Cambridge IGCSE Physics 0625 — 2014 Oct/Nov Paper 5 · Variant 3

1 In this experiment, you will investigate the magnification produced by a converging lens. Carry out the following instructions, referring to Fig. 1.1. illuminated u object screen lens h0 Fig. 1.1 (a) Measure and record the height h0 of the triangular object. h0 = ......................................................... cm (b) (i) Switch on the lamp. (ii) Set the distance u between the illuminated object and the lens to 30.0 cm. (iii) Move the screen until a sharp image of the illuminated object is seen. (iv) Measure, and record in Table 1.1, the height hI of the image. Table 1.1 u / cm hI / cm S 30.0 35.0 40.0 45.0 50.0 55.0 [3] (v) Repeat (b)(iii) and (b)(iv) for u values of 35.0 cm, 40.0 cm, 45.0 cm, 50.0 cm and 55.0 cm. (vi) Switch off the lamp. (c) For each distance u calculate, and record in the table, a value S using your results from (a) h0 and (b) and the equation S = . hI (d) Plot a graph of S (y-axis) against u / cm (x-axis). [5] (e) (i) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = .......................................................... [1] 1 (ii) Calculate the focal length f of the lens, where f = cm. G f = .......................................................... [1] [Total: 10]

Mark scheme: 1 (a) h0 in range 1.5 to 2.5 (cm) and to at least 1dp [1] (b)(c) hI values decreasing [1] correct S calculations and S values all > 0.8 [1] (d) graph: axes labelled with quantity and unit and in correct orientation [1] appropriate scales [1] plots correct to ½ small square [1] well-judged straight line and thin continuous line, precise plots [1] triangle method/information for gradient seen marked on graph [1] (e) (i) G calculated from at least ½ line [1] (ii) f in range 14 – 16 (cm) [1] [Total: 10]

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2 In this experiment, you will investigate how the surface of a container affects the rate at which water cools. Two test-tubes, labelled A and B, have been set up for you. Test-tube A has no covering. Test-tube B is covered with foil. Each test-tube has a mark to show the required water level. Carry out the following instructions, referring to Fig. 2.1. °C °C cork water level mark A B foil Fig. 2.1 (a) (i) Remove the cork and thermometer from test-tube A. Pour hot water into the test-tube, up to the mark. (ii) Carefully replace the cork and thermometer. Wait for about 30 seconds before taking any measurements. (iii) Start the stopclock and read the thermometer. In the first row of Table 2.1, record this temperature θ at time t = 0 s. (iv) Record, in the table, the temperature θ of the thermometer at times t = 30 s, 60 s, 90 s,120 s,150 s and 180 s. (v) Complete the column headings and column t values in the table. Table 2.1 test-tube A test-tube B t / θ/ θ/ [5] (b) (i) Remove the cork and thermometer from test-tube B. Pour hot water into the test-tube, up to the mark. (ii) Repeat steps (a)(ii) to (a)(iv). (c) State in which test-tube, A or B, the water cools at the greater rate. Justify your answer by referring to your results. test-tube .......................... justification ................................................................................................................................ ................................................................................................................................................... ................................................................................................................................................... [2] (d) Suggest one aspect of the practical procedure which may be a source of unreliability in the experiment. ................................................................................................................................................... .............................................................................................................................................. [1] (e) Another IGCSE student wants to extend your experiment in order to test the effects of other surface materials. Suggest two factors relating to the apparatus which she should keep the same in order for the tests to be a fair comparison. 1. .............................................................................................................................................. ................................................................................................................................................... 2. .............................................................................................................................................. ................................................................................................................................................... [2] [Total: 10]

Mark scheme: 2 (a)(b) table: units all correct, s ° C ° C NOT C°, NOT centigrade [1] t values correct 0, 30, 60, 90, 120, 150, 180 [1] θ for A and B decreasing [1] final interval less than initial in both sets [1] both sets of data to precision of at least 1 ° C [1] (c) statement matching temperature changes with justification referring to results and involving correct comparative change in temperature [1] justification has specific mention of temperature change in the same time owtte [1] (d) appropriate source of inaccuracy associated with procedure e.g. any one from: • water levels not the same • thermometer scales not read at 90° • initial temperatures different • not able to stir water • not waiting for temperature to stabilise initially / waiting time not long enough [1] (e) any two factors relating to apparatus from: • keep thermometer at same depth • same size / thickness / material of test-tube / same test tube • same water levels / volume / quantity / amount of water • same thickness / surface area of surface material [2] [Total: 10]

