Answers to questions in the Student Book - Hodder Plus Home

GCSE Physics for CCEA second editionIn-text questions1. a) average speed = total distance ÷ total time= 800 ÷ 40s= 20m/sb) Car may be overtaking or braking.2. a) distance = speed x time= 10m/s x 9s= 90mChapter 1 Motionb) time = distance/speed= 220m ÷ 10 m/s= 22s3. a) Displacement is distance in a given direction i.e., it is a vector quantity.b) Velocity is speed in a given direction i.e., it is a vector quantity.4. a) Runner: average speed = 400m ÷ 44s= 9.09 m/sb) Car: average speed = 175 miles ÷ 3 hour= 5 miles per hourc) Shuttle: average speed = 43 750 000m ÷ 2.5 x 60 x 60s= 4860 m/s5. a) An acceleration of 3m/s 2 means that the train’s velocity increases by 3m/s in each and everysubsequent second.b) The velocity of the bus decreases by 2m/s in each and every subsequent second.6. acceleration = change in velocity/time= (30 – 3) m/s ÷ 8s= 27 ÷ 8= 3.375 m/s 27. u = 25 m/s, v = 0 m/s (comes to a halt), t = 5 s, a = ?v - u 0 - 25 - 25a = -5m/s 2 or deceleration = 5m/s 2t 5 58. a) u = 0 m/s, v = ?, t = 5 s, a = 4 m/s 2v - u v - 0a 4 v = 20m/st 5b) u = 28 m/s, v = ?, t = 8 s, a = 4 m/s 2v = u + at= 28 + (4 x 8)= 28 + 32= 60 m/s1

GCSE Physics for CCEA second edition9.10. a) & b)c) i) Paulii) Paul takes 3.5s, Jim takes 5.5s.iii) 3m.iv) No, gradient changes after 6s.v) Average speed = 14m ÷ 7s = 2m/s.11. Speed increases then becomes steady. Speed is not zero at time t = 0s.2

GCSE Physics for CCEA second edition12. a) Acceleration = gradient= 25 ÷ 5= 5 m/s 2b) total displacement = area of triangle + area of rectangle= (125 ÷ 2 ) + (25 x 10)= 312.5m13. a) i) OA = Uniform accelerationii) AB = Constant velocityiii) BC = Uniform decelerationb) i) Acceleration = gradient = 5m/s ÷ 2s = 2.5m/s 2ii) total distance = area of triangle + area of rectangle + area of triangle= 5m + 5m + 10m= 20miii) average speed = total distance travelled ÷ time taken= 20m ÷ 7s= 2.86m/s14. u = 20m/s, v = ?, t = 10s, a = 3 m/s 2v = u + at= 20 + (3 x 10)= 20 + 30= 50 m/s15. u = 0m/s, a = 0.3m/s 2 , t = 10s, s = ?v = u + at= 0 + 10 x 0.3= 3m/ss = ut + ½ at 2= 0 + ½ x 0.3 x 10 2= 0.3 x 50= 15m16. u = 20m/s, v = 0, a = -10m/s 2 , t = ?, s = ?v = u + at0 = 20 – (10 x t)10t = 20t = 25 ss = ut + ½ at 2= (20 x 2) – (½ x 10 x 2 2 )= 40 - 20= 20m17. u = 0m/s, v = ?, a = 10 m/s 2 , t = 3s, s = ?a) v = u + atv = 0 + 10 x 3v = 30m/s3

GCSE Physics for CCEA second editionb) average speed = (30 + 0) ÷ 2= 15m/sc) s = ut + ½ at 2= 0 + ½ x 10 x 3 2= 45 m18. s = 500m, u = 0m/s, v = ?, a = 10 m/s 2 , t = ?a) v 2 = u 2 + 2as= 2 x 10 x 500= 10 000v = 100m/sb) v = u + at100 = 0 + 10t10t = 100t = 10s19. u = 50m/s, v= 0, a = -10m/s 2 , t = ?, s = ?a) v = u + at0 = 50 – (10 x t)10t = 50t = 5sb) s = ut + ½ at 2= (50 x 5)-(½x10x25)= 250 – 125= 125m20. a) u = 0 m/s, v = ?, a = 3 m/s 2 , t = 5sv = u + at= 0 + 3 x 5= 15m/sb) u = 15, v = 0, t = ?, a = -0.5v = u + at0 = 15 – (0.5 x t)0.5t = 15t = 30sarea of triangle = ½ x b x h= ½ x 35 x 15= 262.5mc)4

GCSE Physics for CCEA second editionExam questions (pages 11–12)1. a) distance = 3km = 3000m, time = 5 mins = 300s, average speed = ?total distance 3000maveragespeed = = 10m/s(6 marks)total time 300 sb) i) acceleration = gradient = 14m/s ÷ 20s = 0.85 m/s 2 (5 marks)ii) RF = m x a = 1500kg x 0.85m/s = 1275NRF = driving force – dragdrag = 3000 – 1275 = 1725N(7 marks)iii) Distance travelled from 80s to 200s is the area of the trapezium:= ½ (a + b) x h= ½ (120 + 80) x 20= 100 x 20= 2000m (6 marks)c) i) Constant velocityii) Decelerationiii) Stationary(3 marks)d) mass = 1500kg, velocity = 14m/s, momentum = ?momentum = mass x velocity= 1500kg x 14m/s= 21 000kgm/s (5 marks)2. a) mass = 10 000kg, g = 10m/s 2 , weight = ?weight = mass x g= 10 000kg x 10m/s 2= 100 000N (2 marks)b) 100 000N (1 mark)c) area = 20m x 5m = 100m 2 , upward force = 100 000N, pressure =?force 100 000 Npressure = 1000 Pa (4 marks)2area 100 md) Arrow to the right. (1 mark)e) RF = 20000 – 15000 = 5000N, mass = 10000kg, acceleration = ?RF = m x a5000 = 10000 x a5000a = 0.5 m/s 2 (4 marks)10 0003. a) The graph does not go below time axis. (1 mark)b) acceleration = gradient = 10m/s ÷ 50s = 0.2m/s 2 (3 marks)c) t = 100s (1 mark)d) i) Stage BC = area of rectangle = 50 x 10 = 500m (2 marks)5

GCSE Physics for CCEA second editionii) Stage CD = area of triangle = ½ x b x h = ½ 125 x 10 = 625 m(3 marks)total distancee) averagespeed =total time250 500 625= 6.11 m/s (3 marks)225f) work done = force x distance = 5000N x 500m = 2500 000J (3 marks)4. a) i) speed = gradient = 14m ÷ 7s = 2m/s (2 marks)ii)(2 marks)b) i) potential energy = mass x g x height320 000J = 80 kg x 10 m/s 2 x heightheight = 320 000 ÷ 800 = 400m(3 marks)ii) kinetic energy = ½ x m x v 2= ½ x 80 x 14 2= 7840J (3 marks)6

GCSE Physics for CCEA second editionIn-text questionsChapter 2 Forces1. a) No acceleration means balanced forces, so there must be a backwards force of 40N acting onbicycle and rider; friction and air resistance.b) RF = 70 – 40 = 30N, m = 90kg, a = ?RF = m x a30 = 90 x aa = 30 ÷ 90 = 0.33m/s 22. m = 1200 kg, a = 2 m/s 2 , RF = (3000 – frictional force)RF = m x a3000 – frictional force = 1200 x 23000 – frictional force = 24003000 – 2400 = frictional force600 = frictional forceor frictional force = 600N3. a) Forwards.b) Consider horizontal forces only. RF = (2000 – 400) = 1600N, m = 800kg, a = ?RF = m x a1600 = 800 x aa = 1600 ÷ 800 = 2m/s 24. a) weight = mass x acceleration due to gravity= 2000 kg x 10 m/s 2= 20000Nb) Consider vertical forces. RF = (25000 – 20000) = 5000N, m = 2000kg, a = ?RF = m x a5000 = 2000 x aa = 5000 ÷ 2000 = 2.5m/s 25. 300N forward thrust. Frictional force due to water must also be 300N backwards, if it travels atconstant speed. RF = (? - 300), m = 500kg, a = 2 m/s 2RF = m x a(? -300) = 500 x 2(? -300) = 1000? = 1000 + 300= 1300N6. RF = (? - 400) N, m = 1200kg, a = 3m/s 2RF = m x a(? -400) = 1200 x 3(? -400) = 3600? = 3600 + 400= 4000N7. a) u = 24m/s, v = 0m/s (brings to rest), t = 8s, a = ?7

