Electromagnetic effects — Paper 4 · IGCSE Sciences - Co-ordinated (Double) 0654

7 (a) Fig. 7.1 shows a speed-time graph for a car over a period of 50 seconds. BB CC 4 3 speed m / s 2 1 A DD EE 0 0 10 20 30 40 50 time / s Fig. 7.1 (i) State the maximum speed reached by the car. … m / s [1] (ii) Calculate the total distance travelled by the car. Show your working. distance = … m [2] (iii) Show that the acceleration of the car during the first ten seconds is 0.4 m / s2. [1] (iv) The mass of the car is 950 kg. Calculate the force needed to produce an acceleration of 0.4 m / s2. State the formula you use and show your working. formula working force = … N [2] (b) The temperature of the air in car tyres increases during a journey. (i) Describe what happens to the motion of the air particles as the air warms up. … … [1] (ii) When the temperature of the air in the tyres increases, the pressure in the tyres increases. Explain in terms of the motion of the air particles why the pressure increases. … … … [2] (c) Relays are needed in many electrical circuits used in machines. Fig. 7.2 shows a simple relay circuit. contacts high-voltage pivot circuit soft iron soft iron coil low-voltage circuit Fig. 7.2 (i) Describe how a small current flowing in a low-voltage circuit is able to turn on the high-voltage circuit. … … … … … [3] (ii) Suggest how the use of a relay in a high-voltage circuit protects the person operating a machine. … … [1]

13 marks

Mark scheme: 7(a)(i) 4 (m / s) ; 1 7(a)(ii) area under graph / working ; 20 + 20 + 50 = 90 (m) ; 2 7(a)(iii) working ; e.g. correct substitution into formula such as 4 / 10 ; 1 7(a)(iv) force = mass × acceleration / 950 × 0.4 ; 380 (N) ; 2 7(b)(i) move faster ; 1 7(b)(ii) more frequent collisions / collide at greater speed, with tyre wall ; more force exerted on tyre walls ; 2 7(c)(i) current in low voltage circuit creates magnetic field (around solenoid) ; soft iron attracted (to magnet / solenoid) ; contacts in high voltage circuit close ; 3 7(c)(ii) so that humans, are not exposed to the high voltage circuit / operate low voltage switching circuit / owtte ; 1

This question in 0654/41 May/June 2017

11 (a) A small quantity of radioactive material is taken from a nuclear reactor. Describe how a scientist could prove that the material is releasing γ-rays but not α-particles or β-particles. … … … … … [3] (b) The nuclear fuel used in a power station is plutonium-239. 239 94 Pu decays by α-emission to produce an isotope of uranium. Use the correct nuclide notation to write a symbol equation for this decay process. 239 Pu → … + … 94 [2] (c) The electricity produced in a nuclear power station is transferred from the power station to a nearby town using overhead power cables. The resistance of a length of cable may be calculated using the equation shown. length resistance = constant × cross-sectional area One length of an overhead power cable has a resistance of 7.0 Ω. Predict the resistance of a cable that has half the diameter but is the same length. resistance = … Ω [2] (d) The power station uses generators to generate electricity. Fig. 11.1 shows a simple generator. N S slip rings V Fig. 11.1 A voltage is generated when a coil of wire is turned in a magnetic field. The voltage is measured using a voltmeter connected across slip rings as shown in Fig. 11.1. (i) On the grid in Fig. 11.2, sketch a graph of voltage output against time for the generator, when the coil is rotating at constant speed. voltage output time Fig. 11.2 [2] (ii) State one way in which the size of the induced voltage can be increased. … … [1] (e) A generator is very noisy and emits sound waves which pass through the air. The speed of sound waves in air is 340 m / s. The frequency of the sound waves is 490 Hz. (i) Calculate the wavelength of the sound waves. State the formula you use and show your working. formula working wavelength = … m [2] (ii) Fig. 11.3 represents a sound wave travelling through the air from the generator. direction of travel Fig. 11.3 On Fig. 11.3, label a compression with the letter C. [1] (iii) The generator turns faster and the frequency of the sound emitted increases. Suggest how the distance between two compressions changes. … [1]

14 marks

Mark scheme: 11(a) use Geiger counter etc. ; test for absorption by shield of lead / thick aluminium ; γ-rays are more penetrating than α or β / α and β will not penetrate lead ; OR measure deflection by magnetic / electric field ; γ-rays not deflected / α and β deflected ; 3 11(b) U 235 92 ; He 4 2 OR 4 2 α ; 2 11(c) correct working ; 28 (Ω) ; 2 11(d)(i) approx sin wave ; constant amplitude ; 2 11(d)(ii) stronger magnet / spin coil faster / greater number of turns / increased coil area ; 1 11(e)(i) λ = v / f / 340 / 490 ; = 0.69 (m) ; 2 11(e)(ii) compression correctly labelled ; 1 11(e)(iii) decreases / closer together ; 1

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13 (a) Fig. 13.1 shows information which is on the label attached to a washing machine. voltage 240 V frequency 50 Hz power 2.5 kW Fig. 13.1 (i) Show that the current in the washing machine when in use is 10.4 A. State the formula you use and show your working. formula working [2] (ii) The fuse in the electrical supply to the washing machine has to be replaced. The current through the washing machine when in use is 10.4 A. Three fuses with different current ratings are available and shown in the list below. 10 A 13 A 30 A Explain why only the 13 A fuse should be used. … … … [2] (b) Some washing machines have relays in their circuits. Fig. 13.2 shows a simple relay. contacts high-voltage pivot circuit soft iron soft iron solenoid coil low-voltage circuit Fig. 13.2 Suggest why the contacts close when a current passes through the solenoid coil. … … … [2] (c) Fig. 13.3 represents a sound wave travelling through the air from the washing machine. direction of travel Fig. 13.3 (i) On Fig. 13.3, label a compression with the letter C and a rarefaction with the letter R. [2] (ii) On Fig. 13.3, mark one wavelength with a double headed arrow (↔). [1]

9 marks

Mark scheme: 13(a)(i) (2.5 × 1000) / 240 = 10.4 ; 2 13(a)(ii) must be higher than 10.4 / not 10 A fuse, or else it will blow (with normal current) ; not 30 A fuse if there is a fault too much current will pass through / causes damage to washing machine / causes fire ; 2 13(b) electromagnet / magnetic field created around solenoid coil ; soft iron (armature), attracted to magnet / turns, and closes contacts ; 2 13(c)(i) compression correctly labelled ; rarefaction correctly labelled ; 2 13(c)(ii) one wavelength correctly identified ; 1

This question in 0654/42 May/June 2017

9 (a) A boy riding his bicycle is cooled by sweating. Describe, in terms of molecules, how sweating cools his body by evaporation. … … … … … [3] (b) Fig. 9.1 shows a car behind a bicycle at night. Fig. 9.1 A reflector on the back of the bicycle is made from many small red plastic prisms, one of which is shown in Fig. 9.2. A ray of light from the headlamp of the car enters the prism. ray of light from the headlamp of the following car red plastic prism Fig. 9.2 Total internal reflection occurs within the prism. On Fig. 9.2, complete the path taken by the ray of light until it emerges from the prism. [2] (c) The bicycle has a lamp powered by a small generator. The generator turns as the boy pedals and the lamp lights up. Fig. 9.3 shows a simple version of the generator. axle magnet magnet N S slip ring coil brush lamp Fig. 9.3 Describe how the rotating coil causes the lamp to light. … … … … … … [3] (d) The generator produces an alternating voltage. Fig. 9.4 shows how the output voltage of the bicycle generator changes with time. 6.0 4.0 2.0 voltage / V 0 time / s 0.02 0.04 0.06 0.08 0.10 –2.0 –4.0 –6.0 Fig. 9.4 (i) Calculate the frequency of the alternating voltage. Show your working. frequency = … Hz [1] (ii) State the amplitude of the alternating voltage. amplitude = … V [1] (e) A different bicycle has a front lamp, A, and a rear lamp, B, powered by the same battery. Fig. 9.5 shows how the lamps are connected. 12 V A B Fig. 9.5 (i) State the name given to this arrangement of lamps in a circuit. … [1] (ii) Lamp A has a resistance of 5 Ω. The battery has a voltage of 12 V. Calculate the current flowing through lamp A when the switch is closed. State the formula you use and show your working. formula working current = … A [2] (iii) Lamp B has a resistance of 10 Ω. Calculate the combined resistance of the two lamps in this circuit. Show your working. resistance = … Ω [2]

15 marks

Mark scheme: 9(a) fastest moving / most energetic molecules escape ; remainder are slower / have less energy ; energy used taken from surroundings / molecules gain energy from body ; 3 9(b) first 90° reflection correct ; second 90° reflection correct ; 2 9(c) rotation of coil, cuts magnetic field / experiences changing magnetic field ; induces an emf ; current flows through lamp / pd across lamp causes lamp to light ; 3 9(d)(i) frequency = 25 (Hz) ; 1 Question Answer Marks 9(d)(ii) amplitude = 5 (V) ; 1 9(e)(i) parallel ; 1 9(e)(ii) I = V / R or 12 / 5 ; 2.4 (A) ; 2 9(e)(iii) 1 2 1 2 T R R R R R = + or R = 10 / 3 (Ω) ; = 3.3 (Ω) ; 2