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3 In this experiment, you will determine the resistance of a lamp in different electrical circuits. Circuit 1 has been set up for you as shown in Fig. 3.1. Do not alter the connections of the lamp, voltmeter and ammeter between terminals X and Y during the whole experiment. Carry out the following instructions, referring to Fig. 3.1. circuit 1 power supply L A X Y V Fig. 3.1 (a) (i) Switch on. Measure, and record in Table 3.1, the potential difference V and the current I for lamp L. Switch off. Table 3.1 circuit V / I / R / 1 2 3 [6] V (ii) Calculate, and record in the table, the resistance R of lamp L, using the equation R = . I (iii) Complete the column headings in the table. (b) (i) Disconnect terminal Y from the circuit. Use the extra lamps and leads which have been provided to connect circuit 2 as shown in Fig. 3.2. circuit 2 power supply L A X Y V Fig. 3.2 (ii) Repeat steps (a)(i) and (a)(ii). (c) (i) Disconnect terminal Y from the circuit. Use the lamps and leads which have been provided to connect circuit 3 as shown in Fig. 3.3. circuit 3 power supply L A X Y V Fig. 3.3 (ii) Repeat steps (a)(i) and (a)(ii). (d) A student suggests that, as the same lamp L is used throughout the experiment, its resistance in each circuit should be the same. State whether your findings agree with this idea. Justify your answer by reference to your results. statement .................................................................................................................................. ................................................................................................................................................... justification ................................................................................................................................ ................................................................................................................................................... ................................................................................................................................................... [1] (e) Theory suggests that the resistance of a lamp increases if its temperature rises. Explain whether or not your observations support this. ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [1] (f) It is possible to obtain sets of readings in this experiment by using a variable resistor rather than rearranging the circuit. In the space below, redraw circuit 1 showing how a variable resistor could be included for this purpose. [2] [Total: 10]

Mark scheme: 3 (a)(b)(c) table: p.d.s all < 3.0 V and to at least 1 d.p. [1] currents all < 1.00 A and to at least 2 d.p. [1] units all correct (V, A, Ω) [1] R calculations correct [1] V, I and R values all decreasing [1] 2 or 3 sig. figs. in R column [1] (d) statement matches results, with matching justification which refers to values being ‘too different’ / ‘difference beyond limits of experimental accuracy’ owtte [1] (e) lamp in circuit 1 brighter than in circuits 2 and 3 and has greater resistance [1] (f) correct circuit symbol for variable resistor (rectangle with strike-through arrow only) [1] connected in correct series circuit [1] [Total: 10]

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4 In this experiment, you will investigate the downward deflection of a metre rule clamped at one end. The metre rule has been set up for you and you are provided with an object M. Carry out the following instructions, referring to Fig. 4.1. clamp metre rule free end h0 floor Fig. 4.1 (a) Measure and record the height h0 of the free end of the metre rule above the floor as indicated in Fig. 4.1. h0 = ................................................... cm [1] (b) Carefully place M on the rule at a distance d = 60.0 cm from the free end of the rule, as shown in Fig. 4.2. M h Fig. 4.2 (i) Explain how you made sure that M was at the 60.0 cm mark. You may use a diagram. ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [1] (ii) Measure, and record in Table 4.1, the new height h of the free end above the floor, as indicated in Fig. 4.2. Table 4.1 d / cm h / cm H / cm (d × H) / cm2 60.0 50.0 40.0 30.0 20.0 [4] (iii) Repeat (b)(ii) for d = 50.0 cm, d = 40.0 cm, d = 30.0 cm and d = 20.0 cm. (c) (i) For each value of d, calculate and record in the table the downward deflection H (change in height) produced by M. Use your results from (a) and from the table and the equation H = h0 − h. (ii) For each value of d, calculate and record in the table the value of (d × H). Use your results from the table. (d) A student suggests that d is inversely proportional to H (that is, d is proportional to 1 / H). Using some appropriate figures from Table 4.1, explain why this cannot be the case. ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [1] (e) (i) When the metre rule is clamped in this way, the free end is slightly deflected downwards even before M is placed on it. Explain why this deflection occurs. ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [1] (ii) Suggest how you could find the value of this deflection. You may draw a diagram. ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [2] [Total: 10]

Mark scheme: 4 (a) h0 less than 100 cm [1] (b) (i) suitable explanation, e.g. same no. of graduations between 60 cm mark and each end of object owtte, or mark on side of rule and object [1] (ii)(iii) table: h values all decreasing [1] h values to at least 1 d.p. [1] (c) (i) correct calculations of H [1] (ii) correct d × H calculations [1] (d) d × H not constant / H doesn’t always double when d halves owtte [1] (e) (i) reference to mass/weight of rule [1] (ii) measure height at bench [1] subtract h0 [1] [Total: 10]

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