GCSE Physics for CCEA second editionv - ua t0 - 248 24 = -3m/s 2 or deceleration = 3m/s8b) RF = ?, a = 3 m/s, m = 1200 kgRF = m x a= 1200 x 3= 3600NNB: No need to substitute a = -3 m/s into formula, as we are only asked for the size of theunbalanced force!8. a) Forces acting on girl must be balanced i.e., the backwards frictional force must also be 120Nif the girl is travelling at a steady speed.b) RF = 300 – 120 = 180N, m = 60kg, a = ?RF = m x a180 = 60 x aa = 180 ÷ 60 = 3m/s 29. a) u = 50m/s, v = 0m/s, t = 5s, a = ?v - u 0 - 50a = -10m/s 2t 5b) a = 10 m/s 2 , m = ?, RF = 18000NRF = m x a18000 = m x 10m = 18000 ÷ 10 = 1800kg10. a) u = 20m/s, v = 0m/s, t = 0.1s, a = ?v - u 0 - 20a = -200m/s 2 or deceleration = 200m/s 2t 0.1b) F = ?, m = 1000kg, a = 200m/s 2F = m x a= 1000 x 200= 200000N11. a) 30km/hr = 30000m in 3600 seconds = 8.33m/sb) u = 8.33m/s, v = 0m/s, t = 0.03s, a = ?v - u 0 - 8.33a = -277.7m/s 2t 0.03c) a = 277.7m/s 2 , m = 70kg, RF = ?RF = m x a= 70 x 277.7= 19 444 N12. Weight is measured in Newtons, so Julie should have said ‘My weight is 350 N’ or ‘My mass is35 kg’.13. As soon as it enters the oil, the ball will decelerate until its weight is equal to the viscous drag.Then the ball will fall with constant (terminal) velocity.8

GCSE Physics for CCEA second edition14. There is no atmosphere on the Moon. The hammer and feather will experience no drag forces, sothey will both accelerate at 1.6 m/s 2 and hit the surface of the moon simultaneously.15. When the parachute opens, the vertical drag force increases, decreasing the velocity of theparachutist.16. AB – Parachutist is decelerating, the faster he falls the greater the air resistance he experiencesuntil atBC – air resistance equals weight, balanced forces, so that parachutist falls at constant (terminal)velocity of roughly 60 m/s.CD – at C the parachute opens whereupon the air resistance increases, deceleration occurs, untilatDE – the parachutist reaches a smaller and safer terminal velocity.17. volume = 3 m 3 , mass = 57.9 g, density = ?mass 57.9density = 19.3 g/cm 3volume 3Consulting table: substance = gold18. a) volume = 20 cm 3 , mass = ?, density = 2.7 g/cm 3mass = density x volume= 2.7 x 20= 54 gb) volume = ?, mass = 54 g, density = 2.7 g/cm 3mass 54volume = 20 cm 3density 2.719. volume = 15 cm 3 , mass = 120 g, density = ?mass 120volume = 8 cm 3density 1520. volume = 10 m x 5 m x 3 m = 150 m 3 , mass = ?, density = 1.26 kg/m 3mass = density x volume= 1.26 x 150= 189 g21. volume = (35 -15) = 20 cm 3 , mass = 60 g, density = ?mass 60density = 3 g/cm 3volume 2022. volume = 0.8 m 3 , mass = ?, density = 800 kg/m 3mass = density x volume= 800 x 0.08= 64 g23. volume of air = 100 cm 3 , mass of air = (351.2 – 350) = 1.2 g, density = ?mass 1.2density = 0.012 g/cm 3volume 1009

GCSE Physics for CCEA second edition24. a) volume of rivets = 70 – 50 = 20 cm 3b) volume of 1 rivet = 20/100 = 0.2 cm 3c) volume of air = 20 cm 3 , mass of air = 180 g, density = ?mass 180density = 9 g/cm 3volume 2025. a) clockwise moment = force x perpendicular distance to pivot= 150 x 0.9= 135 Nmb) clockwise moment = anticlockwise moment135 = F x 1.35135F = 100 N1.3526. clockwise moment = anticlockwise moment3 x X = 4 x 364 x 36X = = 48 cm327. a) moment exerted by boy = force x perpendicular distance to pivot= 100 N x 4 m= 400 Nmb) If in equilibrium: moment exerted by man = moment exerted by boy= 400 Nmc) moment exerted by man = force x distance to pivot400 = force x (4 – 3)= force x 1force = 400 N28. a) clockwise moment of 5 N force = 5N x 40 cm= 200 Ncmb) anticlockwise moment = clockwise momentweight x 25 cm = 200 Ncm200weight 25= 8N29. clockwise moment = anticlockwise momentF x 225 = 600 x 75600 x 75F 225= 200 N10

GCSE Physics for CCEA second edition30. clockwise moment = anticlockwise momentF x 0.6 = 100 x 0.3100 x 0.3=0.6= 50 N31. a) Where medians of triangle meet, middle of rectangle.b) In the centre of the cut-out circle, ie., not in the plastic sheet itself.32. a) It is a point through which the whole weight of the object appears to act.b) i) The centre of gravity of the pencil and the penknife is on a line below the point of thepencil.33. a)ii) The penknife and pencil would topple.b) Low centre of gravity and wide wheel base.34. a)b) The whiskey glass.c) Lower centre of gravity and wider base.35. a)i) unstable ii) neutral11

GCSE Physics for CCEA second editionb) i)36. a)ii) B.iii) Lower centre of gravity and wider base.XZYb)centre of gravityoutside laminaExam questions (page 35)1. a) Density is the ratio of the mass to volume. (2 marks)b) See Figure 12a page 23. (4 marks)c) Volume = 2.4 cm 3 , mass = 46g, density = ?mass 46density = 19.2g/cm 3volume 2.4(3 marks)d) Gold. (1 mark)2. a) i) volume = l x b x d= 1.8 x 1.2 x 0.1= 0.216 m 3 (4 marks)12

GCSE Physics for CCEA second editionmass 520ii) density = 2407.4kg/m 3volume 0.216This density is greater than 2350 kg/m, therefore this slab will be suitable. (4 marks)NB: mass of slab = 520kg, not 520g as in question.b) i) The centre of gravity is a point through which the whole weight of the body appears toact.(1 mark)ii) moment = force x perpendicular distance to pivot= 1500N x 0.4m= 600Nm (5 marks)iii) anticlockwise moment = clockwise momenteffort x (0.4 + 0.7) = 600effort x 1.1 = 600600effort = 545N (4 marks)1.1iv)upward forces = downward forcesreaction + 545N = 1500Nreaction = 1500 – 545= 955N (2 marks)13

