Paper 21 Q4 Jun 11 Paper 22 Q1 Past question papers available at: V0.7 3Y06 Cambridge O Level Physics (5054) 83 Unit 10: Practical electricity Recommended prior knowledge Learners tackling this unit ought to be acquainted with the concept of energy from Unit 5, the basic ideas of current electricity in Unit 4, electromagnetism in Unit 7. This unit ought to be taught near the end of the course. Learners are quite likely to have been aware of the installation of mains electricity or the rewiring of a house but may not be very familiar with the physics which lies behind much of what they have seen. Similarly, the use of the c.r.o. in medical establishments will be familiar but they are unlikely to know how it works. Context This unit applies the rather theoretical aspects of electricity, which have already been dealt with, to more practical circumstances which learners will be quite familiar with. The supply of electricity to homes, offices and industry is a major convenience of the modern world and the electricity supply industry is important in every country in the world. The use and operation of the c.r.o. leads on to some electronic devices and circuits. These are the very foundation of both the electronics industry and the information revolution for which the use of computers and modern communications have been essential. Outline The unit begins with some of the uses of electrical energy on a domestic scale. The formula for power can be used to calculate the rating for the fuse which a particular appliance requires; circuit breakers are dealt with here. The mechanics of charging for electricity is explained and so is the wiring of plugs and the dangers posed by selected electrical hazards. The cathode-ray oscilloscope is described in some detail. Potential dividers, capacitors and reed relays are explained and then used in certain electronic circuits. The last section describes logic gates, transistors, bistable circuits and astable circuits, which are an optional part of the course and may only be of interest to some teachers or learners. Classroom organisation and differentiation details: W: whole class; G: group; I: individual 21(a) Describe the use of electricity in Basic: Uses of electricity: heating, lighting and motors. Emphasise that the overwhelming majority of electrical energy is used in www.youtube.com/watch?v=eUoviiylEm this way. Consider industrial and domestic uses: kettles, furnaces, Q cookers, street lights, table lights, theatre lights, illuminated signs, lighting in greenhouses and zoos, drills, lifts, food-mixers, saw-mills. Consider less obvious and mixed examples: refrigerators, washing v0.7 3Y06 Cambridge O Level Physics (5054) 84 machines and so on. Learners can make their own list and report to the class on the Physics principles by looking around their home or neighbourhood. (I G W) Can these operate on an a.c. supply? (W) Are there other uses of electricity – charging batteries, operating electronics? (I G W) Can these use an a.c. supply? (W) 21(b) Do calculations using the Basic: Electrical power: equation Consider: energy = voltage × charge (Unit 4) and divide both sides by www.kpsec.freeuk.com/power.htm time. The definition: V = P/I is just as satisfactory as the more power = voltage × current, and traditional: V = E/Q and the volt may be taken as the watt/ampere. In www.bbc.co.uk/schools/gcsebitesize/ some ways these definitions are superior as learners are more likely to and be familiar with current than with charge. (W) energy = Since E = Pt so E = VIt. voltage × current × time. 21(e) Explain the use of fuses and Basic: Fuses and circuit breakers: circuit breakers and fuse ratings Produce in class some domestic devices: kettle, drills, radios. Read the is required? Consider car headlamps (12 V) and rechargeable and appliances. (I G W) www.gcsescience.com/pme9.htm Buy a reel of low rating fuse wire (~2A) and allow learners to see it blow or measure how the fusing current depends on the length of fuse wire. (I G W) Challenging: Consider R.C.C.B.s (residual current circuit breakers) 21(c) Calculate the cost of using Basic: Electricity bills: electrical appliances where the Learners realise that the cost of electricity is likely to depend on the www.gcse.com/energy/kWh5.htm energy unit is the kWh. power of the device and the time for which it is used. Hence it depends on P × t. Electricity suppliers tend to use the kW h but emphasise that and V0.7 3Y06 Cambridge O Level Physics (5054) 85 this is a special non-SI unit which equals 3.6 MJ. (G W) www.bbc.co.uk/schools/gcsebitesize/ Show learners an electricity meter and read it. Explain that it keeps a running tally of the energy used. (W) Allow learners to heat up water electrically, measuring power and time, and then calculate the cost of heating up a cup of coffee or tea or a swimming-pool. (I G W) Show learners an actual and recent bill and explain how the final cost is calculated. (I G W) Challenging: Are there any standing charges? Is there any cheap rate electricity at night? Are there any taxes? 