This question in 0654/42 Oct/Nov 2017

9 (a) (i) The nuclear fuel used in a power station is plutonium-239. 239 94 Pu decays by α-emission to produce an isotope of uranium. Use the correct nuclide notation to write a symbol equation for this decay process. … … 239 [2] 94Pu … U + … He (ii) Explain why an α-radiation source that has been swallowed is more dangerous to humans than the same source held close to the skin outside the body. … … [1] (b) Electricity is generated in a nuclear power station by nuclear fission. Nuclear fusion occurs in the Sun to release energy. Describe the difference between nuclear fission and nuclear fusion. … … … [2] (c) There is a generator in the power station. Fig. 9.1 shows a simple electrical generator. coil N S a.c. output Fig. 9.1 Electricity is generated when the coil is turned. (i) Describe how turning the coil induces a voltage. … … [1] (ii) Explain why turning the coil induces an alternating voltage. … … [1] (iii) On the grid in Fig. 9.2, sketch a graph of voltage output against time for the generator, when the coil is rotating at constant speed. voltage output time Fig. 9.2 [2]

9 marks

Mark scheme: 9(a)(i) 239 94Pu → 235 4 92 2 U He + U nuclide ; He nuclide ; 2 9(a)(ii) unable to penetrate skin / closer to body cells when inside the body ; 1 9(b) fission is splitting of nuclei ; fusion is joining of nuclei ; 2 9(c)(i) (each side of ) coil cuts magnetic field lines / coil experiences changing magnetic field ; 1 9(c)(ii) (each side of) coil moves upwards and then downwards / changes direction ; 1 9(c)(iii) sinusoidal wave with constant time period ; equal amplitudes ; 2

This question in 0654/41 Oct/Nov 2018

9 A list of metals is shown. aluminium copper iron lead uranium (a) (i) Scientists wear protective aprons when handling radioactive materials. State which metal from the list is used in the aprons to reduce the ionising radiation passing through. … [1] 234 (ii) An isotope of uranium has a nuclide notation 92 U and decays by alpha emission to produce an isotope of thorium. Use the correct nuclide notation to write a symbol equation for this decay process. … … 23492U … Th + … He [2] (b) Fig. 9.1 shows a simplified diagram of a transformer. core output input voltage voltage 6 V secondary primary coil coil 10 turns 5 turns Fig. 9.1 (i) State which metal from the list is used in the core of a transformer. … [1] (ii) State which metal from the list is used in the coils of a transformer. … [1] (iii) Calculate the voltage induced in the secondary coil of the transformer shown in Fig. 9.1. State the formula you use and show your working. formula working output voltage = … V [2] (c) (i) A block of aluminium has a density of 2700 kg / m3. State the two quantities needed to calculate the density of the block. 1 … 2 … [1] (ii) When aluminium melts, energy is required but the temperature remains the same. Explain what is happening in terms of atoms. Use the term latent heat of fusion in your answer. … … … … … [2] (iii) Aluminium has a specific heat capacity of 913 J / (kg°C). State what is meant by this quantity. … … … [1] (iv) An aluminium cable of length 1 km has a resistance of 1.2 Ω. The cable has a cross- sectional area of 25 mm2. Determine the resistance of another aluminium cable of length 1 km that has a cross- sectional area of 50 mm2. resistance = … Ω [1]

12 marks

Mark scheme: 9(a)(i) lead ; 1 9(a)(ii) thorium correct ; helium correct ; 2 9(b)(i) iron ; 1 9(b)(ii) copper ; 1 9(b)(iii) V2 = V1 × N2 / N1 or 6 × 10 / 5 ; = 12 (V) ; 2 Question Answer Marks 9(c)(i) mass and volume ; 1 9(c)(ii) latent heat of fusion is the energy needed ; to overcome forces of attraction between particles ; 2 9(c)(iii) 913 J are / amount of energy, needed to raise the temperature of 1 kg by 1 °C ; 1 9(c)(iv) 0.6 (Ω) ; 1

This question in 0654/42 Oct/Nov 2018

3 (a) Fig. 3.1 shows the speed-time graph for part of a journey made by a train. 25 speed 20 m / s 15 10 5 0 0 100 200 300 400 500 600 time / s Fig. 3.1 (i) Show that the acceleration of the train at 60 s is 0.25 m / s2. State the formula that you use and show your working. formula working acceleration = … m / s2 [2] (ii) The train has a mass of 7.5 × 105 kg. Calculate the resultant force causing an acceleration of 0.25 m / s2. State the formula you use and show your working. formula working force = … N [2] (b) The electric motor in the train operates at 2000 V. The electrical supply to the train is 25 000 V. A transformer is used to reduce the voltage. Complete the sentences about a transformer using words from the list. Each word may be used once, more than once or not at all. copper current iron plastic primary secondary voltage An alternating … passes through the primary coil. This produces a magnetic field that continuously changes direction. The soft … core increases the strength of the magnetic field. The changing magnetic field passes through the secondary coil, inducing a … across the ends of the coil. In order to reduce the 25 000 V supply to 2000 V, the transformer in the train has more turns on the … coil than on the … coil. [3]

7 marks

Mark scheme: 3(a)(i) acceleration = change in speed / time ; 15 / 60 (= 0.25 (m / s2)) ; 2 3(a)(ii) force = mass × acceleration or 7.5 × 105 × 0.25 ; = 1.9 × 105 (N) ; 2 3(b) current iron voltage primary secondary 1 or 2 correct ; 3 or 4 correct ; 5 correct ; 3

This question in 0654/43 Oct/Nov 2018

3 Fig. 3.1 shows a motorcycle with a rear lamp. rear lamp Fig. 3.1 (a) The lamp has a resistance of 30 Ω and is powered by a 12 V battery. (i) Show that the current in the lamp is 0.40 A. [1] (ii) Calculate the power used by the lamp. Show your working. power = … W [2] (iii) Calculate the charge that passes through the lamp in 30 minutes. Show your working. charge = … C [2] (b) The battery is charged by an a.c. generator. Fig. 3.2 shows a simple a.c. generator. N S a.c. output Fig. 3.2 (i) On Fig. 3.2, label the slip rings with the letter R. [1] (ii) On Fig. 3.2, label the coil with the letter C. [1] (iii) On Fig. 3.2, show the direction of the magnetic field with an arrow ( ). [1] (iv) The output is an alternating current. Describe the difference between direct current (d.c.) and alternating current (a.c.). … … … [1] (c) The motorcycle engine is noisy and emits sound waves that pass through the air. The sound waves pass through the air as a series of compressions (C) and rarefactions (R). Fig. 3.3 shows the positions of the compressions and rarefactions as the sound wave passes through the air. C R C R C R C R C R Fig. 3.3 Suggest how and explain why the positions of the compressions and rarefactions change if the pitch of the sound increases. … … … [3]

12 marks

Mark scheme: 3(a)(i) 12/30 = 0.4 (A) ; 1 3(a)(ii) voltage × current or 12 × 0.40 ; = 4.8 (W) ; 2 3(a)(iii) current × time or 0.4 × 30 (× 60) or 0.4 × 1800 ; =720 (C) ; 2 3(b)(i) correct label ; 1 3(b)(ii) correct label ; 1 3(b)(iii) arrow drawn from N to S ; 1 3(b)(iv) direct current goes in one direction / alternating current changes direction ; 1 3(c) higher frequency / more waves produced per second ; shorter wavelength ; compressions and rarefactions get closer together ; 3

This question in 0654/41 May/June 2019

12 (a) Fig. 12.1 shows a large snow tractor used by scientists working in the Arctic region. continuous tracks Fig. 12.1 The snow tractor has large continuous tracks (caterpillar tracks), driven by the wheels. These tracks allow the snow tractor to travel across the soft snow without sinking. A tractor with four ordinary wheels would sink into the soft snow. Use ideas about pressure to explain this difference. … … … [2] (b) The snow tractor has two headlamps. The headlamps emit visible light of several different wavelengths. One of the wavelengths is 5.01 × 10–7 m. The frequency of this light is 5.98 × 1014 Hz. Calculate the speed of this light. Show your working. speed of light = … m / s [2] (c) Visible light is part of the electromagnetic spectrum. All electromagnetic waves travel at the same speed in a vacuum. State one other property that is the same for all electromagnetic waves. … … [1] (d) Fig. 12.2 shows equipment for measuring wind speed used by Arctic scientists. plastic cups plastic spindle plastic frame coil iron rod V Fig. 12.2 The wind makes the plastic cups move and this causes the spindle and magnet to turn. Suggest why an alternating voltage is measured on the voltmeter. … … … … [3] [Total: 8]

8 marks

Mark scheme: 12(a) tracks spread weight over larger (surface) area ; so pressure is less ; 2 12(b) (v) = f × λ or 5.98 × 1014 × 5.01 × 10-7 ; = 3.00 × 108 (m) ; 2 12(c) all transverse waves ; 1 12(d) (coil experiences) changing magnetic field ; (changing magnetic field) induces emf ; direction of emf changes every half turn ; max 3

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12 (a) Fig. 12.1 shows a gardener using a leaf-blower. Fig. 12.1 Fig. 12.2 shows the energy input and outputs for the leaf-blower. useful total energy energy output input wasted energy output Fig. 12.2 Calculate the efficiency of the leaf-blower as a percentage. Show your working. efficiency = … % [2] (b) When used the leaf-blower takes a current of 3.0 A. Calculate the charge that flows through the leaf-blower when it is used for 180 seconds. Show your working. charge = … C [1] (c) The leaf-blower contains a small electric motor powered by a battery. Fig. 12.3 shows a simple electric motor powered by a battery. coil N S electric current Q Fig. 12.3 (i) State the name of the component labelled Q on Fig. 12.3. name of component Q … [1] (ii) Draw an arrow on Fig. 12.3 to show the direction of the magnetic field. [1] (iii) Explain why the coil moves when an electric current passes through it. … … … … [3] [Total: 8]

