Cambridge IGCSE Physics 0625 — 2020 Oct/Nov Paper 5 · Variant 2

1 In this experiment, you will investigate the stretching of a spring. Carry out the following instructions, referring to Fig. 1.1. metre rule spring clamp stand bench Fig. 1.1 (a) The metre rule is clamped in position near to the spring. Do not change the position of the metre rule. (i) Use the set square provided to take readings from the metre rule to determine the unstretched length L of the coiled part of the spring. Record the value of L. L = ...................................................mm [1] (ii) Draw a diagram to show clearly how you used the set square to obtain an accurate reading from the metre rule. [1] (b) • Suspend a load P = 0.20 N on the spring. Record in Table 1.1 the new length l of the spring. • Repeat the procedure using loads P = 0.40 N, 0.60 N, 0.80 N and 1.00 N. Table 1.1 P / N l / mm 0.20 0.40 0.60 0.80 1.00 [2] (c) Plot a graph of l / mm (y-axis) against P / N (x-axis). Start both axes at the origin (0,0). (d) The intercept on the y-axis of the graph is numerically equal to the length l0 of the spring when P = 0. Determine the value of l0. Show clearly on the graph how you obtained the necessary information. l0 = ......................................................... [2] (e) Calculate L – l0. L – l0 = ......................................................... [1] [Total: 11]

Mark scheme: 1(a)(i) L value in mm 1 1(a)(ii) clear diagram showing horizontal line of set square across to metre rule 1 1(b) l values increasing 1 all > L 1 1(c) graph: axes correctly labelled and right way round 1 suitable scales 1 all plots correct to ½ small square 1 good line judgement, thin, continuous line 1 1(d) intercept method clearly shown 1 l0 value correctly read to ½ small square 1 1(e) L – l0 = 0 ± 2 mm 1

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2 In this experiment, you will investigate the refraction of light in a transparent block. Carry out the following instructions, using the separate ray-trace sheet provided. Refer to Fig. 2.1. E hole N 30° F A B D C G ray-trace sheet L eye Fig. 2.1 (a) • Place the transparent block, largest face down, on the ray-trace sheet supplied. The block should be approximately in the middle of the paper. • Draw and label the outline of the block ABCD. • Remove the block and draw the normal NL at the centre of side AB. Continue the normal so that it passes through side CD of the block. • Label the point F where the normal NL crosses side AB. • Label the point G where the normal NL crosses side CD. [1] (b) (i) • Draw the line EF at an angle i = 30° to the normal as shown in Fig. 2.1. • Place the paper on the pin board. • Place two pins P1 and P2 on line EF at a suitable distance apart for this experiment. • Replace the block and look from the position of the eye shown in Fig. 2.1, to observe the images of P1 and P2 through side CD of the block. Adjust your line of sight until the images of P1 and P2 appear one behind the other. • Place two pins P3 and P4 between your eye and the block so that P3, P4, and the images of P1 and P2 seen through the block, appear one behind the other. • Label the positions of P1, P2, P3 and P4. • Remove the block and the pins. • Draw a line joining the positions of P3 and P4. Continue the line through the outline of the block until it extends to just outside the outline of the block. Label the end of the line K. • Label the point H where the line meets side CD. • Label the point J where the line meets the normal NL. • Draw the line FH. [2] (ii) Measure and record the length a of the line GH. a = ......................................................... [1] (iii) Measure and record the length b of the line FH. b = ......................................................... [1] (c) Measure and record the acute angle θ between the line NL and the line JK. An acute angle is less than 90°. θ = ......................................................... [2] (d) State one precaution that you took in order to produce an accurate ray-trace. ................................................................................................................................................... ............................................................................................................................................. [1] (e) A student suggests that i should be equal to θ within the limits of experimental accuracy. In this experiment, i = 30 °. Suggest a range of values for θ that match this suggestion for your experiment. range .................................................................................................................................. [1] (f) A student plans to test the suggestion that, in this experiment, i = θ for all possible values of i. Explain briefly how you would test the suggestion. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] Tie your ray-trace sheet into this Question Booklet between pages 6 and 7. [Total: 11]

Mark scheme: 2(a) normal in centre of AB to 2 mm and at 90° F and G correctly labelled 1 2(b)(i) P1P2 pin separation at least 5.0 cm 1 all lines in approximately correct positions and neat 1 2(b)(ii) a correct to ± 1 mm 1 2(b)(iii) b correct to ± 1 mm 1 2(c) candidate’s θ correct to ± 2(°) 1 θ = 30 ± 2° unit needed 1 2(d) any one from: thin lines / thin pins / sharp pencil view bases of pins ensure pins vertical / perpendicular to ray trace sheet use large pin separation (securely) attach the ray trace sheet to the surface 1 2(e) maximum range 27(°) – 33(°) 1 2(f) repeat experiment using more i values 1 uses at least 4 i values 1