21(g) State the meaning of the terms Mains wiring: Basic: live, neutral and earth. www.frankswebspace.org.uk/ScienceAExplain that the earth wire is a safety feature; the device can function ndMaths without it although it is not safe to let it do so. It is the live and neutral 21(f) Explain the need for earthing wires which constitute the circuit. (W) metal cases and for double Earthing: www.bbc.co.uk/schools/ insulation. Challenging: Emphasise that earthing (the term grounding in used in some places but and 21(i) Explain why switches, fuses and it is not used in this syllabus) operates in conjunction with the fuse; a live www.bbc.co.uk/schools/gcsebitesize/s circuit breakers are wired into the metal case connected to earth is not safe until the large earth current live conductor. drawn through the live blows the fuse. (W) Double insulation: (W) Some devices have a plastic “earth” pin. This operates the safety shield on the socket. (W) The live wire is the one whose voltage varies and this is responsible for the current. The neutral wire (~0 V) completes the circuit. (W) This is why it is the live connection must be broken to make a device V0.7 3Y06 Cambridge O Level Physics (5054) 86 safe. (W) 21(h) Describe how to wire a mains Basic: Electrical safety: plug safely. Candidates will not Allow the learners to wire plugs. (Keep a special set for the learners www.youtube.com/watch?v=- be expected to show knowledge with a screw drilled through it so that it cannot be inserted into a lddGWFBbWI. of the colours of the wires used in socket. This prevents a learner who has wired the plug incorrectly a mains supply. from inserting it into a socket.) (I G W) 21(d) State the hazards of damaged Draw attention to the dangers of frayed wires and cut insulation. Explain that domestic water is quite a good conductor. Do not trail leads under insulation, overheating of cables and damp conditions. carpets. (W) 24(a) State that electrons are emitted Basic: Thermionic emission: by a hot metal filament. State this as a fact. It can be shown by thermionic diodes connected to www.matter.org.uk/tem/electron_gun/el sensitive galvanometers – if available. Or in the fine beam tube the low ectron_gun_simulation.htm 24(b) Explain that to cause a pressure hydrogen indicates the path taken by the emitted electrons.(W) and continuous flow of emitted electrons requires (1) high Challenging: www.youtube.com/watch?v=pw9c- positive potential and (2) very low The path of an electron beam in an electric field can be shown by X6JCdI appropriate thermionic tubes if available but emphasise that the path of gas pressure. the electrons will not be circular in a uniform electric field. The positive Thermionic diodes: plate attracts the negative electrons into a (parabolic) path. (W) www.nationmaster.com/encyclopedia/T24(c)1 Describe the deflection of an hermionic-valve electron beam by electric fields. and www.st- andrews.ac.uk/~jcgl/Scots_Guide/audio /part9/page1.html Electric field deflection: ~duffy/PY106/Elec tricfield.html 24(c)2 Describe the deflection of an Challenging: Magnetic field deflection: electron beam by magnetic fields. The magnetic deflection is in accordance with Fleming?s left-hand rule, www.regentsprep.org/Regents/physics/ bearing in mind that electrons are negatively charged. Emphasise that a phys03/cdeflecte/default.htm uniform magnetic field can deflect an electron beam into a circular path whereas a uniform electric field cannot. (W) V0.7 3Y06 Cambridge O Level Physics (5054) 87 Electrons carry negative charge in the direction of travel which is Negative electrons: equivalent to taking positive charge in the opposite direction. (W) www.kpsec.freeuk.com/electron.htm 24(d) State that the flow of electrons Challenging: Electron current: (electron current) is from negative Compare receiving electrons with receiving a bill; a bill is negative to positive and is in the opposite money and receiving one is a financial loss. (W) . direction to conventional current. 