8 marks

Mark scheme: 12(a) = 37.5% ; 2 12(b) (charge = current x time = 3 × 180 =) 540 (C) ; 1 12(c)(i) split ring commutator ; 1 12(c)(ii) arrow from N pole to S pole ; 1 12(c)(iii) current produces magnetic field (around coil) ; magnetic field interacts with other magnetic field ; force exerted (on current carrying conductor in magnetic field) ; 3

This question in 0654/43 May/June 2019

12 (a) Ultrasound is very high frequency sound. A submarine uses ultrasound to determine the distance to the sea bed. Pulses of ultrasound are sent out through the water. The ultrasound pulses reflect off the sea bed and are detected in the submarine 1.2 seconds later. Ultrasound waves travel through water at a speed of 1500 m / s. (i) Calculate the distance of the sea bed below the submarine. distance = … m [2] (ii) The wavelength of ultrasound is 5 cm. Show that the frequency of the ultrasound is 30 000 Hz. [2] (iii) Ultrasound waves travel as a series of compressions and rarefactions. Fig. 12.1 shows the positions of some compressions and rarefactions of an ultrasound wave. Fig. 12.1 On Fig. 12.1 label a compression with the letter C and a rarefaction with the letter R. [1] (b) Submarines use periscopes to view ships on the surface of the sea. Fig. 12.2 shows an incomplete simple periscope. ship periscope observer looking at object Fig. 12.2 On Fig. 12.2, draw: • two plane mirrors in position so that a ray of light from the ship passing through the periscope will be reflected by both mirrors to the observer’s eye • the path of this ray of light from the ship, through the periscope, to the observer’s eye. [3] (c) The submarine has a generator to generate electricity. Fig. 12.3 shows a simple generator. coil N S Z a.c. output Fig. 12.3 (i) Name the parts of the generator labelled Z on Fig. 12.3. … [1] (ii) Explain why a rotating-coil generator produces an alternating current. … … … … [3] [Total: 12]

12 marks

Mark scheme: 12(a)(i) depth = 1800 / 2 = 900 (m) ; 2 12(a)(ii) 0.05 (m) OR 150 000 (cm / s) ; (f = ) 1500 / 0.05 OR 150 000 / 5 ; ( = 30 000 Hz) 2 12(a)(iii) compression and rarefaction correctly identified ; 1 12(b) two mirrors in correct places ; two plane mirrors in correct places and correct orientations ; correct reflections shown ; 3 12(c)(i) slip rings ; 1 12(c)(ii) coil cuts lines of magnetic field / coil moves in magnetic field / coil experiences changing magnetic field ; e.m.f. / current induced ; each side of coil moves upwards and then downwards (through field as it turns) owtte ; current changes direction every half turn / flows in one direction and then the other ; max 3 3

This question in 0654/41 Oct/Nov 2019

12 A fishing boat floats on the sea. (a) A heavy anchor is dropped from the boat and accelerates as it falls through the water to the sea bed. Name the downward force that makes the anchor accelerate. … [1] (b) The boat has a small generator to generate electricity. Fig. 12.1 shows a simple generator. N S Fig. 12.1 (i) On Fig. 12.1 label a slip ring with the letter R. [1] (ii) Describe how the use of slip rings produces an alternating voltage output from the rotating coil. … … … [2] (iii) On the grid in Fig. 12.2, sketch a graph of voltage output against time for the generator, when the coil is rotating at a constant speed. voltage output time Fig. 12.2 [2] (c) An electric heater on the boat uses the electricity generated at 240 V. The current passing through the heater is 20 A. Calculate the charge passing through the heater in one hour. State the unit of your answer. charge = … unit … [3] (d) A fisherman on the boat is using a pair of binoculars to look at the sea. Binoculars use glass prisms to reflect light. Fig. 12.3 shows part of a pair of binoculars. A ray of light is shown entering and leaving. glass prism light ray entering light ray leaving Fig. 12.3 On Fig. 12.3, complete the ray diagram to show the path of the light ray through the two prisms. [1] [Total: 10]

10 marks

Mark scheme: 12(a) weight ; 1 12(b)(i) slip rings labelled correctly ; 1 12(b)(ii) induced voltage changes every half turn ; same side of coil remains connected to same slip ring ; 2 12(b)(iii) approx. sine curve ; regular frequency and amplitude ; 2 12(c) (charge =) current × time or 20 × 1 × 60 × 60 ; 72 000 ; C ; 3 12(d) ray drawn correctly through first prism and through second prism ; 1

This question in 0654/42 Oct/Nov 2019

3 (a) Fig. 3.1 shows a bar magnet suspended by a spring above a coil that is connected to a voltmeter. spring magnet N coil S voltmeter V Fig. 3.1 When the magnet is pulled downwards into the coil and then released, it oscillates up and down inside the coil. An alternating voltage is observed on the voltmeter. Explain why an alternating voltage is observed. … … … [2] (b) A thin piece of iron wire has a diameter of 0.20 mm. (i) Name the device which could accurately measure very small distances such as 0.20 mm. … [1] (ii) The wire is 0.10 m in length and has a resistance of 0.30 Ω. Determine the resistance of a piece of wire made from the same iron metal that is 0.10 m in length but has a diameter of 0.40 mm. resistance = … Ω [2] (c) The isotope iron-55 has a half-life of 2.7 years. A sample of this isotope contains 8 × 1012 atoms. Some time later 7 × 1012 atoms have decayed. Calculate the time needed for this number of atoms to decay. time = … years [3] (d) Fig. 3.2 shows an iron rod being heated at one end by a Bunsen burner. Fig. 3.2 Thermal energy passes through the rod by conduction. (i) Describe the process of conduction in solid iron, using ideas about the vibration of atoms. … … … … [2] (ii) When heated, the iron rod expands. Explain in terms of the motion and arrangement of the atoms why iron expands when heated. … … … [2] [Total: 12]

12 marks

Mark scheme: 3(a) voltage induced as coil cuts magnetic field / induced as magnetic field in coil changes ; voltage reverses when magnet changes direction ; 2 3(b)(i) micrometer screw gauge ; 1 3(b)(ii) doubling diameter quadruples CSA / evidence of dividing by 4 ; 0.075 (Ω) ; 2 3(c) 1 × 1012 atoms undecayed ; 3 half-lives ; (3 × 2.7) = 8.1 (years) ; 3 3(d)(i) (incident energy / energy gained, makes) atoms vibrate more ; this vibration is passed through metal ; 2 3(d)(ii) atoms have greater (amplitude of) vibration ; about a fixed point so take up more space / (average) distance between particles increases / owtte ; 2

This question in 0654/43 Oct/Nov 2019

6 (a) Describe how thermal energy passes through copper by conduction. … … … … [2] (b) Copper boils at 2562 °C. Describe two differences between boiling and evaporation. 1 … … 2 … … [2] (c) Equal volumes of air, copper and water are heated from 10 °C to 90 °C. State which of these materials will expand: most … least. … [1] (d) A copper wire of length 0.5 m has a resistance of 0.02 Ω. Determine the resistance of another copper wire of length 0.25 m that has twice the cross- sectional area. resistance = … Ω [2] (e) Two wires are connected in parallel. One wire has a resistance of 0.40 Ω. The other wire has a resistance of 0.60 Ω. Calculate the combined resistance of the two wires connected together in parallel. resistance = … Ω [2] (f) Copper wire is used in the coil of a generator. Fig. 6.1 shows a simple a.c. generator. Fig. 6.1 (i) On Fig. 6.1 label the coil with the letter C. [1] (ii) An electromotive force (e.m.f.) is induced in the rotating coil. State two factors that would increase the magnitude of the induced e.m.f. 1 … 2 … [2] [Total: 12]

12 marks

Mark scheme: 6(a) thermal energy transferred as (vibrational) energy of atoms ; vibrations passed from atom to atom ; delocalised electrons transfer energy ; max 2 Question Answer Marks 6(b) evaporation can occur at any temperature / boiling occurs at the boiling point; evaporation happens only at the surface / boiling occurs throughout the liquid; during boiling all / most moleculaes have enough energy to leave / evaporation only lets the molecules with the greatest kinetic energy escape; evaporation can occur using the internal energy of the system / boiling requires a(n external) source of heat; evaporation is a slow process / boiling is a rapid process; evaporation produces cooling / boiling does not produce cooling; max 2 6(c) most – air and least copper ; 1 6(d) evidence of division by 2 twice; 0.005 (Ω) ; 2 6(e) 1/RT = 1/R1 + 1/R2 or RT = R1 R2 /R1 + R2 or correct substitution; 0.24 (Ω) ; 2 6(f)(i) coil labelled correctly; 1 6(f)(ii) rotate coil faster ; increase magnetic field strength ; 2

This question in 0654/41 May/June 2020

6 The nuclear fuel used in some power stations is plutonium-239. (a) (i) Plutonium-239 decays by α-particle emission. Use nuclide notation to complete the symbol equation for this decay process. 23994Pu [3] (ii) Plutonium-239 has a half-life of 24 000 years. 2 kg of plutonium-239 is sealed in a lead container. Calculate the mass of plutonium-239 remaining after 120 000 years. mass = … kg [2] (b) The nuclear fuel releases 8.6 × 1013 J of energy. From this, only 3.2 × 1013 J of electrical energy is generated. Calculate the efficiency of this generation process. efficiency = … % [2] (c) The power station generates electricity at 25 000 V. A transformer increases this voltage to 400 000 V before the electricity is transmitted over large distances through transmission cables. The number of turns on the secondary coil of the transformer is 500 000. Calculate the number of turns on the primary coil of the transformer. number of turns = … [2] (d) When electricity has been generated at the power station the voltage is increased by a transformer to reduce power losses in the transmission cables. Explain why power losses in cables are lower when the voltage is high. … … … … [2] [Total: 11]

