Cambridge IGCSE Physics 0625 — 2015 May/June Paper 5 · Variant 1

1 In this experiment, you will determine the weight of a metre rule using a balancing method. Carry out the following instructions, referring to Fig. 1.1. 50.0 cm mark P metre rule x y 90.0 cm mark bench pivot Fig. 1.1 (a) Place the metre rule on the pivot. Place the load P on the metre rule at the 90.0 cm mark. Keeping P at the 90.0 cm mark, adjust the position of the metre rule on the pivot so that the metre rule is as near as possible to being balanced. (i) Write down the reading on the metre rule at the position of the pivot. The pivot is at the .................... cm mark of the metre rule. (ii) Record the distance x from the 90.0 cm mark to the pivot. x = ...........................................................[1] (iii) Record the distance y from the pivot to the 50.0 cm mark. y = ...........................................................[1] Px (iv) Determine the weight W of the metre rule using the equation W = , where P = 2.0 N. y P is the weight of load P. W = ...........................................................[1] (b) Keep the pivot at the same position, as recorded in (a)(i). Move load P to the 95.0 cm mark. Place the load Q on the metre rule and adjust its position so that the rule balances. (i) On Fig. 1.2 mark, with a letter X, the approximate position of Q. [1] 50.0 cm mark P a 95.0 cm mark bench pivot Fig. 1.2 (ii) Record the distance a from the 95.0 cm mark to the pivot. a = ............................................................... (iii) Record the distance b from Q to the pivot. b = ............................................................... (iv) Record the distance c from the 50.0 cm mark to the pivot. c = ............................................................... [1] (v) Calculate the product aP, where P = 2.0 N. Include the unit. aP = ............................................................... (vi) Calculate the product bQ, where Q = 1.0 N. Q is the weight of load Q. bQ = ............................................................... (vii) Calculate the product cW, using the value of W determined in part (a)(iv). cW = ............................................................... [2] (c) A student suggests that aP should be equal to bQ + cW. State whether your results support the suggestion. Justify your answer by reference to the results. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... [2] (d) Suggest one practical reason why it is difficult to obtain exact results with this experiment. ................................................................................................................................................... ...............................................................................................................................................[1] [Total: 10]

Mark scheme: 1 (a)(i)(ii) mark recorded between 85 and 60 cm, with matching x value [1] (iii) y value < 40 cm, x and y with correct unit [1] (iv) W correct (N) [1] (b) (i) sensible position for X [1] (ii)–(iv) a = x + 5; b = 10 ± 4; c = y [1] (v)–(vii) cW = (aP – bQ) ±10% [1] correct unit: N cm [1] (c) statement matches results (expect YES, owtte) [1] justified with reference to results; must include the idea of being close enough to be within limits of experimental accuracy [1] (d) difficulty in achieving balance OR difficulty in positioning load in correct position due to markings being covered by the load [1] [Total: 10]

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2 In this experiment, you will investigate the cooling of water. Carry out the following instructions referring to Fig. 2.1. You are provided with a beaker containing hot water and a thermometer. thermometer water Fig. 2.1 (a) (i) Place the thermometer in the beaker of water. When the thermometer reading stops rising, measure the temperature θ of the water and immediately start the stopclock. Record θ in Table 2.1 at time t = 0 s. (ii) In Table 2.1, record the temperature of the water at 30 s intervals until you have a total of six values up to time t = 150 s. Table 2.1 t / s θ / °C 0 30 60 90 120 150 [3] (b) Plot a graph of θ / °C (y-axis) against t / s (x-axis). [5] (c) (i) State whether the rate of cooling of the water in the beaker increases, decreases or stays approximately constant during the period of cooling. The rate of cooling of the water .....................................................................................[1] (ii) Justify your statement by reference to the graph. ........................................................................................................................................... ........................................................................................................................................... .......................................................................................................................................[1] [Total: 10]

Mark scheme: 2 (a) (i) sensible value for θ [1] (ii) Table: temperatures decreasing with final difference not more than first difference [1] evidence of temperatures to 1 ºC or better [1] (b) Graph: • axes correctly labelled, right way round and with units [1] • suitable scales, plots occupying at least half grid in both directions [1] • all plots correct to within ½ small square [1] • good best-fit line judgement [1] • single, thin, continuous line [1] (c) (i) statement to match graph line [1] (ii) statement justified by reference to the graph [1] [Total: 10]