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3 In this experiment, you will investigate the resistance of samples of resistance wire. Carry out the following instructions, referring to Fig. 3.1. The circuit shown in Fig. 3.1 has been provided for you. power supply A resistance wire C D B E Fig. 3.1 Table 3.1 shows how the samples of wire are connected into the circuit. Table 3.1 section resistance wire BC one 30 cm piece CD two 30 cm pieces DE three 30 cm pieces (a) (i) • Switch on. • Measure the current I in the circuit. I = ......................................................... [1] (ii) Connect the voltmeter across section BC of the resistance wire. Measure and record the potential difference (p.d.) V1 across section BC. Switch off. V1 = ......................................................... [1] V1 Calculate the resistance R1 of section BC using the equation R1 = . I Give your answer to a suitable number of significant figures for this experiment and include the unit. R1 = ......................................................... [1] (iii) Disconnect the voltmeter and its leads from section BC. Connect the voltmeter across section CD. Switch on. Measure and record the potential difference (p.d.) V2 across section CD. Switch off. V2 = ............................................................... V2 Calculate the resistance R2 of section CD using the equation R2 = . Give your answer I to a suitable number of significant figures for this experiment and include the unit. R2 = ......................................................... [1] (iv) Disconnect the voltmeter and its leads from section CD. Connect the voltmeter across section DE. Switch on. Measure and record the potential difference (p.d.) V3 across section DE. Switch off. V3 = ............................................................... V3 Calculate the resistance R3 of section DE using the equation R3 = . Give your answer I to a suitable number of significant figures for this experiment and include the unit. R3 = ............................................................... [3] (b) (i) The sections BC, CD and DE are all the same length and made of the same metal. Tick the box to show your conclusion from the results. The resistance of a section increases as the number of wires increases The resistance of a section decreases as the number of wires increases The resistance of a section is independent of the number of wires. [1] (ii) Justify your conclusion in (b)(i) by reference to your results. ........................................................................................................................................... ..................................................................................................................................... [1] (c) Explain how you would change this experiment to investigate the relationship between the length of a sample of wire and its resistance. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] [Total: 11]

Mark scheme: 3(a)(i) 1 3(a)(ii) V1 to at least 1 decimal place and < 3 V 1 R1 correct 1 3(a)(iii) V2 present, R2 correct and units V and A 1 3(a)(iv) V3 present, R3 present and to 2 or 3 significant figures 1 Unit Ω 1 R1 = 3 × R3 to within 10% 1 3(b)(i) expect second box ticked 1 3(b)(ii) correct justification using results 1 3(c) use different lengths (of the wire sample) 1 measure the p.d. and current / determine the resistance (of each length) 1

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4 A student investigates the length of time taken for ice cubes to melt when they are placed in water. She uses beakers of water at different temperatures to investigate how the initial temperature of the water affects the time taken for the ice cubes to melt. Plan an experiment to investigate how the initial temperature of the water affects the time taken for the ice cubes to melt. You are not required to carry out this experiment. The following apparatus is available: thermometer supply of ice cubes 250 cm3 beakers supply of cold water In your plan, you should: • write a list of additional apparatus to use • explain how to carry out the investigation • state the key variables to keep constant • draw a table, or tables, with column headings, to show how to display the readings (you are not required to enter any readings in the table) • explain how to use the readings to reach a conclusion. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 MP1 Apparatus: method of heating water and timer 1 MP2 Method: measure the temperature of the water and place the ice cube(s) in the water and measure the time taken to melt 1 MP3 repeat with water at different temperature(s) 1 MP4, MP5 Key variables: Any two from: mass / volume of ice cubes number / size of ice cubes (per test) temperature of ice cubes / keep ice cubes in a freezer room temperature volume of water in the beaker amount of stirring 2 MP6 Table: table with columns for time / t and water temperature with correct units 1 MP7 Conclusion: explanation of how to reach a conclusion 1 Additional graph notes: NOTE: The principle to apply here is ‘could I draw a significantly better line, using these points, under examination conditions?’ If the answer is definitely ‘yes’, do not award the mark. NOTE: If candidate’s scale consists of actual readings at equal intervals this will produce a perfect straight line! The only mark available in this case is the first (axes right way round and labelled) So maximum 1. – If axes are wrong way round, the other 3 marks are still available.

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