11 marks

Mark scheme: 6(a)(i) uranium identified; 235 and 92; helium notation correct; 3 6(a)(ii) five half-lives; 0.0625 (kg); 2 6(b) formula or correct substitution; 37(%) 2 6(c) V1/V2 = N1/N2 or correct substitution; 62 500 ; 2 6(d) higher voltage means lower current; power loss increases with current / power loss is I2R; 2

This question in 0654/42 May/June 2020

12 (a) Fig. 12.1 shows a laptop computer and charger. charger laptop Fig. 12.1 The charger contains a transformer. The input voltage across the primary coil is 250 V. The primary coil has 5000 turns. The output voltage from the secondary coil is 19 V. (i) Explain why this transformer is called a step‑down transformer. … … [1] (ii) Calculate the number of turns on the secondary coil. number of turns = … [2] (b) The laptop computer has a rechargeable battery. The battery takes 2 hours to charge fully when a voltage of 19 V is used with a current of 1.1 A. Calculate the energy transferred during the 2 hours. energy = … J [3] (c) Fig. 12.2 shows the laptop computer being closed by a force of 12 N. 12 N 24 cm pivot Fig. 12.2 Calculate the moment of the force about the pivot. moment = … N m [2] (d) The microprocessor in the laptop generates large quantities of thermal energy. The thermal energy must be removed so that the microprocessor does not overheat. Fig. 12.3 shows a heat sink placed in contact with the microprocessor. black metal fins heat sink microprocessor Fig. 12.3 Thermal energy is conducted from the microprocessor into the metal fins of the heat sink. Suggest and explain two ways in which the design of the heat sink allows thermal energy to be removed efficiently from the heat sink. 1 … … 2 … … [2] [Total: 10]

10 marks

Mark scheme: 12(a)(i) voltage is lowered ; 1 12(a)(ii) (NS =) NPVS/VP or 5000 × 19/250 ; number of coils = 380 ; 2 12(b) 2 hours = 2 × 3600 = 7200 s; (energy =) VIt / 19 × 1.1 × 7200 ; (energy =) 150 000 (J) ; 3 12(c) (moment =) force × (perpendicular) distance or 12 × 24(/100) ; 2.9 (Nm) ; 2 Question Answer Marks 12(d) black surfaces are good emitters of thermal energy ; large surface area enables efficient convection; 2

This question in 0654/41 Oct/Nov 2020

12 (a) Fig. 12.1 shows a truck crossing a bridge. Fig. 12.1 The bridge is designed with gaps in the road surface as shown in Fig. 12.2. road surface metal strip gaps Fig. 12.2 The temperature of the road surface increases on a hot day. (i) Describe what happens to the gaps in the road surface when the temperature increases. Explain your answer. … … … [2] (ii) Suggest what may happen to the bridge if there were no gaps in the road surface. … … [1] (b) Fig. 12.3 shows the fuel tank of the truck being filled with diesel fuel. – – – – – – – + + – + + + + + + + + + + ++ + delivery diesel pipe fuel fuel tank Fig. 12.3 Explain why the diesel fuel becomes positively charged. … … … [2] (c) The truck has a warning triangle to alert other drivers. Fig. 12.4 shows the warning triangle. Fig. 12.4 Many tiny prisms are contained in the warning triangle. Fig. 12.5 shows one ray of light entering a prism. Fig. 12.5 The ray undergoes total internal reflection inside the prism. Complete Fig. 12.5 to show the path of the ray of light through the prism and the ray of light leaving the prism. [2] (d) The truck has a generator. Fig. 12.6 shows a simple generator producing an alternating voltage. Fig. 12.6 (i) On Fig. 12.6, label the coil C. [1] (ii) On Fig. 12.6, label the slip rings S. [1] (iii) Describe how turning the coil induces an alternating voltage. … … … … [3] [Total: 12]

12 marks

Mark scheme: 12(a)(i) gap closes ; road expands in the heat ; 2 12(a)(ii) (the road will) buckle / bend / break / be damaged ; 1 Question Answer Marks 12(b) ref to friction / described ; transfer of electrons ; from the fuel (to the pipe) ; max 2 2 12(c) reflection only shown at first reflection ; after second reflection ray emerges parallel to incident ray ; 2 12(d)(i) coil correctly labelled ; 1 12(d)(ii) slip rings correctly labelled ; 1 12(d)(iii) magnetic field ; rotating coil cuts magnetic field or flux / experiences a changing magnetic field ; e.m.f. / current reverses every half turn ; 3

This question in 0654/42 Oct/Nov 2020

12 (a) Fig. 12.1 shows a hot water storage tank in a house. hot water outlet tank water electric cold water heater inlet Fig. 12.1 The water is heated by an electric heater placed near the bottom of the tank. Cold water enters at the bottom of the tank and hot water leaves at the top of the tank. Explain why all the water in the tank is heated by convection. … … … … [3] (b) The house is fitted with a smoke detector. The smoke detector contains a radioactive isotope of americium-241. Americium-241 decays by α-particle emission. (i) Explain why it is safe to use this isotope of americium near people in the house. … … [1] (ii) Use nuclide notation to complete the symbol equation for the α-decay process. 241 … … Am Np + … 95 … … [4] (c) There is a rechargeable electric toothbrush in the bathroom of the house. Fig. 12.2 shows the electric toothbrush and the charger. Fig. 12.2 In the charger, there is a transformer that steps down the voltage from 220 V to 2.4 V. The primary coil of the transformer has 5000 turns. Calculate the number of turns on the secondary coil. number of turns = … [2] [Total: 10]

10 marks

Mark scheme: 12(a) hot water is less dense / expands ; less dense water rises ORA ; cold water sinks ; 3 12(b)(i) alpha particles have low penetration; 1 12(b)(ii) 241 95 Au → + 237 4 93 2 He Np mass numbers and proton numbers correct: 237 ; 93 ; 4 ; 2He ; 4 12(c) (NS =) NPVS / VP or 5000 x 2.4 / 220 ; 54.5 / 54 / 55 turns; 2

This question in 0654/43 Oct/Nov 2020

6 (a) Electricity may be obtained using the sources listed. fossil fuels geothermal solar tidal wind (i) State which of the sources of energy is non-renewable. … [1] (ii) State which two of the sources of energy are not dependent on the Sun. … and … .[1] (b) Many types of power station use steam to turn a turbine attached to a generator. Explain, in terms of the forces and distances between molecules and the motion of molecules, why steam is able to fill its container. … … … … … … [3] (c) Fig. 6.1 shows a diagram of a simple a.c. generator. coil N S a.c. output Fig. 6.1 (i) Explain why the generator produces an a.c. output. … … … … … … [3] (ii) On the grid provided in Fig. 6.2, sketch a graph of voltage output against time for this generator. You must show at least one full cycle. voltage output 0 time Fig. 6.2 [1] [Total: 9]

9 marks

Mark scheme: 6(a)(i) fossil fuels ; 1 6(a)(ii) geothermal and tidal ; 1 6(b) any three from: particles are free to move / particle movement is random ; rapid movement of particles / high kinetic energy of particles ; particles are far apart / low particle density ; forces between molecules are, weak / zero ; 3 Question Answer Marks 6(c)(i) any two from: the coil turns ; in a magnetic field / cuts a magnetic field / experiences a changing magnetic flux ; induces emf ; plus: changes direction every half turn ; 3 6(c)(ii) sine wave ; 1

This question in 0654/42 Feb/March 2021

3 Fig. 3.1 shows a circuit used by a student to investigate the resistance of a metal wire. A wire V Fig. 3.1 (a) Suggest why a fixed resistor has been included in the circuit. … … [1] (b) When the switch is closed, the voltmeter reads 1.2 V and the ammeter reads 0.40 A. (i) Calculate the resistance of the wire. resistance = … Ω [2] (ii) Calculate the amount of energy dissipated by the wire in 15 seconds. State the unit of your answer. energy = … unit = … [3] (iii) State the energy transfer happening in the wire as current passes through it. from … energy to … energy [1] (c) The wire is replaced with a second wire made of the same metal and of the same length but with twice the cross‑sectional area. Determine the resistance of the second wire. resistance = … Ω [1] (d) The student wants to calculate the cross‑sectional area of the wire. State the quantity the student needs to measure and suggest a suitable measuring instrument to use. quantity … measuring instrument … [2] (e) Fig. 3.2 shows the wire being placed in between the poles of a permanent magnet. This causes a force to act on the wire. N direction of current S Fig. 3.2 (i) Draw an arrow on Fig. 3.2 to show the direction of the force acting on the wire. [1] (ii) State two ways to increase the size of the force acting on the wire. 1 … … 2 … … [2] [Total: 13]

13 marks

Mark scheme: 3(a) to reduce the potential difference across wire / to reduce the current through the wire / to stop wire melting / heating ; 1 3(b)(i) R = V / I or 1.2 / 0.40 ; 3.0 (Ω) ; 2 3(b)(ii) (E=) VIt or 0.40x1.2x15 ; 7.2 ; joules / J ; 3 3(b)(iii) electrical and thermal ; 1 3(c) 1.5 (Ω) ; 1 3(d) measure the diameter ; use a micrometer screw gauge ; 2 3(e)(i) downwards arrow ; 1 3(e)(ii) increase current ; increase strength of the magnetic field ; 2