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3 In this experiment, you will investigate the resistance of lamp filaments in series and parallel circuits. The circuit shown in Fig. 3.1 has been set up for you. power supply A V Fig. 3.1 (a) (i) Switch on. Measure and record the potential difference VS across the lamps and the current IS in the circuit. Switch off. VS = ............................................................... IS = ............................................................... [2] VS (ii) Calculate the resistance RS of the lamp filaments using the equation RS = . IS RS = ...........................................................[1] (b) The circuit is to be rearranged so that • the lamps are in parallel • the ammeter will measure the total current in the circuit • the voltmeter will measure the potential difference across the lamps. Draw a diagram of this circuit using standard circuit symbols. [2] (c) Rearrange the circuit as described in (b). (i) Switch on. Measure and record the potential difference VP across the lamps and the current IP in the circuit. Switch off. VP = ............................................................... IP = ............................................................... [1] VP (ii) Calculate the resistance RP of the lamp filaments using the equation RP = . IP RP = ............................................................... RS (iii) Calculate the ratio . RP RS = ............................................................... RP [2] RS(d) A student wishes to investigate whether the ratio for the two lamps is the same under all conditions. RP (i) Suggest a variable that you could change in order to obtain further sets of readings. You are not asked to take any further readings. ........................................................................................................................................... (ii) Explain briefly how you would change this variable. ........................................................................................................................................... ........................................................................................................................................... [2] [Total: 10]

Mark scheme: 3 (a) (i) V to at least 1 dp and < 4 V [1] I to at least 2 dp and < 1 A [1] (ii) RS calculated correctly [1] (b) lamps in parallel [1] voltmeter in correct position, with rest of circuit and symbols correct [1] (c) (i) V and I recorded with correct units with correct PD, current and resistance units [1] (ii) RP to 2 or 3 significant figures [1] (iii) RS / RP ratio calculated correctly and > 1 [1] (d) (i) voltage or p.d., accept current [1] (ii) adjust power supply OR add resistor / variable resistor [1] [Total: 10]

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4 In this experiment, you will investigate the refraction of light passing through a transparent block. Carry out the following instructions, referring to Fig. 4.1. hole N F J G H A E B D M C L ray-trace sheet eye Fig. 4.1 (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 the outline of the block ABCD. (b) Remove the block and draw a normal NL at the centre of side AB. Label the point E where the normal crosses AB. Label the point M where the normal crosses CD. (c) Draw a line GH, parallel to AB and 6.0 cm above AB. Label the point J where the normal crosses GH. (d) Draw a line, starting at E, to the left of the normal and at an angle of incidence i = 30° to the normal as shown in Fig. 4.1. Label the point F where the line meets GH. (e) Place two pins P1 and P2 on the line FE, placing one pin close to E. Label the positions of P1 and P2. (f) Replace the block and observe the images of P1 and P2 through side CD of the block so that 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 and P4, and the images of P1 and P2 seen through the block, appear one behind the other. Label the positions of P3 and P4. Remove the block. (g) Draw a line joining the positions of P3 and P4. Continue the line until it meets CD and label this point K. Draw the line KE. (h) (i) Measure and record the length a between points F and J. a = ............................................................... (ii) Measure and record the length b between points F and E. b = ............................................................... (iii) Measure and record the length c between points E and K. c = ............................................................... (iv) Measure and record the length d between points M and K. d = ............................................................... [2] ac (i) Calculate n, the refractive index of the material of the block, using the equation n = . bd n = .......................................................... [1] (j) Repeat steps (d) – (h) but with the angle of incidence i = 50°. a = ............................................................... b = ............................................................... c = ............................................................... d = ............................................................... n = ............................................................... [2] (k) Suggest one precaution that you should take with this experiment to obtain reliable results. ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[1] Tie your ray-trace sheet into this Booklet between pages 10 and 11. [4]

Mark scheme: 4 Ray-trace: • normal at 90º and in correct position [1] • first angle of incidence = 30º ± 1º and GH in correct position ± 2 mm [1] • all lines present and neat, both sets, in approximately the correct positions [1] • first P1P2 distance ù 5 cm [1] (h) a and b correct to ± 2 mm [1] c and d correct to ± 2 mm and correct unit [1] (i) n correct, no unit, 2 or 3 significant figures [1] (j) complete set of sensible readings [1] both n values 1.4 – 1.6 [1] (k) any one from: • large pin separation • ensure pins are vertical • view bases of pins • drawing thin lines / use a sharp pencil • use thin pins [1] [Total: 10]

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