24(e) Describe in outline the basic Basic: C.R.O: structure and action of a cathode-Show the learners a dismantled, old c.r.o. if available. Emphasise that www.nuffieldfoundation.org/practical- ray oscilloscope (c.r.o.) (detailed two pairs of parallel, charged plates deflect the electron beam. (W) physics/using-cro-show-rectification- circuits are not required). diode Emphasise that the left to right motion is controlled by an internal circuit 24(f) Describe the use of a cathode-ray whilst the up and down motion of the beam is controlled by the externally and applied voltage. (W) www.youtube.com/watch?v=0tPEoRSXoscilloscope to display waveforms and to measure p.d.?s and short UlY intervals of time (detailed circuits Use a c.r.o. to display different waveforms from a signal generator. A medical c.r.o. must have a voltage input. There must be an electrical C.R.O. settings: are not required). transducer in a heart monitor. Explain how time intervals can be www.kpsec.freeuk.com/cro.htm obtained from distances measured across the screen and the timebase . setting. Learners will need to practice with specific values. (W) Challenging: The speed of sound in a short, metal rod or even air can be obtained by using a c.r.o. to measure the small time interval. (G W) 24(g) Explain how the values of Basic: Resistor colour code: resistors are chosen according to This just has to be explained but point out that the colours are almost but www.uoguelph.ca/~antoon/gadgets/resi a colour code and why widely not quite the traditional seven colours of the rainbow which learners are stors/resistor.htm different values are needed in likely to know. (I G W) different types of circuit. Make a set of resistors on cards and allow learners to read their values. 24(h) Discuss the need to choose (I G W) components with suitable power Give examples of using different values for different purposes but ratings. remember that the resistance and e.m.f. determines the current. This, in turn, determines the power generated within the resistor. (W) V0.7 3Y06 Cambridge O Level Physics (5054) 88 Challenging: Doubling the length and the cross-sectional area of a resistor keeps its resistance constant but both the mass to be heated and its surface area will be larger. It stays cooler. (W) 24(i) Describe the action of thermistors Basic/challenging: Thermistors and LDRs: and light-dependent resistors and State these behaviours as a fact but emphasise that both the heat in www.bbc.co.uk/schools/gcsebitesize/s explain their use as input sensors (NTC) thermistors and the light in LDR.s are used to free electrons from (thermistors will be assumed to the structure which in turn reduces the resistance. It helps learners to and be of the negative temperature remember how the resistance changes. PTC thermistors behave coefficient type). differently and are not in this syllabus. (W) physics/non-ohmic-devices/ Set up a circuit and show that the total p.d. across two unequal resistors Thermistors: 24(j) Describe the action of a variable potential divider (potentiometer). is unequally divided. (The mouse ends up with the mouse?s share; the www.youtube.com/watch?v=FGt_mAWt lion takes the lion?s share.) (I G) V1Q Use a variable resistor as one of the resistors and adjust it. What LDRs: happens to the voltage of the middle point? (I G W) www.youtube.com/watch?v=Nlkjito8yE A Use a switch, a thermistor and an LDR instead of the variable resistor. (I G W) Try to avoid using a variable resistor on its own as a potential divider until the idea is properly understood. When it is used the resistance of one end increases whilst that of the other end becomes smaller. This is confusing at first. 24(k) Describe the action of a capacitor Challenging: Capacitors: as a charge store and explain its Demonstrate it. Charge up a capacitor in one circuit and then discharge www.kpsec.freeuk.com/components/cause in time-delay circuits. it through a coulombmeter in another circuit. It emphasises the point if pac.htm the two circuits are physically separate and the capacitor has to be physically moved across the room. Then use a single circuit with a Time delay circuits: single-pole double-throw switch. If a coulombmeter is unavailable use www.bbc.co.uk/schools/gcsebitesize/de an LED and a large capacitor; try to get a small flash. (I G W) sign/systemscontrol/pneumaticsrev4.sht ml Put a capacitor (~1 ,F) in series with a resistor (~5 M,) and connect to a d.c. supply (~6 V). Measure the p.d. across the capacitor with a high V0.7 3Y06 Cambridge O Level Physics (5054) 89 resistance voltmeter or c.r.o. and see how quickly the voltage reaches a and www.youtube.com/watch?v=LyKFc5Wlfgiven value (say 4 V). Repeat with a 10 M, resistor. Compare the y0 times. (G W) 24(l) Describe and explain the action of Challenging: Reed switch: reed relays in switching circuits. Use a reed switch to switch on a circuit. Operate the reed switch with a www.eleinmec.com/article.asp?23 bar magnet. Operate it with a clearly separate solenoid. See how close the solenoid has to be to the reed switch before the current in the Reed relay: solenoid will operate the reed switch. (W) www.cougarelectronics.com/relays/reed