GCSE Physics for CCEA second editionIn-text questionsChapter 3 Energy1. Any three from: coal, oil, (natural) gas, lignite, peat (turf).2. Sound, electricity and heat are energy forms. The others are not forms of energy.3. Hydroelectricity, wind and tides are renewable. Gas, oil and coal are non-renewable.4. The solar cells change light energy into electrical energy. The battery stores chemical energy.As the propellers turn they change electrical energy into useful kinetic energy. As the modelaircraft gains height, it gains gravitational potential energy. The model aircraft crashes into theground. As it does so, it produces wasted heat and sound energy.5. Renewable resources are in limitless supply because they are replaced by nature in less than ahuman lifetime.6. ▪ Both use water to produce steam which drives a turbine.• A nuclear power station uses fission of uranium to produce heat and the waste products aredangerously radioactive.• A fossil fuel power station burns fossil fuels to produce heat. One of the waste products,carbon dioxide, is a major contributor to global warming.7. The waste will be dangerously radioactive for a very long time and there can be no guarantee thatit will not leak. There is also the possibility of seismic activity (earthquakes) bringing it to thesurface.8. Carbon dioxide.9. Prevailing winds blow sulphur dioxide from Britain to Norway.10. See table and text on pages 39–40.11. See table and text on pages 39–40.12. Open-cast mining for lignite would ruin the beauty of a naturally very attractive area.13. See text on pages 37 and 40.14. Conserve fossil fuels, wind is renewable, less atmospheric pollution leading to global warming.15. The materials used to generate electricity (fossil fuels and uranium) themselves produce verypolluting waste products.14

GCSE Physics for CCEA second edition16.Device/situation Input energy form Useful outputenergy formMicrophone sound energy → electrical energyElectric smoothing iron electrical energy → heat energyLoudspeaker electrical energy → sound energyCoal burning in an open fire chemical energy → heat energyA weight falling towards the gravitational→ kinetic energygroundpotential energyA candle flame chemical energy → heat energy andBattery-powered electric drill chemical energy →electricalenergy →light energykinetic energy17. work (in J) = Force (in N) x distance (in m) = (100 x 10)N x 5.5m = 5500J18. work (in J) = Force (in N) x distance (in m) = 60N x 20m = 1200J19. a)useful energy outputefficiency total energy input750 = 0.751000b) Heat is lost to the metal of the boiler, to the surroundings and in the hot smoke through thechimney. Sound is lost to the environment.20. efficiency 21.useful energy outputtotal energy inputSince, by the Law of Conservation of Energy, energy is neither created nor destroyed, the usefulenergy output can never be greater than the total energy input.useful energy outputefficiency total energy input140 0000.28 total energy input140 000total (chemical) energy input = 500 000kJ0.2822. energy (in J) = power (in W) x time (in s) = 3600W x (5 x 60)s= 1 080 000 J23. a) weight = mg = 1500kg x 10N/kg = 15 000Nb) work = force x distance = 15 000N x 12m = 180 000Jc)d)time (in s) work (in J)power (in W)distance (in m)speed (in m/s) time (in s)180000 = 60s300012 = 0.2m/s6015

GCSE Physics for CCEA second edition24. a) work (in J) = force (in N) x distance (in m) = 1000N x 0.4m = 400Jb)useful energy outputefficiency total energy input400 = 0.33120025. KE = ½ mv 2 = ½ x 120 x 3000 2 = 540 000 000 J26. GPE of rubber = mgh = 0.050 kg x 10 N/kg x 280 m = 140 JKE of shell = ½ mv 2 = 0.5 x 0.010 x 150 2 = 112.5 JComment: if energy losses are ignored, KE of shell is less than that of rubber as it hits theground.27. KE of tanker = ½ mv 2200 000 000 = 0.5 x 100 000 000 x v 2v 2 = 4v = 2 m/s28.Height aboveground in mGravitationalpotentialenergy in JKinetic energyin JTotalenergy in JSpeed in m/s5.0 100 0 100 04.0 80 20 100 4.473.2 64 36 100 6.01.8 36 64 100 8.00.0 0 100 100 10.029. KE of car = ½ mv 2160 000 = 0.5 x 800 x v 2v 2 = 400v = 20 m/s = (20 x 60) metres/min = 1.2 km/min = 1.2 x 60 km/hr = 72 km/hr30. GPE = mass x gravitational field strength x height176 = 2 x g x 10g = 176 ÷ 20 = 8.8 N/kgBy inspection of the table, the planet was Venus.31. a) KE (in J) as ball rises from ground = GPE of ball at its maximum height10 J = 0.2 kg x 10 N/kg x height in metresHeight = 10 ÷ 2 = 5 metresb) In practice, energy is lost as heat and sound against air resistance as the ball rises. So, not allof the KE of the ball is converted into GPE.useful energy output ( 25 20)32. a) efficiency = 0.2total energy input 25b) The principle of Conservation of Energy.33. a) useful energy output = efficiency x total energy input = 0.3 x 2000 = 600 Jb) total wasted energy = 2000 – 600 = 1400 Jwasted heat energy = 0.9 x total wasted energy = 0.9 x 1400 = 1260 Jpercentage of the input energy lost as heat = (1260 ÷ 2000) x 100% = 63%16

GCSE Physics for CCEA second editionExam questions (pages 55–57)1. a) Kinetic energy and gravitational potential energy. (2 marks)b) i) Input kinetic energy of wind → Useful output electrical energy (2 marks)ii) Wind energy is in almost limitless supply because it is replaced so quickly by nature.(1 mark)iii) Other renewables are wave energy and solar energy.(2 marks)c) Gravitational potential energy → Kinetic energy → Electrical output energystored in upper lake in moving water from the power station (3 marks)2. Advantage: tidal energy has low running costs (but huge set-up costs).Disadvantage: while the tides (unlike wind and waves) are predictable, they vary from day to dayand month to month. This makes them unsuitable for producing a constant daily amount ofelectrical energy.(2 marks)3. a) i) Oil is a non-renewable fuel because it is not being replaced by nature. (2 marks)ii) Wind energy is renewable because it is in almost limitless supply because it is replacedso quickly by nature.(2 marks)iii) Non-renewable resources, such as coal, oil and gas are generally more reliable thanrenewable energy sources like wind, waves and solar energy.(1 mark)b) i) GPE lost per second = mgh = 100 000 000 x 10 x 50 = 50 000 000 000 J/s or 5 x 10 10 J/s(3 marks)ii) Maximum power output = (0.8 / 100) x 50 000 000 000 = 400 000 000 W (3 marks)iii) The water flowing over the falls comes from rainfall. Rainfall occurs as part of the watercycle in which water in the oceans is evaporated by the sun, rises and condenses to formclouds. The clouds are driven by the wind over land and the water falls as precipitation toform rivers and lakes. Some of this water passes over the falls.(2 marks)c) i) useful power output = efficiency x electrical power input = 0.6 x 500 = 300 W(3 marks)ii) 300 J(1 mark)iii) power = force in rope x distance moved per second300 = 1200 x distance moved per secondconstant speed of vehicle = distance moved per second = 300 ÷ 1200 = 0.25 m/s(3 marks)4. a) work = force x distance = 8000N x 1.8m = 14 400J (3 marks)b)c)time workpowerpower input26000 = 5s (3 marks)5200useful power outputefficiency5200 = 20 000 W = 20 kW (3 marks)0.2617

GCSE Physics for CCEA second edition5. work = force x distance = 550N x 3m = 1650J (3 marks)6. a) work = force x distance = 24 000N x 40m = 960 000J = 960kJ (3 marks)b)c)workpower time960 = 48kW (3 marks)20useful energy outputefficiency total energy input960 = 0.8 (3 marks)12007.d)EnergyPotential energy of the toptramcarKinetic energy of the toptramcarKinetic energy of the bottomtramcarPotential energy of thebottom tramcarHeat energyIncreases/decreases/unchangedDECREASESUNCHANGEDUNCHANGEDINCREASESINCREASESQuantity Increases Decreases ConstantSpeed of ball✓Potential energy of ball ✓Total energy of ball✓Kinetic energy of ball✓(5 marks)(4 marks)8. a) Grade A dishwasher costs less to run than D. (1 mark)b) Electrical energy is converted into USEFUL HEAT energy and USEFUL KINETIC energyand WASTED SOUND energy.(4 marks)c) A shopper might not always buy the most efficient appliance which a shop has for salebecause the most efficient appliance might be the most expensive.(2 marks)18