This question in 0654/41 May/June 2021

9 (a) Fig. 9.1 represents a straight piece of wire carrying a current passing through a sheet of paper. direction of current Fig. 9.1 (i) On Fig. 9.1, draw two field lines to show the shape and direction of the magnetic field around the wire. [2] (ii) State what effect reversing the direction of the current would have on the magnetic field. … … [1] (b) Fig. 9.2 shows the wire placed into the magnetic field of a permanent magnet. N direction of current S Fig. 9.2 (i) State the direction of the force acting on the wire. … [1] (ii) Suggest two changes that would increase the size of the force acting on the wire. 1 … … 2 … … (c) Fig. 9.3 shows an electric motor. N S _ + Fig. 9.3 (i) The following statements explain what causes the coil in Fig. 9.3 to rotate. The statements are in the wrong order. A A current flows through the coil. B The coil experiences a force and starts to spin. C The power supply applies a potential difference across the coil. D This causes a magnetic field to be induced around the coil. E This interacts with the permanent magnetic field. Arrange the statements into the correct order. C B [2] (ii) On Fig 9.3, label the split-ring commutator with a cross (X). [1] (iii) Describe how the split-ring commutator allows the coil to keep on turning. … … [1] (d) A simple a.c. generator produces an alternating voltage. Fig 9.4 shows how the voltage from the generator varies with time in the form of a wave. voltage time Fig. 9.4 (i) On Fig. 9.4, draw a double headed arrow ( ) to show the time taken for the coil in the generator to complete one full rotation. [1] (ii) The size of the voltage from the generator is indicated by the amplitude of the wave in Fig. 9.4. On Fig. 9.4, draw the voltage output of the generator with a smaller voltage. [1] [Total: 12]

12 marks

Mark scheme: 9(a)(i) concentric circles ; anticlockwise ; 2 9(a)(ii) direction would reverse / it would be clockwise ; 1 9(b)(i) up ; 1 9(b)(ii) increasing the current ; increasing the strength of the magnetic field ; 2 9(c)(i) A – D – E ;; 2 9(c)(ii) split-ring commutator correctly labelled ; 1 9(c)(iii) reverses the direction of the current (every half turn) ; 1 9(d)(i) time period correctly labelled ; 1 Question Answer Marks 9(d)(ii) sine wave drawn with smaller amplitude ; 1

This question in 0654/43 May/June 2021

12 Fig. 12.1 shows a transformer. X 10 V a.c. V voltmeter power supply primary coil secondary coil Fig. 12.1 (a) (i) State the name of the component labelled X. … [1] (ii) Suggest a suitable material for making component X. … [1] (b) There are 5 turns on the primary coil and 30 on the secondary coil. (i) Calculate the reading on the voltmeter. voltage = … V [2] (ii) Suggest two ways to increase the reading on the voltmeter. 1 … 2 … [2] (c) The following statements explain how the transformer produces a reading on the voltmeter. The statements are in the wrong order. A. An alternating potential difference is applied to the primary coil. B. The secondary coil experiences a changing magnetic field. C. This produces a changing magnetic field in the primary coil. D. An alternating current flows in the primary coil. E. This produces an alternating potential difference across the voltmeter. Arrange the statements into the correct order. The first and last steps have been done for you. A E [2] (d) The transformer has an efficiency of 95%. Describe what is meant by an efficiency of 95%. … … [1] [Total: 9]

9 marks

Mark scheme: 12(a)(i) core ; 1 12(a)(ii) (soft) iron ; 1 12(b)(i) (Vs =) Vp × Ns ÷ Np or 10 × 30÷ 5 ; 60 (V) ; 2 12(b)(ii) increase secondary turns ; decrease primary turns ; increase primary voltage ; max 2 12(c) (A) D C B (E) ;; 2 12(d) 95% of the input power / energy is transferred to useful output / 5% of the input power / energy is wasted ; 1

This question in 0654/41 Oct/Nov 2021

12 (a) Fig. 12.1 shows a transformer. a.c. power supply V Fig. 12.1 (i) On Fig. 12.1, label the soft‑iron core with an X. [1] (ii) The transformer has 17 turns on the primary coil and 8 turns on the secondary coil. Calculate the output voltage when the a.c. power supply has an e.m.f. of 34 000 V. Assume the transformer has an efficiency of 100%. output voltage = … V [2] (b) Fig. 12.2 shows a current‑carrying solenoid. I I Fig. 12.2 On Fig. 12.2, draw the magnetic field pattern, including direction, around the solenoid. [2] (c) The radioactive isotope uranium‑238 decays into an isotope of thorium by emitting an α‑particle. (i) Use the correct nuclide notation to complete the decay equation for uranium‑238. 238 … … 92 U … Th + … α [2] (ii) Suggest why an α‑particle is deflected when moving through a magnetic field. … … … … [2] [Total: 9]

9 marks

Mark scheme: 12(a)(i) soft-iron core correctly labelled ; 1 12(a)(ii) use of Vp / Vs =Np / Ns ; 16 000 (V) ; 2 12(b) ;; 2 12(c)(i) ;; 2 Question Answer Marks 12(c)(ii) (alpha particle is) charged ; so experiences a force ; 2

This question in 0654/42 May/June 2022

12 Fig. 12.1 shows a forklift truck lifting a crate. crate height = 2.2 m Fig. 12.1 (a) The forklift truck does 2750 J of work on the crate when the crate is lifted through a height of 2.2 m. The gravitational field strength, g, is 10 N / kg. Calculate the mass of the crate. mass = … kg [2] (b) Fig. 12.2 shows the same forklift truck after it has lowered the crate. crate Fig. 12.2 Explain why the forklift truck is more stable after it has lowered the crate. Use ideas about centre of mass in your answer. … … [1] (c) The forklift truck uses an electric motor to lift the crate. Fig. 12.3 shows a simple d.c. motor. coil Y N X Z S – + Fig. 12.3 (i) A current flows through the coil. Draw arrows on Fig. 12.3 to show the direction of the force acting on points X and Z on the coil. [1] (ii) State why point Y does not experience a force. … … [1] (d) A β-particle passes between the poles of a permanent magnet. (i) Suggest why a β-particle is deflected when moving through a magnetic field. … … … … [2] (ii) State and explain how the deflection direction of an α-particle would differ from that of the β-particle. … … … … [2]

9 marks

Mark scheme: 12(a) (m =) W / gh OR  2750 10 2.2 ; 125 (kg) ; 2 12(b) lower centre of mass ; 1 12(c)(i) X arrow pointing up AND Z arrow pointing down ; 1 12(c)(ii) the current is parallel to the magnetic field ; 1 12(d)(i) experiences a force ; it is a charged particle ; 2 Question Answer Marks 12(d)(ii) opposite direction ; because the charge is opposite /  is positive and  is negative ; OR less deflection ; due to (much) larger mass ; max 2 2

This question in 0654/43 May/June 2022

3 Fig. 3.1 shows a crane lifting a wooden crate. pivot 5.0 m crate 1200 N counterweight Fig. 3.1 (a) The crane is in equilibrium. (i) The 1200 N counterweight is 5.0 m away from the pivot. Calculate the moment of the counterweight about the pivot. moment = … Nm [2] (ii) Determine the moment of the crate about the pivot. moment = … Nm [1] (b) The crate gains 105 kJ of gravitational potential energy as it is lifted through a height of 42 m. Calculate the mass of the crate. The gravitational field strength, g, is 10 N / kg. mass = … kg [2] (c) The crane uses an electric motor. Fig. 3.2 shows a simple d.c. motor. coil rotates clockwise force N S Q _ + force metal or graphite brush contact Fig. 3.2 (i) State the name of the component labelled Q in Fig. 3.2. … [1] (ii) Draw an arrow on Fig. 3.2 to show the direction of the magnetic field. [1] (iii) State two ways to increase the speed at which the coil rotates. 1 … … 2 … … [2] [Total: 9]

9 marks

Mark scheme: 3(a)(i) (M =) F  d OR 1200  5 ; 2 (M =) 6000 (Nm) ; 3(a)(ii) 6000 ; 1 3(b) (m =) GPE / (gh) or 105000/(42  10) or 105000 / 420 ; 2 (m =) 250 (kg) ; 3(c)(i) split–ring commutator ; 1 3(c)(ii) arrow drawn N to S ; 1 3(c)(iii) any two from: 2 increase the current ; increase magnetic field strength ; increase number of turns on the coil ;

This question in 0654/41 Oct/Nov 2022

9 Burning coal can be used to generate electricity. (a) State one advantage and one disadvantage of using coal to generate electricity. advantage … … disadvantage … … [2] (b) The thermal energy released by the coal is used to turn liquid water into steam. (i) Compare the: • forces between molecules • distances between molecules • motions of molecules in a liquid at 100 °C and a gas at 100 °C. forces between molecules … distances between molecules … motions of molecules … … [3] (ii) Complete Table 9.1 to describe what happens to the pressure in a sample of steam under different conditions. Assume the steam remains as a gas under each set of conditions. Use the words increases, decreases or remains constant. You can use each word once, more than once or not at all. Table 9.1 temperature volume pressure increases remains constant decreases remains constant remains constant increases remains constant decreases [2] (c) A transformer is used to change the potential difference of the output from a coal-fired power station. The transformer is made up of a primary coil and a secondary coil, wrapped around an iron core. (i) The potential difference across the primary coil is 20 kV. The primary coil contains 120 turns. The potential difference across the secondary coil is 400 kV. Calculate the number of turns on the secondary coil. number of turns = … [2] (ii) The electric power is transported from the power station over large distances at 400 kV. This is a very high potential difference. Explain why a very high potential difference is used. … … … … … [2] [Total: 11]