relays.htm Emphasise that a reed relay is a reed switch with its own built-in solenoid. Show one being used. Use a d.c. circuit containing the and solenoid to operate a low voltage a.c. motor. Emphasise the presence www.youtube.com/watch?v=L9eiQOhT of two distinct circuits which are only linked magnetically. (W) 1fU Use circuits with switches, thermistors or LDRs in series with the solenoid of the reed relay. (I G W) A reed switch could be used to switch on a light when a door is opened or closed. The magnet is fixed to the door. (W) 24(m) Describe and explain circuits Basic: operating as light-sensitive Set up a circuit containing either an LDR or a thermistor and show that switches and temperature the current rises as the light intensity or temperature rises. With a reed operated alarms (using a reed relay in the circuit, a point is reached where the current closes the switch relays or other circuits). inside the reed relay. (I G W) This switch can be in an electrically different circuit that contains a bell or buzzer that rings when the circuit is closed – that is when a certain level of light intensity or temperature is reached. (I G W) 25(a) Describe the action of a bipolar Challenging: Transistor switching circuits: npn transistor as an electrically Set up a transistor switching circuit. E.g. use an LDR/resistor potential operated switch and explain its divider to control the base current and use the collector current to power astr.gsu.edu/hbase/electronic/transwitcuse in switching circuits. a lamp. Emphasise that the transistor is being used as a switch in one h.html circuit powered by the current in the other – just like the reed relay. (I G W) V0.7 3Y06 Cambridge O Level Physics (5054) 90 25(b) State in words and in truth table Basic: Logic gates: form, the action of the following Model AND and OR gate behaviour using switches in series or parallel www.kpsec.freeuk.com/gates.htm logic gates, AND, OR, NAND, in one circuit to operate a reed relay in a second circuit (which includes a NOR, and NOT (inverter). lamp). Emphasise that the second circuit has its own power supply as and do all logic gates. (I G W) www.youtube.com/watch?v=flO8wARV 25(c) State the symbols for the logic DY4 gates listed above (American Model NOT, NAND and NOR gate behaviour by using the reed relay to switch off the second circuit. Emphasise that when the first circuit is ANSI Y 32. 14 symbols will be used). switched off the second is powered by its own supply; likewise when the input to a NOT gate is 0, the logic gate?s own power supply produces the output voltage. (I G W) Challenging: Compare with logic gate circuits and emphasise that a logic gate has its own power supply. A NOT gate does not magically turn 0 V (0) into say 6 V (1). (W) It is worth setting up a few logic gate circuits and explaining how they work: Use a NOT gate and an LDR to switch on a light when it is dark. (W) Use an AND gate to switch on a heater when it is cold and dark. (W) 25(d) Describe the use of a bistable Challenging: Bistable circuits: circuit. Set up a bistable circuit with two NAND gates (or a transistor bistable www.sphaera.co.uk/bistable.htm circuit). Put an LED at one output and a buzzer at the other. Use push 25(e) Discuss the fact that bistable switches. Observe that one switch switches the buzzer on and the LED and off, whilst the other has the reverse effect. (I G W) www.youtube.com/watch?v=0tR5nwfEcircuits exhibit the property of memory. Nb4 Such a circuit can be used as a burglar alarm or an emergency off switch for an escalator. The switch to turn it back on it located elsewhere; the public may only switch it off. (W) Explain that the circuit “can remember” which switch was most recently operated. (W) 25(f) Describe the use of an astable Challenging: Astable circuit: circuit (pulse generator) Set up an astable circuit with NOR gates and capacitors (or a transistor www.bbc.co.uk/schools/gcsebitesize/de V0.7 3Y06 Cambridge O Level Physics (5054) 91 25(g) Describe how the frequency of an astable circuit). Connect the output to a buzzer or an LED. Observe the sign/electronics/integratedrev2.shtml astable circuit is related to the pulsating sound or the flashing light. Vary the value of the resistors and values of the resistive and observe the effect on the pulsing frequency. Vary the value of the and capacitative components. capacitors and repeat the observation. Check for inverse proportionality www.youtube.com/watch?v=tJMN5CR6 in each case. (I G W) aPw Past paper questions: Nov 12 Paper 22 Q7 Nov 11 Paper 21 Q7 Jun 11 Paper 22 Q6 Nov10 Paper 21 Q7 Nov10 Paper 22 Q5 Past question papers available at: ? Cambridge International Examinations 2013 V0.7 3Y06 Cambridge O Level Physics (5054) 92