GCSE Physics for CCEA second editionIn-text questionsChapter 4 Radioactivity1. 1. 6 protons, 8 neutrons, 0 electrons (electrons are not in the nucleus).232.11Na3. The nuclei of isotopes have the same atomic number (same number of protons), but they have adifferent mass number (a different number of protons + neutrons).4. a) β decay (no change in mass number, but change in name of nucleus)b) α decay (reduction in mass number of 4)c) α decay (reduction in mass number of 4)5. a) 210b) 212c) 2106. a) Decreases by 4b) Decreases by 2c) Unchangedd) Increases by 1Exam questions (pages 72–3)1. a)Particle Mass Charge Number LocationElectron 1/1840 –1 6 Orbiting nucleusNeutron 1 0 6 In the nucleusProton 1 +1 6 In the nucleus(7 marks)b) i) A nucleus is radioactive if it decays by emitting α particles, β particles or γ radiation.(2 marks)ii) Radon is radioactive and it emits radiation which can cause serious damage to lungtissues. The decay products might also lodge permanently in the lungs. These decayproducts are also radioactive and will go on causing damage to tissues. This damage maylead to cancers.(2 marks)ii) Nuclei with the same number of protons but a different number of neutrons are calledisotopes.(2 marks)c) i) Points plotted at: (0, 800), (20, 400), (40, 200), (60, 100), (80, 50) (5 marks)ii) Curve passing through these points.(1 mark)19

GCSE Physics for CCEA second editiond) i) A beam of beta particles will all be absorbed by a sheet of aluminium several mm thickplaced in their path.(1 mark)ii)(3 marks)iii) First measure the background count rate. Then measure the count rate for increasingthicknesses of aluminium.(3 marks)iv) Increase the thickness of the aluminium between the source and the Geiger tube andmeasure the corresponding count rate until the count rate is equal to the backgroundcount. Then measure the thickness of the aluminium – this thickness is the range of betaparticles in aluminium.(2 marks)v) (2 marks)14 14 02. a)6C 7N-1β(4 marks)b) Firstly, alpha radiation is so ionisng that it is likely to cause serious harm to tissues within thebody. Secondly, alpha radiation has such a small range that it cannot leave the body and bedetected by the camera.(2 marks)c) i) Background activity comes from rocks containing uranium and other radioactiveelements, the waste products from nuclear power stations and Nuclear MedicineDepartments in hospitals and cosmic rays from space. To obtain the corrected count ratethe experimentalist subtracts the background count rate from the measured count rate.Corrected count rate = Observed count rate less Background count rate. (2 marks)20

GCSE Physics for CCEA second editionii)(5 marks)iii) Half life = time taken for activity to fall from original value to half of original value.From graph, the half life is 29 seconds.(2 marks)3. a) i) In alpha decay the mass number decreases by 4 and the atomic number decreases by 2.(2 marks)ii) In beta alpha decay the mass number remains the same and the atomic number increasesby 1.(2 marks)b)Element(symbol)AtomicnumberMassnumberDecaysby emittingLeavingelementU 92 238 ThTh 90 234 PaPa 91 234 UU 92 234 ThTh 90 230 RaRa 88 226 RnRn 86 222 PoPo 84 218 PbPb 82 214 BiBi 83 214 Po(3 marks)c) Student’s graph. (5 marks)d) Gamma emission gives no change to atomic number and mass number. (1 mark)e)23823423423092U and92U are isotopes;90Th and90Th are isotopes. (2 marks)4. a) i) The half-life of an isotope is defined as the time taken for its radioactivity to fall by half.(1 mark)ii) Nuclei with the same number of protons but a different number of neutrons isotopes.(1 mark)b) Student’s graph. (4 marks)21

GCSE Physics for CCEA second editionc) Half-life = 21 days (2 marks)d) Three weeks is 1 half-life. So one half-life BEFORE arrival, the mass of the uranium presentin the sample would be double what it was when it arrived; so the mass of uranium presentwould have been 2 x 100 = 200 grams.(2 marks)5. One hour is 60/12 = 5 half lives, so proportion left after 1 hour is 1/2 5 = 1/32 of material.(3 marks)6. Radioactivity is a spontaneous, random process governed by the laws of probability. Just as oneis unlikely to obtain exactly 3 heads from 6 tosses of a fair coin, so the count from a long halflifesource is unlikely to be exactly the same in each of four 10 second intervals. (2 marks)22

GCSE Physics for CCEA second editionIn-text questionsChapter 5 Waves, sound and light1. a) Energy flows from A towards B.b) In a longitudinal wave, X vibrates parallel to the axis of the slinky.c) In a transverse wave, X vibrates perpendicular to the axis of the slinky.d) Another example of a transverse wave is a water wave.2. a) = 60 ÷ 4 = 15 cmb) number of waves pass the marker in 1 second = 10 ÷ 4 = 2.5c) 2.5 Hzd) v = f = 2.5 Hz x 15 cm = 37.5 cm/s3. a) A lightning flash is generally seen before thunder is heard because light travels faster in airthan sound.b) distance = speed x time = 330 m/s x 4 s = 1320 m4. total distance travelled by sound = speed x total time = 330 m/s x 6 s = 1980 mdistance to cliff = ½ x total distance = ½ x 1980 = 990 m5. a)Frequency (Hz) 680 440 170 136 85 68Wavelength (m) 0.5 1.0 2.0 2.5 4.0 5.01/Wavelength (m -1 )2.0 1.0 0.50 0.40 0.25 0.20b) Graph: line of best fit is a straight line through the origin.c) Incorrect point is (1.0, 440)d) directly proportionale) The value of f for all table values (except the second) is 340 m/s.6. a) wavelength = 14 cm ÷ 6 = 2.33 cmb) distance between ripple A and ripple F = 2.33 x 5 = 11.65 cmspeed of waves distancetime11.65 = 1.165 cm/s10frequency speedwavelength1.165 = 0.5 Hz2.3323

GCSE Physics for CCEA second edition7.On reflection from deep water intoshallow waterOn reflection from a barrierProperty Increases/Decreases/Does not change Increases/Decreases/Does not changeWavelength DecreasesDoes not changeFrequency Does not change Does not changeSpeed Decreases Does not change8. 0°9. 50°10. 65°11.So that motorists will see the word “AMBULANCE” when they see the ambulance in their rearviewmirrors.12. Angle of reflection at M 1 is 30 o , so angle between reflected ray and M 1 is 60 o .Angle between incident ray to M 2 and mirror M 2 is 30o, so angle of incidence at M 2 is 60 o .Angle of reflection at M 2 is 60 o . The ray incident on M 1 is parallel to the ray reflected from M 2 .13. 0°. The ray is reflected back along the path of the incident ray.14. i) Light is fastest in air.ii) Light is slowest in B. (Light bends towards normal when it leaves air and enters B, so light isslower in B than in air. Light bends away from the normal when it leaves B and enters A, solight is faster in A than in B. Light bends even further away from the normal when it leavesA and enters air, so light is faster in air than in A.)15. See Figure 29 on page 92.16. a) Ray diagram similar to first diagram in table on page 96.b) Image is 6 cm from lens, but on same side as the object.c) Image is enlarged, erect and virtual.17. Focal length is 12 cm.18. a) Minimise exposure to sunlight by remaining indoors when sun is hottest. Use high sunprotection cream (high SPF cream) on skin when in sunshine.b) To detect forgeries of banknotes and to kill bacteria in water chillers.19. a) Infra red light is used in toasters in kitchens and in PIR (passive infra red) systems to detectintruders and burglars.b) Infra red light can burn the skin.24