11 marks

Mark scheme: 9(a) (advantage) 2 high energy density / fast start up of power stations / abundant / easily available / easy to transport or store / reliable / easily combustible / AVP ; (disadvantage) releases CO2 / causes global warming / climate change / finite or non-renewable resource / releases SO2 / causes acid rain / pollution from particulates / AVP ; 9(b)(i) (forces) stronger in liquid / ORA ; 3 (distance) closer in liquid / ORA ; (motion) molecules are freer to move in gas / ORA ; 9(b)(ii) increases 2 decreases ; decreases increases ; 9(c)(i) use of Vp / Vs = Np / Ns ; 2 2400 ; 9(c)(ii) reduces current ; 2 reduces, power or energy losses / less heat generated ;

This question in 0654/42 Oct/Nov 2022

12 Fig. 12.1 shows a wire being moved between the poles of a magnet. The wire is connected to an ammeter which measures the current induced in the wire as the wire is moved. When the wire moves from left to right the ammeter shows a positive reading. movement of wire S A N Fig. 12.1 (a) (i) Explain why a current is induced in the wire as it is moved between the poles of the magnet. … … … … [2] (ii) Place ticks (3) in Table 12.1 to show how the reading on the ammeter changes under different conditions. Table 12.1 ammeter reading the wire in (a)(i) is: becomes zero increases decreases becomes negative moved faster moved from right to left kept stationary replaced with a wire of lower resistance [2] (b) A magnet is used to investigate the behaviour of ionising radiation. (i) Fig. 12.2 shows the paths taken by three types of ionising radiation as they pass through a magnetic field. alpha S P Q N Fig. 12.2 The path taken by an alpha particle has been labelled for you. State the types of radiation which would follow the paths labelled P and Q. P … Q … [1] (ii) When americium‑241 (24195 Am) decays it emits an alpha particle. Use the correct nuclide notation to complete the decay equation for americium‑241. 241 Am … Np + … α 95 93 … [2] (iii) Americium‑241 is a source of alpha particles. It is used in smoke detectors. Fig. 12.3 shows part of the inside of a smoke detector. The alpha particles cause a current in the sensor. When the detector fills with smoke, a change in current is detected by a sensor which sounds an alarm. alarm circuit source of alpha particles Am sensor path of alpha particles lead shield Fig. 12.3 Suggest two reasons why a source of alpha particles is used and not any other type of ionising radiation. 1 … … 2 … … [2] [Total: 9]

9 marks

Mark scheme: 12(a)(i) the wire experiences a changing magnetic field ; 2 an emf is induced in the wire ; 12(a)(ii) 2 ammeter reading the wire in (a)(i) is: becomes zero increases decreases becomes negative moved faster ✓ moved right to left ✓ kept stationary ✓ replaced with a wire with a lower ✓ resistance ;; 12(b)(i) (P:) beta AND 1 (Q:) gamma ; 12(b)(ii) 2 ;; 12(b)(iii) least penetrating / short range ; 2 easily stopped by smoke ; AVP ;

This question in 0654/42 Feb/March 2023

9 A student investigates how the resistance of a wire changes with length. Fig. 9.1 shows the equipment she uses. cell ammeter 0.66 1.5 V wire ruler crocodile clips Fig. 9.1 (a) The student moves the crocodile clips to change the length of the wire. She measures this length with the ruler and uses the ammeter reading to calculate the resistance of the wire. When the wire is made longer, the reading on the ammeter decreases. Explain why the reading on the ammeter decreases. … … … … [2] (b) Fig. 9.2 shows a length of wire connected in series with another component labelled X. 1.5 V A wire X V Fig. 9.2 (i) State the name of the component labelled X in Fig. 9.2. … [1] (ii) The student uses the component labelled X to vary the potential difference across the length of wire. The student records the potential difference across the wire and the current in the wire. Fig. 9.3 shows her results. 1.75 1.50 1.25 1.00 potential difference / V 0.75 0.50 0.25 0 0 0.20 0.40 0.60 0.80 current / A Fig. 9.3 Use Fig. 9.3 to determine the resistance of the wire. resistance = … Ω [2] (c) The student chooses to use a maximum electromotive force (e.m.f.) of 1.5 V. State the meaning of the term electromotive force (e.m.f.). … … [2] (d) On Fig. 9.4, draw the shape and direction of the magnetic field around the current‑carrying wire. direction of current Fig. 9.4 [2] [Total: 9]

9 marks

Mark scheme: 9(a) (as length increases) resistance increases ; (as resistance increase) current decreases / resistance inversely proportional to resistance ; 2 9(b)(i) variable resistor ; 1 9(b)(ii) (resistance = ) V / I / 1.50/ 0.80 ; (resistance = ) 1.9 () ; 2 9(c) energy supplied / (electrical) work done (by a source) ; driving charge around a (complete) circuit / per (unit) charge around a (complete) circuit ; 2 9(d) concentric circle(s) around wire ; direction shown anti-clockwise ; 2

This question in 0654/41 May/June 2023

6 (a) Fig. 6.1 shows the average power output over a summer’s day from a solar panel made from solar cells. 4.0 3.5 3.0 2.5 power output / kW 2.0 1.5 1.0 0.5 0.0 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 time of day Fig. 6.1 (i) State the time at which the power output of the solar panel is at its maximum. time of day … [1] (ii) Suggest one reason why the power output of the solar panel is at a maximum at this time. … … [1] (b) Table 6.1 gives some data about different types of power stations. Table 6.1 power station fuel efficiency output voltage output power / % / kV / MW P coal 30 22 1500 Q natural gas 40 31 1000 R uranium 30 23 1300 Use Table 6.1 to complete each sentence. Each letter, P, Q or R, can be used once, more than once or not at all. The power station that produces the least carbon dioxide is power station … . The power station that releases the most energy per second is power station … . The power station with the generator that produces the largest current is power station … . [2] (c) Power stations use transformers to increase the output voltage. Fig. 6.2 shows a simple transformer. X input voltage output voltage secondary coil primary coil Fig. 6.2 (i) State the name of the part of the transformer labelled X. … [1] (ii) Describe how the output voltage across the secondary coil is produced. … … … … … … [3] (iii) Fig. 6.2 shows a step‑up transformer containing 8 turns in the primary coil and 17 turns in the secondary coil. The input voltage across the primary coil is 22 kV. Calculate the output voltage across the secondary coil. output voltage = … kV [2] [Total: 10]

10 marks

Mark scheme: 6(a)(i) 12:00 ; 1 6(a)(ii) the light is incident at (almost) 90° / ref to maximum light intensity / the sun is highest in the sky / directly above the solar panel / AVP ; 1 6(b) R P P ;; 2 6(c)(i) (soft-iron) core ; 1 6(c)(ii) alternating / changing, current / voltage, in primary coil ; produces a, changing / alternating, magnetic field (in the soft-iron core) ; which induces an, (alternating) voltage / emf / potential difference (in the secondary coil) ; 3 6(c)(iii) (Vs =) Vp  Ns / Np or 22  17 / 8 ; (Vs =) 47 (kV) ; 2

This question in 0654/42 May/June 2023

6 Fig. 6.1 shows wind turbines used to generate electricity. Fig. 6.1 (a) Fig. 6.2 shows how the power output of one wind turbine changes with wind speed. 350 300 250 power output 200 / kW 150 100 50 0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 wind speed m / s Fig. 6.2 On one particular day, the wind speed is 10 m / s. Calculate the energy generated by one wind turbine in 1 hour (3600 seconds). energy = … J [3] (b) The wind turbine uses a generator to produce electricity. Fig. 6.3 shows a simple a.c. generator. S N voltage output Fig. 6.3 (i) Describe how a simple a.c. generator produces a voltage output. … … … … … … [3] (ii) On Fig. 6.4, sketch a graph of voltage output against time for a simple a.c. generator rotating with a constant speed. voltage output time Fig. 6.4 [2] (c) Turbines and generators can also be used to convert the kinetic energy of tidal water into electrical energy. (i) The efficiency of a tidal generator is 80% when the tidal water moves at 5.0 m / s. Calculate the mass of water which would need to pass through the tidal generator to produce 1400 J of electrical energy from kinetic energy. mass = … kg [3] (ii) State one advantage of using tidal generators to produce electricity instead of traditional fossil fuel power stations. … … [1] [Total: 12]

12 marks

Mark scheme: 6(a) (P =) 50 (kW) ; (E =) Pxt / 50 000  3600 ; (E =) 1.8  108 (J) ; 6(b)(i) coil turns / rotates ; magnetic field through the coil changes / coil, moves across / cuts, magnetic field ; (e.m.f. / voltage output is) induced / ref to induction ; 3 6(b)(ii) sinusoidal wave ; with constant amplitude and constant time period ; 2 6(c)(i) (KE = ) 1400 / 0.8 / 1750 (J) ; (m =) 2KE / v2 / 2  1750/25 ; (m =) 140 (kg) ; OR: ½ m.52  0.8 = 1400 ; m = 1400 25 0.8   2 ; = 140 (kg) ; 3 6(c)(ii) doesn’t release, CO2 / greenhouse gases, / doesn’t contribute to, global warming / climate change, / won’t run out / renewable ; 1