GCSE Physics for CCEA second edition20. Electromagnetic waves can travel in a vacuum; in a vacuum all electromagnetic waves travel atthe same speed.21. a) radio wavesb) X-rays22. speed = f = 200 000 Hz x 1500 m = 300 000 000 m/s = 300 000 km/sdistance 900time = 0.003 sspeed 300000Exam questions (pages 105–7)1. a) i) The diagram shows 3 complete wavelengths cover 60 m. Each wavelength is therefore60/3 = 20 m. (1 mark)ii) Frequency is the number of waves passing a fixed point in 1 second. (1 mark)iii) frequency = number of waves passing in 1 second = 10/25 = 0.4 Hz (1 mark)iv) v = f = 0.4 x 20 = 8 m/s(1 mark)b) i) See page 79. (1 mark)ii) See page 79.(2 marks)iii) The reflected waves have been refracted as they pass from deep water into shallow water.In shallower water they have a smaller speed, but an unchanged frequency. Theytherefore have a smaller wavelength, so their wavefronts are closer together. (2 marks)2. a) i) Vibrating (1 mark)ii) The skin is vibrating with a larger amplitude.(1 mark)iii) The cone is making more vibrations per second.(1 mark)b) i) He could become deaf (or become hard of hearing). (1 mark)ii) They could fit double (or triple) glazed windows in their homes.(1 mark)c)StatementWavesCan cause sunburn and skin cancer UltravioletCan heat foodInfrared or microwavesHave the greatest wavelength Radio wave(2 marks)3. a) i) Dispersion (1 mark)ii) See Figure 30 on page 92.(2 marks)iii) Each colour in white light travels at a different speed in glass and therefore each colourbends by a different amount. Red slows down least and violet slows down most.(2 marks)b) i) See page 99. (2 marks)25

GCSE Physics for CCEA second editionii) See page 99.(1 mark)iii) f = 2.7 cm(1 mark)iv) Magnified and upside down(3 marks)4. a) The first sound Tom heard came directly from Sean 200 m away. The second sound was theecho from the cliff. In this case the sound travelled 350 m to the cliff and the reflected echotraveled a further 150 m back to Tom.(2 marks)b)distancetime speedTom hears the first sound after 200/340 = 0.588 seconds. Tom hears the second sound after500/340 = 1.471 seconds. Time interval = 1.471 – 0.588 = 0.883 seconds. (5 marks)5. a) A: Transverse; B: Longitudinal. (2 marks)b) Energy (1 mark)c) X vibrates vertically, at 90° to the direction in which the wave is travelling. (2 marks)d) 0.3 m (1 mark)e) 0.4 m (1 mark)f) 3 Hz (1 mark)g) v = f = 3 x 0.4 = 1.2 m/s (3 marks)6. a) A transverse wave is one in which the particles vibrate at 90° to the direction in which thewave is travelling.(2 marks)b) X-rays – Detects broken bonesUltra-violet light – Detects banknote forgeriesInfra-red light – Night-time photographyRadio waves – Long distance communicationsMicrowaves – Fast food preparation(5 marks)7. a) See text. (1 mark)b) angle of incidence = angle of reflection = 63° (2 marks)c) Reflected ray from M 2 is parallel to incident ray on M 1 (2 marks)26

GCSE Physics for CCEA second editionIn-text questionsChapter 6 Electricity1. a) Static electricity is the study of stationary charges.b) Positive and negative charges.c) Like charges repel, unlike charges attract.2. a) Free electrons move from the cloth (which is now deficient of negative charge and sobecomes positively charged) to the polythene cloth (which now has an excess of freeelectrons and so becomes negatively charged).b) Charging by friction.3.Material of rod Bead movement Charge on rodPositive Negative UnchargedPerspex Repelled ✓Cellulose acetate Repelled ✓Polythene Attracted ✓Steel None ✓4. a) Useful: photocopier; paint spraying of cars.b) Nuisance: clothes stick together when removed from tumble dryer; ‘shocks’ from walkingacross a nylon carpet and then touching door handle.c) Dangerous: being struck by lightning; refuelling aircraft.5. a) 3.0 A = 3000 mAb) 0.2 A = 200 mA6. a) 400 m A = 0.4 Ab) 1500 m A = 1.5 A7. a) current = 6 A, time = 10 s, charge = ?charge = current x time= 6 A x 10 s= 60 Cb) current = 300 m A = 0.3A, time = 1minute = 60 s, charge = ?charge = current x time= 0.3 A x 60 s= 18 C8. a) current = ?, time = 5 s, charge = 100 Ccharge = current x time100 C = current x 5 scurrent = 100 ÷ 5 = 20 A27

GCSE Physics for CCEA second editionb) charge = 500 mC = 0.5 C, time = 50 s, current = ?charge = current x time0.5 C = current x 50 scurrent = 0.5 ÷ 50 = 0.01 Ac) charge = 60 μC = 0.000006 C, time = 200 s, current = ?charge = current x time0.000006 C = current x 200 scurrent = 0.000006 ÷ 200 = 0.3 x 10 -6 A = 0.3 μA9. Two volts means 2 joules of energy are supplied to each coulomb of charge that the cell supplies.10. energy = 9 J, charge = 6 C, voltage = ?energy 9voltage = 1.5Vcharge 611. energy = ?, charge = 3 C, voltage = 18 Venergyvoltage chargeenergy18 3energy = 18 x 3= 54 J12. energy = 150 J, charge = 25 C, voltage = ?energy 150voltage = 6 Vcharge 2513. a) Voltmeter, since it is in parallel.b) 12 V = 5V + ?? = 12 – 5= 7 Vc) 12 V means 12 joules of energy are supplied to each coulomb of charge.d) 7 volts are dropped across motor, therefore 7 joules of energy are deposited by each coulombof charge that passes through the motor.14. a)b)15. a) Light Dependent Resistorb)c) The resistance of an LDR decreases when light is shone on it.28

GCSE Physics for CCEA second edition16. current = ?, resistance = 10 Ω, voltage = 20VV = I x R20V = I x 10 ΩI = 20V ÷ 10 Ω = 2 A17. current = 3 A, resistance = ?, voltage = 15 VV = I x R15V = 3 A x ?R = 15 V ÷ 3 A = 5 Ω18. current = 2 A, resistance = 25 Ω, voltage = ?V = I x R= 2A x 25 Ω= 50 V19. a) current = 2.5 A, resistance = ?, voltage = 15 VV = I x R15V = 2.5 A x RR = 15 V ÷ 2.5 A = 6 Ωb) current = 2 A, resistance = 6 Ω, voltage = ?V = I x RV = 2A x 6 Ω= 12 V20. a) current = ?, resistance = 12 Ω, voltage = 6VV = I x R6V = I x 12 ΩI = 6V ÷ 12 Ω = 0.5 Ab) current = 15 A, resistance = 12 Ω, voltage = ?V = I x RV = 1.5A x 12 Ω= 18 V21. current = 100mA = 0.1 A, resistance = ?, voltage = 6 VV = I x R6V = 0.1 A x RR = 6 V ÷ 0.1 A = 60 Ω29

GCSE Physics for CCEA second edition22. a)b) No. Graph is non-linear which is necessary for Ohm’s Law.23. a)30

GCSE Physics for CCEA second editionb) No. Graph is non-linear.c)Voltage in V 0 0.1 0.2 0.3 0.4 0.5 0.6 0.9Current in mA 0 0.1 0.1 0.1 0.1 1.5 73 250Resistance in Ω 0 1000 2000 3000 4000 333.3 8.219 2.824. a) Simple series circuitR = R 1 + R 2= 6 Ω+ 5 Ω= 10 Ωb) Simple parallel circuit1 1 1 RTR1R21 1 2 1 6 6 6 3R T = 3 Ωc) Simple series circuitR T = R 1 + R 2 + R 3= 2 Ω + 4 Ω + 6 Ω= 12 Ωd) Simple parallel circuit1 1 1 RTR1R21 1 3 1 12 6 12 4R T = 4 Ω product e) RT R3 sum = 2 + 1= 3 Ω 1 1 f) RT R3R1R2 4 4 R T 5 4 4 = 2 + 5= 7 Ω31

GCSE Physics for CCEA second edition product g) R T 3 sum 2 2 R T 3 2 2 = 7 Ωh) We must do top branch of circuit first: 2 Ω + 2Ω = 4 Ω product R T sum 4 4 R T = 2 Ω 4 4 product i) R T sum 3 6 R T = 2 Ω 3 6 j) In effect, there are three series resistors when we reduce the two parallel networks 4 6 9 18 R T + 1.6 Ω + 4 6 9 18 = 2.4 + 1.6 + 6.0= 10 Ω25. The 3 resistors in series = 1 + 2 + 3 = 6ΩThe 3 resistors in parallel:1 1 1 1 R T R1R 2 R 31 1 1 1 2 36 3 2 11 6 6Therefore R T = 6/11 Ω1 Ω and 2 Ω in parallel with 3 Ω in series = 3 ⅔ Ω1 Ω and 3 Ω in parallel with 2 Ω in series = 2 ¾ Ω2 Ω and 3 Ω in parallel with 1 Ω in series = 2 1/5 Ω1 Ω and 2 Ω in series and in parallel with 3 Ω = 1.5 Ω1 Ω and 3 Ω in series and in parallel with 2 Ω = 1.33 Ω etc., etc26. a) i) total resistance = 2 + 4 + 6 = 12 Ωtotal voltage = 3VV 3total current drawn 0.25AR 1232

GCSE Physics for CCEA second editionii)total resistancetotal voltage = 8 Vtotal current drawnproductsumVR64 4 168 2A4b) The 8Ω resistors are in parallel, so the voltage dropped will be the same voltage ie., 8V.121227. a) i) total resistance 6 12 12total voltage = 9 V9total current 1.5 A6A 1 = 1.5AA 2 = 0.75AA 3 = 0.75Aii)total resistance66 44 6 6 4 4= 3 + 2= 5 Ωtotal voltage = 10 VV 10total current 2AR 5A 3 = 2AA 1 = 1AA 2 = 1Ab) Since each 6 Ω resistor is carrying 1 A, there must be the same (V = IR) voltage of 6 Ω x 1A= 6V across each 6 Ω resistor.Similarly, since each 4 Ω resistor is carrying 1 A, there must be the same voltage of 4 Ω x 1A= 4V across each of the 4 Ω resistors.28. energy = ?, power = 1000 W, time = 1 hr = 3600senergy = power x time= 1000 x 3600= 3 600 000 J29. a) energy = 15 000 J, power = ?, time = 10 senergy 15000power = 1500 Wtime 10b) 1500 W = 1.5 kW30. current = 0.25 A, voltage = 240 V, time = 60 s, energy = ?E = V x I x t= 240V x 0.25A x 60s= 3600 J33

GCSE Physics for CCEA second edition31. a) energy = ?, power = 960 W, time = 60 senergy = power x time= 960 W x 60 s= 57 600 Jb) current = ?, voltage = 12 V, power = 960 WP = V x I960 W = 12 V x I960I = 80 A1232. current = 4 A, voltage = 240 V, power = ?P = V x I= 240 V x 4A= 960 W33. current = ?, voltage = 12 V, power = 48WP = V x I48 W = 12 V x I48I = 4 A1234.Name of applianceBulb of study lampTelevisionToasterConvector heaterShowerPower rating60 W80 W120 W2 kW3 kW35. resistance = 48, voltage = 240 V, power = ?22V 240P = 1200 WR 48PVCurrent I Resistance R VI60 240 0.25 A 960 2400.2580 240 0.33 A 720 2400.333120 240 0.5 A 480 2400.52000 240 8.33 A 28.8 2408.333000 240 12.5 A 192 24012.536. a) i) Brown.ii) Blue.iii) Green and yellow.b) i) Current will flow from the live wire, through the metal case to the person touching thecase, and then to earth. The person touching the case would be electrocuted.34

GCSE Physics for CCEA second editionii) Since the earth wire is now properly connected, the current will flow through the earthwire to the ground, melting the fuse, cutting off the current. The person touching the casewould not be electrocuted.37. a) Direct current – always flows in the same direction, from a fixed positive terminal to thefixed negative terminal of a supply. See Figure 39 b, page 133.b) Alternating current – the voltage (and hence the current) change size and direction in aregular and repetitive way. See Figure 40, page 133.38. Circuit breakers react much more quickly than fuses so protecting the user.39. a) current = ?, voltage = 230 V, power = 60WP = V x I60 W = 230 V x I60I = 0.26 A230b) A fuse rated greater than 3 A would pass too high a current which would be dangerous.40. a) current = ?, voltage = 240 V, power = 3000WP = V x I3000 W = 240 V x I3000I = 12.5 A i.e. the fuse would ‘blow’.240b) current = ?, voltage = 240 V, power = 60 WP = V x I60 W = 240 V x I60I = 0.25 A240If a 13 A fuse was used, the fuse would not ‘blow’ until the current exceeded 13 A. So afaulty study lamp would electrocute user.c) current = ?, voltage = 240 V, power = 800 WP = V x I800 W = 240 V x I800I = 3.33 A240So a 5A fuse would be preferable.41. Consider 1 bulb:current = ?, voltage = 240 V, power = 60 WP = V x I60 W = 240 V x I60I = 0.25 A240So you should use less than 20 bulbs so that the fuse would not be overloaded.35

GCSE Physics for CCEA second edition42. a)Device Power (W) Current drawn (A)Kettle 2400 2400 10.43230Washing Machine 3000 2300 12.5230Television 800 800 3.48230Toaster 1300 1300 5.65230So total current drawn = 32.06 Ab) Total current drawn (32.06 A) is much greater than the 13 A fuse in extension lead, so thefuse would ‘blow’ and none of the appliances would work.43. energy (in kW h) = power (in kW) x time (in hours)a) energy = 0.1 kW x 12 hr= 1.2 kWhb) energy = 0.25kW x 4 hr= 1 kWhc) energy = 2.4 kW x 1 / 12 hr= 0.2 kWh44. Lamp: 1.2 kWh @ 12p per unit = 14.4pTelevision: 1 kWh @ 12p per unit = 12pKettle: 0.2 kWh @ 12p per unit = 24p45. a) current = 15 A, voltage = 230 V, power = ?P = V x I= 230 V x 15 A= 3450 Wb) number of units used = power (in kW) x time (in hr)= 3.45 kW x 0.166 hr= 0.575 units @ 12p per unit= 6.9pExam questions (pages 139–42)1. a) Lightning strike would mean a large current would flow through building to earth. Fire ordestruction of buildings could happen.(2 marks)b) i) Friction between balloon and cloth cause electrons to move from the balloon to the cloth.The balloon would have a deficiency of electrons and hence would become positivelycharged.(3 marks)ii) The charges on the balloons are both positive hence the balloon repel each other. Likecharges repel.(4 marks)36

GCSE Physics for CCEA second editionc) i)X(3 marks)ii) The currents decreased.(1 mark) 63 d) i) R Total 8 6 3 = 8 + 2= 10 Ω (4 marks)ii)VI R5 = 0.5 A (3 marks)10(3 marks)iii) V = IR = 0.5 x 8 = 4 Viv) power = V x I= 4 V x 0.5 A= 2 W (4 marks)v) Since there are 4 V across the 8 Ω resistor then there must be (5 – 4) V = 1 V across the6Ω resistor.(2 marks)vi) One volt, since resistors in parallel have the same voltage across them. (1 mark)2. a) i)X(2 marks)product 0.60.3 0.18ii) R r = 0.2 Ω (3 marks)sum 0.6 0.3 0.9iii) Brightness remains the same because the voltage across bulb has not changed. (2 marks)37

GCSE Physics for CCEA second editionb) i)AAV(3 marks)ii)(4 marks)3. a) i)iii) 70 mA(1 mark)V 0.4iv) R = 8 Ω (4 marks)I 50v) Yes, gradient is constant. (2 marks)vi) To keep temperature of wire as low as possible, otherwise resistance would increase.(1 mark)XX(4 marks)38