This question in 0654/43 May/June 2023

9 A student is investigating electromagnetic induction by dropping a magnet through a coil of wire. The coil of wire is connected to a device which measures the electromotive force (e.m.f.) induced in the coil. Fig. 9.1 shows the equipment used by the student. N direction of motion of magnet S to device to measure e.m.f. coil of wire Fig. 9.1 (a) Fig. 9.2 shows the induced electromotive force (e.m.f.) measured as the magnet falls through the coil of wire. Fig. 9.2 shows two peaks, X and Y. +0.6 peak X +0.4 +0.2 induced e.m.f . / V 0.0 time / s 0.02 0.04 0.06 0.08 –0.2 –0.4 –0.6 peak Y Fig. 9.2 (i) Explain why: peak X is positive and peak Y is negative … … peak Y has a larger magnitude than peak X. … … [2] (ii) The data in Fig. 9.2 was obtained using a coil made of 800 turns of wire. On Fig. 9.2, sketch the data which would be obtained if a coil containing 400 turns was used with the same magnet. [2] (b) When writing up the results, the student is not sure whether to write about the induced potential difference or the induced electromotive force (e.m.f.). Place ticks in Table 9.1 against each statement that is correct for potential difference and for electromotive force (e.m.f.). You may place one or two ticks in each row. The first row has been done for you. Table 9.1 electromotive potential force (e.m.f.) difference is measured in volts 3 3 is equal to work done per unit charge relates to the energy supplied by the source relates to the energy transferred by a circuit component [2] (c) The coil of wire used in the investigation is made of copper. Copper is a solid. Complete the sentences to describe the arrangement of atoms in a solid and the properties of a solid. In a solid, the arrangement of atoms is … . The forces between atoms are … which allows the atoms to … but keeps them in a … position. [2] (d) Copper is a good thermal conductor. Describe how thermal energy is transferred in copper. … … … … [3] [Total: 11]

11 marks

Mark scheme: 9(a)(i) (peak X is positive and peak Y is negative) 2 S causes peak (X) and N causes peak (Y) (as it passes through coil) ; (peak Y has a larger magnitude than X) (idea that) the magnet is increasing in velocity / speed ; 9(a)(ii) 2 same shape graph drawn with line crossing x-axis at same point ; both peaks lower than original ; 9(b) 2 electromotive potential force (e.m.f.) difference is measured in volts ✓ ✓ is equal to work done per unit charge ✓ ✓ relates to the energy supplied by the source ✓ relates to the energy transferred by a circuit component ✓ ;; 9(c) regular / ordered / a lattice 2 strong vibrate fixed ;; four correct = 2 marks two or three correct = 1 mark 9(d) atoms vibrate ; 3 (idea that) vibrations passed on to next atom ; (idea of) transfer by (free) electrons ;

This question in 0654/41 Oct/Nov 2023

9 Fig. 9.1 shows a simple d.c. motor with a coil of wire containing 100 turns. 1.2 N axis of coil N S 35 cm – + Fig. 9.1 (a) The current in the coil causes forces to act on the coil, which make it turn about its axis. (i) Fig. 9.1 shows a force of 1.2 N acting at 90° to the coil, at a distance of 3.5 cm from the axis. Calculate the moment of the force on the coil. moment = … Nm [3] (ii) Suggest how the magnitude of the force in (a)(i) changes when both the number of turns on the coil is doubled and the current is doubled. … … [2] (b) Fig. 9.2 shows a toy boat. The toy boat uses a motor similar to that shown in Fig. 9.1 to propel the toy boat across a pond. Fig. 9.2 The toy boat has a mass of 0.60 kg and travels at a maximum speed of 3.0 m / s. Calculate the maximum kinetic energy of the toy boat. State the unit for your answer. kinetic energy = … unit … [3] (c) Fig. 9.3 shows a speed-time graph for part of the toy boat’s journey. 3.0 2.5 2.0 toy boat’s journey speed m / s 1.5 1.0 0.5 0.0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 time / minutes Fig. 9.3 (i) Use Fig. 9.3 to describe the motion of the toy boat for this part of the journey. … … … [2] (ii) Suggest why the shape of this graph is not a realistic description of the motion of the toy boat at 1.5 minutes. … … … [1] [Total: 11]

11 marks

Mark scheme: 9(a)(i) (3.5 cm =) 0.035 (m) ; 3 (moment =) f  d / 1.2  0.035 ; (moment =) 0.042 (N m) ; or (35 cm =) 0.35 (m) ; (moment =) f  d / 1.2  0.35 ; (moment =) 0.42 (N m); 9(a)(ii) increases ; 2 by a factor of 4; 9(b) (kinetic energy =) ½ mv2 or ½  0.60  3.02 ; 3 (kinetic energy = ) 2.7 ; J / joules ; 9(c)(i) initially / in first 1.5 mins, constant acceleration ; 2 then / after 1.5 min, acceleration is zero / constant speed ; 9(c)(ii) (idea that) change in acceleration would take some time / change more gradually / graph would be a curve at 1.5 mins ; 1

This question in 0654/42 Oct/Nov 2023

6 Fig. 6.1 shows an electric refrigerator. temperature control cooling unit Fig. 6.1 (a) The cooling unit inside the refrigerator is placed at the top of the refrigerator. (i) State the name of the process which transfers most thermal energy from the food to the cooling unit inside the refrigerator. … [1] (ii) Explain, in terms of density changes, why the cooling unit being fitted at the top of the refrigerator allows all of the air inside to be cooled. … … … … … [3] (b) The refrigerator uses the compression and expansion of gases in order to transfer thermal energy to the outside of the refrigerator. Complete Table 6.1 to show how the pressure of a fixed mass of gas changes with temperature and with volume. Table 6.1 temperature volume pressure increases kept constant remains constant increases [1] (c) The cooling unit in the refrigerator uses a motor. Fig. 6.2 shows a simple d.c. motor. coil rotation N S _ + Fig. 6.2 Describe two ways to make a motor turn more slowly. 1 … … 2 … … [2] [Total: 7]

7 marks

Mark scheme: 6(a)(i) convection ; 1 6(a)(ii) air (at the top) is cooled and its density increases ; 3 the cooled air falls ; warm(er) air has lower density and moves upwards ; 6(b) 1 temperature volume pressure increases kept constant increases remains constant increases decreases both correct ; 6(c) any two from: 2 decrease the current in the coil ; use fewer turns on the coil ; use a weaker magnet / magnetic field ;

This question in 0654/43 Oct/Nov 2023

12 A student investigates light dependent resistors (LDRs). Fig. 12.1 shows the circuit the student uses. variable power supply A LDR Fig. 12.1 (a) The ammeter in Fig. 12.1 reads 0.24 A. (i) Calculate the amount of charge flowing through the LDR each minute. State the unit for your answer. charge = … unit … [3] (ii) The student shines a bright desk lamp on the LDR. State and explain the effect this has on the ammeter reading. effect … explanation … … … [2] (iii) The desk lamp emits light with wavelengths ranging from 3.8 × 10–7m to 7.5 × 10–7m. Calculate the minimum frequency of light emitted by the desk lamp. minimum frequency = … Hz [3] (b) The student calculates the resistance of the LDR using the current reading from the ammeter. State what other measurement is required for this calculation. … [1] (c) The variable power supply used by the student uses a transformer to reduce the output. The current in the primary coil of the transformer is 10.5 A and the current in the secondary coil is 4.2 A. The primary coil contains 360 turns and the transformer can be assumed to be 100% efficient. Calculate the number of turns in the secondary coil. number of turns = … [4] [Total: 13]

13 marks

Mark scheme: 12(a)(i) (Q =) It / 0.24  60 ; (in any form) 3 (Q =) 14(.4) ; coulombs / C ; 12(a)(ii) (effect) reading increases ; 2 (explanation) the resistance (of the LDR) decreases ; 12(a)(iii) (f =) speed / wavelength or 3  108 / 7.5  10–7 ; (in any form) 3 use of 3  108 (m / s) ; (f =) 4.0  1014 (Hz) ; 12(b) potential difference / p.d. (across the LDR) ; 1 12(c) use of IpVp = IsVs ; 4 Vp = 4.2 / 10.5 Vs / 0.4 Vs ; (Ns = ) NpVs / Vp / 360/0.4 / 360  2.5 ; (in any form) (Ns = ) 900 ; or use of IpNp = IsNs ; Ns = IpNp / Is ; (10.5  360) / 4.2 ; = 900 ;

This question in 0654/43 Oct/Nov 2023

12 Fig. 12.1 shows a large electromagnet used to lift scrap metal. electromagnet crane car Fig. 12.1 (a) The electromagnet lifts the car to a height of 15 m. The car has a mass of 1200 kg. Calculate the work done on the car when it is lifted to a height of 15 m. The gravitational field strength is g = 10 N / kg. work done = … J [2] (b) The electromagnet is made from a solenoid. Fig. 12.2 shows a solenoid. current current current Fig. 12.2 (i) On Fig. 12.2 draw the pattern of the magnetic field produced when a current passes through the solenoid. Include an arrow showing the direction of the magnetic field. [2] (ii) The solenoid uses a current of 50 A. Calculate the amount of charge which flows through the solenoid in 30 s. State the unit for your answer. charge = … unit … [3] (iii) The solenoid has a resistance of 5.0 Ω when the current is 50 A. Calculate the power of the electromagnet. power = … W [4] (c) Electromagnets can be made much stronger than permanent magnets. State one other advantage of using an electromagnet to lift scrap metal. … … [1] [Total: 12]

12 marks

Mark scheme: 12(a) (W =) mgh / 1200  10  15 ; 2 (W =) 180 000 (J) ; 12(b)(i) correct shape of field ; 2 correct direction indicated on at least one field line ; 12(b)(ii) (Q =) It / 50  30 ; 3 (Q =) 1500 ; C / coulombs ; 12(b)(iii) (V =) IR / 50  5.0 ; 4 (V =) 250 (V) ; (P =) IV / 50  250 ; (P =) 12 500 (W) ; 12(c) can be switch off / on; 1