GCSE Physics for CCEA second editionii) Parallel.(1 mark)iii) Bulbs in parallel will have 1.5 V across each of them i.e. 1.5V in this case. So when onebulb is removed, the second bulb will still have 1.5 V across it, so its brightness will notchange.(2 marks)iv) voltage = 1.5 V, current = 0.3 A, resistance = ?V = IR1.5 = 0.3 x R1.5R = 5 Ω (4 marks)0.3b) i) 3 V (2 marks)ii) voltage = 3 V, current = ?, resistance = 5 ΩV = IR3 = I x 53I = 0.6 A (4 marks)5iii) Bulb will be brighter.(2 marks)c) i) The resistance increases because length of resistance wire increases. (2 marks)ii) Current decreases as the resistance has increased.(2 marks)4. a) i)AXV(2 marks)ii)VR IVR I0.5 = 5 Ω0.13.2 = 8 Ω (3 marks)0.439

GCSE Physics for CCEA second editioniii)(2 marks)iv) The gradient of the graph increases as the current increases because the resistance of bulbfilament increases as the current increases. The reason for this is that temperature of thefilament wire increases.(2 marks)b) i) power = 2000 W, voltage = 240 V, current = ?P = V x I2000 W = 240 V x I2000I = 8.33 A240Fuse size = 13 A(4 marks)ii) live = 8.33 A; neutral = 8.33 A; earth = 0 A(1 mark)iii) A current of up to 13 A would flow through person touching casing of fire. (1 mark)iv) Earth wire should be connected to metal body of electric fire.(1 mark)v) The fuse must be connected to live wire. (1 mark)vi) The 13 A current would flow through fuse and earth wire to ground. The fuse will blowisolating the device from the high voltage.(1 mark)5. a) i) 12107 – 11847 = 210 units (1 mark)ii) 1 unit = 12 p210 units = 210 x 12 = 2520 p = £25.20 (2 marks)b) i) A = fuse (1 mark)ii) 2(1 mark)iii) 1 = blue; 2 = brown(2 marks)c) i) As thickness increases, resistance decreases. (2 marks)ii) As length increases, resistance increases.(2 marks)d) i) Draw lines to connect points 1 to 2 and 4 to 6; or draw lines to connect points 1 to 3 and 4to 5.(2 marks)40

GCSE Physics for CCEA second editionii) The current flows from positive terminal to 1 to 2 to 6 to 4 to the negative terminal.(2 marks)e) i) Parallel. (1 mark)productii) R rsumiii)555 525 = 2.5 Ω (2 marks)10(1 mark)6. a) i) 240 V means 240 J deposited by each coulomb of charge that passes through TV. 80 Wmeans 80 J of energy consumed by the TV in each and every second. (2 marks)ii) power = 80 W, voltage = 240 V, current = ?P = V x I80 W = 240 V x I80I = 0.33 A (3 marks)240iii) 1 A fuse would be the safest size of fuse to select. The other fuses will allow currentswhich would be too large.(2 marks)iv) voltage = 240 V, current = 0.33 A, resistance = ?V = IR240 = 0.33 x R240R = 720 Ω (3 marks)0.33v) Blue wire to the left pin and brown wire to the right pin. (3 marks)vi) The live wire.(1 mark)vii) To isolate the appliance and user from high voltage.(1 mark)viii)All the live electrical wires and circuits inside the TV are insulated by the non-metalliccasing of the TV.(3 marks)b) i) energy = power x time= 8 x 2= 16 units @ 12p per unit= 192 p= £1.92 (3 marks)41

GCSE Physics for CCEA second editionii) 15m means resistance will be 3 times bigger. Similarly the cross-sectional area will be 3times bigger, therefore the resistance will be 3 times smaller. The combined effect is thatthe resistance will be the same as before i.e., 0.045 Ω.(6 marks)iii) The current is small in the cables so that the (I 2 R) heating effect is smaller. (2 marks)42

GCSE Physics for CCEA second editionIn-text questionsChapter 7 Electromagnetism1. a) Use a larger current; use more turns of wire; put a soft iron rod into the middle of thesolenoid.b) Lifting and dropping magnetic materials like iron and steel in scrap yards.2. a) The direction of the magnetic lines of force are from the N-pole of the magnet to the S-pole.b) The brass rod will move to the right, parallel to the brass rails.c) The brass rod will move to the left.d) Assuming the magnet is also in its original position i.e., as in part (a), the brass rod will moveto the left.3. a) ‘d.c.’ means direct current.b) The direction of the force on AB is vertically downwards.c) The direction of the force on CD is vertically upwards.d) The forces form a couple which results in a clockwise moment about the axis, causing thecoil to rotate.e) The force on side BC is zero, since the current in BC is parallel to the magnetic field lines.4. a) There is a rate of change of flux (magnetic field lines) cutting which induces an e.m.f. whichresults in an induced current.b) The induced current will flow in the opposite direction.c) Julie should move the wire faster.d) No current will be induced because the wire is moving parallel to the magnetic field lines andis no longer cutting the field lines.5. Power is transmitted at high voltage to minimise the current in the cables which reduces heatlosses, sometimes referred to as ohmic losses, in the transmission system.6. a) Primary coil; soft-iron laminated core; secondary coil.b) The core transfers energy, in the form of an oscillating magnetic field, from the primary coilto the secondary coil.c) Soft iron is the best material for magnetic field lines to pass through.7. If d.c. was used there would be no changing magnetic field produced by the primary coil,consequently there would be no induced e.m.f. in the secondary coil.43

GCSE Physics for CCEA second edition8. V P = 240 V, V s = 48 V, N P = 2000 turns, N s = ?VPNP 240 2000 VSNS48 NS200048N S = 400 turns2409. V P = 4 V, V s = ?, N P = 20 turns, N s = 80 turnsVPNP 4 20 VSNSVS80480V S = 16 V2010. a) Step-down transformer.b) All electrical appliances in the home operate at 240 V, 24000 V would seriously damageappliances and would be a health hazard to the occupants.c) Current in the supply cables would be very large causing a lot of electrical energy to bewasted as heat energy.d) V P = 24 000 V, V s = 240 V, N P = 5000 turns, N s = ?VPNP24 000 5000 VSNS240 NS5000240N S = 50 turns24 00011. a) Step-up transformer.b) V P = 25 000 V, V s = 400 000 V, N P = 1000 turns, N s = ?VPNP25 000 10 000 VSNS400 000 NS10 000400 000N S = 160 000 turns25 000c) The voltage is 400 000 V to reduce the current in the grid. This reduces the energy losses inthe form of heat so that more electrical energy reaches factories and homes.Exam questions (pages 157–9)1. a) There is a rate of change of flux linkage between the magnetic field of the magnet and thecoil of copper wire.(2 marks)b) Current is alternating. The flux linkage increases and decreases inducing a voltage whichchanges in size and direction as long as the magnet is oscillating up and down. (2 marks)c) See Figure 39 b, page 133. (2 marks)2. a) i) a.c. stands for alternating current. Alternating means that the polarity of the supplychanges sign periodically whereas direct means that the polarity remains constant.(3 marks)44

GCSE Physics for CCEA second editionii) Soft iron.(1 mark)iii) V P = 16 V, V s = ?, N P = 100 turns, N s = 50 turnsVPNP 16 100 VSNSVS5016100V S = 32 V (4 marks)50b) i) 10 steps = 20 V1 step = 2 VSo voltage will increase or decrease by 2 V.(3 marks)ii) 1 step = 50 turns10 steps = 500 turns (1 mark)iii) V P = 240 V, V s = 20 V, N P = ?, N s = 500 turnsVPNP 240 NPVSNS20 500500240N P = 6000 turns (3 marks)20iv) If a current flows which is greater than the fuse rating, the fuse will ‘blow’ protecting thedevice to which it is connected.(2 marks)c) i) Kinetic energy of fission fragments is converted into heat energy. (2 marks)ii) X = generator which converts rotational kinetic energy into electrical energy. (2 marks)d) i) Step-up; step-down. (2 marks)ii) High; low.(2 marks)iii) High voltages are used to minimise current in the grid. This reduces electrical energy lostas heat energy.(2 marks)3. a) i) See Figure 6, page 144. (2 marks)ii) See Figure 6, page 144.(4 marks)b) i) See Figure 24, page 155. (7 marks)ii) a.c. voltages.(1 mark)iii) V P = 6 V, V s = 12 V, N P = 200 turns, N s = ?VPNP 6 200 VSNS12 NS20012N S = 400 turns (4 marks)6c) The output of a power station is a high current and relatively low voltage. If this form ofenergy was transmitted directly, without a step-up transformer, the large current wouldgenerate a large amount of electrical energy in the form of heat, lost to the atmosphere.Hence there would be less energy transmitted to users.(4 marks)45

GCSE Physics for CCEA second edition4. a) i) 25 kJ of energy per coulomb. (1 mark)ii) Stepping up the voltage, decreases the current in the grid. This has the effect ofdecreasing the electrical energy lost as heat due to the resistance of the cables in the grid.(2 marks)iii) Step-down transformers must also be used before electrical energy is put into factoriesand homes.(1 mark)iv) For safety.(1 mark)b) i) energy (in kWh) = power (in kW) x time (in hours)= 0.8 kW x 0.25 hr= 0.2 kWh (4 marks)ii) 1 unit costs 12p, 0.25 units costs 3p(1 mark)c) i) 1) Momentary deflection in current meter. (1 mark)2) Momentary deflection in the opposite direction in current meter. (2 marks)ii) The needle in the current meter will oscillate at 1 Hz.(2 marks)46

GCSE Physics for CCEA second editionIn-text questionsChapter 8 The Earth and Universe1. asteroid, planet, star, galaxy, Universe.2. a) The light from distant galaxies has a longer wavelength than we would have expected.Having a longer wavelength means that it is closer to the red end of the visible spectrum.This is called ‘red-shift’.b) These galaxies are moving away from our galaxy (the Milky Way).3. Mercury, Venus, Earth, Mars, Jupiter, S aturn, Uranus, Neptune.4. The heliocentric (Sun-centred) model explains:• the apparent ‘looping’ of planets was due to the combined motion of the Earth and the planetitself;• why Venus is sometimes closer to Earth than Mars so it appears brighter, but at other timesVenus is further away than Mars and appears less bright;• why Venus and Mercury should show phases, just as our Moon does.5. The Big Bang occurred between 13 and 14 billion years ago. It was then that the Universe(matter, energy and time) came into existence. The Big Bang (or explosion) came from a tinypoint that physicists call a singularity.6. In order to explain the expansion of the Universe, Steady State theory suggests that matter isbeing created continually. Physicists are uncomfortable with this idea because it suggests that ourthoughts about energy conservation might not be correct. In addition, the theory fails to explainwhy the Universe is expanding or why there is cosmic microwave background radiation.7. At temperatures around 15 million Celsius, hydrogen nuclei collide with each other atunbelievably high speeds. At such speeds they can form new, heavier nuclei such as helium-3and helium-4. This process is called nuclear fusion and results in the production of vastquantities of heat and light energy. It occurs in stars.8. Clouds of gas and dust come together as a result of mutual gravitational attraction, but do nothave enough material for the temperature to reach 15 million °C to form a star. Such gas and dustclouds are called planetary nebulae and eventually they become planets as a result of accretiondue to gravitational attraction. The presence of a massive star may cause them to become trappedin its orbit. Since the gas and dust clouds originally spiralled in the same direction, so the planetswould orbit the Sun in same direction and in the same plane.9. Currently astrophysicists estimate the age of the Universe to be 13.75 billion years.10. When rock strata of similar ages are studied in various countries, they show remarkablesimilarity – suggesting that these countries were joined together when the rocks formed. Themost compelling evidence in favour of continental drift comes from the magnetic orientation ofthe rocks in under-ocean ridges. As the liquid magma erupts out of the gap, the iron particles inthe rocks tend to align themselves with the Earth’s magnetic field, and as it cools they set in thatposition. Every half million years or so, the Earth’s magnetic fi eld tends to swap direction. Thismeans the rocks on either side of the ridge have bands of alternate magnetic polarity.47

GCSE Physics for CCEA second edition11. Earthquakes are caused when tectonic plates slide past each other. This happens where the platesmeet.12. The Earth’s lithosphere is the lower part of the crust and the upper, solid part of the uppermantle.13. Every century the continents move apart by 1.2 cm x 100 = 120 cm =1.2 m. In 50 000 centuriesthey move apart by 50 000 x 1.2 m = 60 000 m = 60 kmExam questions (pages 175–6)1. a) i) Nebula. (1 mark)ii) Hydrogen and dust.(1 mark)iii) It compresses under its own gravity and its temperature rises appreciably. (1 mark)iv) A star.(1 mark)b) i) Nuclear fusion. (1 mark)ii) Heat.(1 mark)2.Planet Distance from Sun in millions of kilometresEarth 150Jupiter 778Mercury 58Venus 108Uranus 2870Neptune 4497Mars 227Saturn 1247(4 marks)3. a) Universe. (1 mark)b) i) Neptune. (1 mark)ii) C.(1 mark)iii) D and E.(1 mark)iv) Jupiter, Saturn, Uranus, Neptune.(2 marks)c) Nuclear fusion. (1 mark)d) The journey would take a very long time. There are logistics problems in carrying enoughfuel, oxygen, food and water for the journey.(2 marks)e) Steady State theory. (1 mark)f) i) The Big Bang occurred between 13 and 14 billion years ago. It was then that theUniverse (matter, energy and time) came into existence. The Big Bang (or explosion)came from a tiny point that physicists call a singularity.(1 mark)48

GCSE Physics for CCEA second editionii) The Universe is continuing to expand.(1 mark)4. a) Our present model is heliocentric. This means the planets orbit the Sun. The ancient theorywas geocentric. This means that the planets and the Sun orbited the Earth. In our presentmodel there are 8 planets. The ancient theory had only 6 planets because Uranus and Neptunehad not yet been discovered.(2 marks)b) Stars form when clouds of hydrogen, known as a stellar nebula, come together because ofgravity. As these clouds become more and more compressed, they start to spiral inwards andthe temperature rises enormously. Gravity eventually compresses the hydrogen so much thatthe temperature reaches about 15 million °C. At this temperature, nuclear fusion reactionsstart and a star is born. Clouds of gas and dust, called planetary nebulae, come together as aresult of mutual gravitational attraction, Such gas and dust clouds eventually become planetsas a result of accretion due to gravitational attraction.(2 marks)c) i) The arrows all point from points 1, 2 and 3 towards the centre of the Sun. (3 marks)ii) Gravitational attraction between the Sun and the comet.(1 mark)iii) Points 1 and 2 are equidistant from the centre of the Sun and therefore the size of theforce on the comet at these two positions is the same. Point 3 is further from the Sun thanpoints 1 and 2. At point 3, the force on the comet is less than at points 1 and 2. This isbecause gravitational force decreases with distance.(2 marks)iv) Kinetic energy.(1 mark)v) As the comet approaches the Sun it loses gravitational potential energy. This GPE isconverted into kinetic energy. As it moves away from the Sun it loses KE. The lost KE isconverted into gravitational potential energy.(1 mark)vi) The comet is fastest when it is closest to the Sun and slowest when it is furthest awayfrom the Sun. This is because it has most KE when it is closest the Sun. (2 marks)5. a) The light from distant galaxies has a longer wavelength than we would have expected.Having a longer wavelength means that it is closer to the red end of the visible spectrum.This is called ‘red-shift’.(1 mark)b) Red shift tells us that these galaxies are moving away from our galaxy (the Milky Way).(2 marks)6. a) i) Red shift. (1 mark)ii) Away from our galaxy.(1 mark)b) Big Bang Theory. (1 mark)c) See answer to question 4(b). (4 marks)d) The temperature near the centre of the Sun is so high that hydrogen nuclei collide with eachother at unbelievably high speeds. When they collide at such speeds they can form new,heavier nuclei such as helium-3 and helium-4. This process is called nuclear fusion andresults in the production of vast quantities of heat and light energy.(3 marks)49