This question in 0654/42 Feb/March 2024

6 Fig. 6.1 shows an electric pressure‑washer being used to wash a car. to power supply Fig. 6.1 (a) The pressure‑washer pumps water at a high pressure through a small nozzle. The cross‑sectional area of the nozzle is 5.0 × 10–6 m2. The water leaves the nozzle with a pressure of 9.0 × 106 Pa. Calculate the force exerted by the water as it leaves the nozzle. force = … N [2] (b) The pressure‑washer uses a d.c. motor to pump the water out of the nozzle. Fig. 6.2 shows a diagram of a simple d.c. motor. N X S _ + Fig. 6.2 (i) The arrows on Fig. 6.2 show the direction of the current. Draw an arrow to show the direction of the force acting on the coil at the point labelled X. [1] (ii) Describe the function of the split‑ring commutator in a simple d.c. motor. … … … … [2] (c) After the car has been washed, droplets of cold water remain on the roof of the car. After a few minutes, the droplets of water have disappeared. (i) State the name of the process which causes the droplets of water to disappear. … [1] (ii) Describe the process which causes the droplets of water to disappear in terms of molecules. … … … [2] [Total: 8]

8 marks

Mark scheme: 6(a) (F=) 45 (N) ; 2 6(b)(i) arrow drawn upwards ; 1 6(b)(ii) provides an alternating current (in the coil) / current that changes direction every half-turn / to reverse the current every half turn / 180° ; allows coil to continue to turn (in the same direction) ; 2 Question Answer Marks 6(c)(i) evaporation ; 1 6(c)(ii) the most energetic molecules ; escape from the surface ; 2

This question in 0654/42 May/June 2024

6 Fig. 6.1 shows a mobile phone (cell phone) on a wireless charging pad. mobile phone screen wireless charging pad mains cable Fig. 6.1 (a) The screen of the mobile phone is made from glass. When light travels from air into glass it is refracted and changes direction. (i) Place one tick (3) in each row of Table 6.1 to state the effect on the properties of frequency, speed and wavelength for light as the light travels from air into glass. Table 6.1 decreases stays the same increases frequency speed wavelength [3] (ii) A ray of light is incident on the screen of the mobile phone. The angle of incidence is 53°. The refractive index of glass is 1.5. Calculate the angle of refraction r. r = … ° [2] (b) The mobile phone battery holds a maximum charge of 3300 C. The current used to charge the battery is 0.60 A. Calculate the time taken to fully charge the mobile phone battery. time taken = … s [2] (c) The wireless charging pad in Fig. 6.1 contains a coil of wire. The mains cable provides an alternating current (a.c.) to the coil of wire. The mobile phone contains a second coil of wire. Describe how an electromotive force (e.m.f.) is induced in the second coil of wire when the mobile phone is placed on the charging pad. … … … … [2] [Total: 9]

9 marks

Mark scheme: 6(a)(i) (frequency) stays the same ; 3 (speed) decreases ; (wavelength) decreases ; 6(a)(ii) sin i sin i sin 53 2 evidence of n = or 1.5 = or 1.5 = ; sin r sin r sin r 32(°) ; 6(b) evidence of Q = It or 3300 ÷ 0.60 ; 2 5500 (s) ; 6(c) (idea that) there is a (changing) magnetic field around the coil of wire (in the charging pad) ; 2 the second coil experiences a changing magnetic field (which induces the e.m.f.) ;

This question in 0654/41 Oct/Nov 2024

3 Fig. 3.1 shows a wind turbine used to generate electricity. Fig. 3.1 (a) State one advantage of generating electricity using wind turbines. … … [1] (b) The wind turbine contains an alternating current (a.c.) generator. On Fig. 3.2, sketch a graph of output voltage against time for the a.c. generator when the wind turbine is turning at a constant speed. output voltage time Fig. 3.2 [2] (c) A step-up transformer is used to increase the voltage from the generator. Describe the construction of a basic step-up transformer. You may include a labelled diagram to aid your description. … … … … … [3] (d) The wind exerts a pressure of 7200 Pa on each blade of the wind turbine. Each blade has a surface area of 90 m2. Calculate the force exerted by the wind on each turbine blade. force = … N [2] (e) The wind turbines produce a low-pitch sound when they turn. (i) State the minimum frequency of sound which can be heard by a healthy human ear. frequency = … Hz [1] (ii) Sound waves are longitudinal waves. Describe, in terms of oscillations and energy transfer, what is meant by a longitudinal wave. … … … [1] [Total: 10]

10 marks

Mark scheme: 3(a) does not release CO2 / does not release greenhouse gases / does not contribute to global warming / climate change / no 1 fuel costs / renewable / AVP ; 3(b) sinusoidal waveform ; 2 constant time period and amplitude ; 3(c) (soft) iron core ; 3 two coils wrapped around the same core ; number of turns on primary less than secondary / number of turns on secondary more than primary ; 3(d) evidence of F = P  A or 7200  90 ; 2 650 000 (N) ; 3(e)(i) 20 (Hz) ; 1 3(e)(ii) (direction of) oscillations are parallel to direction of energy transfer ; 1

This question in 0654/42 Oct/Nov 2024

10 (a) Fig. 10.1 shows a simple d.c. motor. axis of rotation magnet magnet coil N B C S A D split-ring commutator brush brush current current battery Fig. 10.1 (i) Explain why the side AB of the coil experiences a force when a current is in the coil. … … … [2] (ii) Describe how forces on sides AB and CD cause a turning effect on the coil when a current is in the coil. … … … [2] (iii) Describe how the split-ring commutator and brushes ensure the coil rotates continuously in the same direction. … … … [2] (b) (i) Circle the component which is part of a basic transformer. cell permanent magnet soft‑iron core straight wire [1] (ii) An ideal transformer has 2500 turns on the primary coil and 400 turns on the secondary coil. There is a voltage of 230 V across the primary coil. Calculate the voltage across the secondary coil. voltage = … V [2] (iii) The current in the secondary coil is 1.6 A. Calculate the current in the primary coil. current = … A [2] (iv) State the assumption made in the calculation in (b)(iii). … [1] [Total: 12]

12 marks

Mark scheme: 10(a)(i) current-carrying wire / coil, is in a magnetic field ; 2 that interacts with the magnetic field of magnets ; 10(a)(ii) forces act in opposite directions ; 2 idea of forces not along the same line / or creating a moment ; 10(a)(iii) reverses the direction of the current in the coil ; 2 every half turn ; 10(b)(i) soft-iron core ; 1 10(b)(ii) evidence of Vp / Vs = Np / Ns or 230 / Vs = 2500 / 400 ; 2 37 (V) ; 10(b)(iii) evidence of IpVp = IsVs or Ip  230 = 1.6  37 ; 2 0.26 (A) ; 10(b)(iv) 100% efficient ; 1

This question in 0654/42 Feb/March 2025

10 (a) A student investigates a simple d.c. motor. Fig. 10.1 shows a diagram of a simple d.c. motor. magnet N coil S _ + axis of rotation component X Fig. 10.1 (i) The motor consists of a current-carrying coil in a magnetic field. The coil experiences a turning effect. State three ways the turning effect can be increased. 1 … 2 … 3 … [3] (ii) State the name of component X. … [1] (iii) Describe how component X is used to give continuous rotation of the coil. … … … [2] (b) Transformers are used in the distribution of electricity. (i) State the type of transformer used at power stations to supply power to the electricity network. … [1] (ii) Explain why the use of this transformer means power losses in transmission cables are smaller. … … … [3] (c) A transformer is connected to a 230 V mains supply. An output of 3.6 V is required. The secondary coil has 720 turns. Calculate the number of turns on the primary coil. number of turns = … [2] [Total: 12]

12 marks

Mark scheme: 10(a)(i) more turns of wire / more turns on the coil ; 3 increase current ; stronger magnetic field ; 10(a)(ii) split-ring commutator ; 1 10(a)(iii) reverses the direction of the current (in the coil) ; 2 every half a turn ; 10(b)(i) step-up ; 1 10(b)(ii) higher voltage ; 3 means lower current (for same power transferred) ; (reference to) P = I²R or (reference to) P  I² or power loss proportional to current squared or energy loss proportional to current squared ; 10(c) evidence of Vp / Vs = Np / Ns or 230 / 3.6 = Np / 720 ; 2 46 000 ;

This question in 0654/41 Oct/Nov 2025

12 (a) (i) Describe the construction of a step-up transformer. You may wish to draw a labelled diagram. … … … [2] (ii) A step-up transformer reduces the current in an electricity transmission wire from 20 000 A to 500 A. Calculate the power lost in a wire with resistance 0.60 Ω when the current is 500 A. power lost = … W [2] (b) An electrical current can be either direct or alternating. State the difference between direct current (d.c.) and alternating current (a.c.). … … … [1] (c) Fig. 12.1 shows a simple a.c. generator used to produce electricity. rotating coil N magnet S slip rings brushes a.c. output Fig. 12.1 (i) Explain why slip rings are required. … … … [2] (ii) The coil in the generator is rotated at a constant speed. On Fig. 12.2 sketch a graph of e.m.f. against time for the output of the a.c. generator. e.m.f. 0 0 time Fig. 12.2 [2] (iii) The speed of rotation of the coil in the generator is doubled. Describe how the e.m.f. against time graph changes. … … … [2] [Total: 11]

11 marks

Mark scheme: 12(a)(i) primary coil with fewer turns (than secondary) / ORA ; 2 soft iron core ; 12(a)(ii) P = I²R or 500²  0.6 ; 2 150 000 (W) ; 12(b) (d.c.) electric charge (only) flows in one direction / current (only) flows in one direction 1 OR (a.c.) electric charge changes / reverses direction (periodically) / current changes / reverses direction (periodically) ; 12(c)(i) maintain a connection to each side of the coil ; 2 so wires do not twist / so wires do not tangle ; 12(c)(ii) sine wave with positive and negative e.m.f. ; 2 constant amplitude and period ; 12(c)(iii) amplitude doubles ; 2 period halves or frequency doubles ;

This question in 0654/43 Oct/Nov 2025