Cambridge IGCSE Physics 0625 — 2013 May/June Paper 5 · Variant 3

1 In this experiment, you will determine the magnification produced by a converging lens. For Examiner’s Carry out the following instructions, referring to Fig. 1.1. Use The distance u between the illuminated triangle and the lens has been set for you. Do not change this distance. illuminated d triangle screen u lens ho Fig. 1.1 (a) (i) Carefully measure u and record the value. u = ............................................ (ii) Place the screen near the lens. Move the screen away from the lens until a sharp image of the triangle is seen on the screen. (iii) Carefully measure d, the distance between the illuminated triangle and the screen, and record the value. d = ............................................ (iv) Calculate a value m for the magnification, using your answers to (a)(i) and (a)(iii), d – u and the equation m = –––– . u m = ............................................ [2] (b) (i) Measure ho, the height of the illuminated triangle, and record the value. ho = ............................................ (ii) Measure hi, the height of the sharp image on the screen, and record the value. hi = ............................................ (iii) Calculate M, another value for the magnification, using your answers to (b)(i) and hi (b)(ii), and the equation M = –– . ho M = ............................................ [2] (c) A student says that the values of m and M should be the same. For Examiner’s State whether or not your findings support this. Justify your answer by reference to your Use results for m and M. statement ......................................................................................................................... .......................................................................................................................................... justification ....................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... [2] (d) (i) In the space below, sketch the sharp image seen on the screen. (ii) Describe one difficulty you might have found when measuring the height of this image. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. [2] (e) State two precautions which you took to make the experiment reliable. 1. ...................................................................................................................................... .......................................................................................................................................... 2. ...................................................................................................................................... .......................................................................................................................................... [2] [Total: 10]

Mark scheme: 1 (a) u and d recorded in consistent units [1] correct calculation of m and no unit [1] (b) h0 and h1 recorded and M calculated [1] within 10% of m [1] (c) statement matching results (expect ‘Yes’, Yes if < 10%, No if > 10%) [1] justification matching statement (expect ‘within the range of experimental accuracy’ o.w.t.t.e. if ‘No’ expect ‘outside range of experimental accuracy’ o.w.t.t.e.) [1] (d) inverted triangle [1] edges blurred / hand in way of light [1] (e) two suitable precautions, e.g. darkened room / brighter lamp / lights not interfering mark position of lens on holder object and lens same height above bench ruler fixed to bench all apparatus vertical / right angles to bench move screen back and forth (for sharp image) repeats (to obtain average) [2] [Total: 10]

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2 In this experiment, you will investigate how water cools. For Examiner’s The thermometers have been set up in the clamps for you. Do not adjust the heights of the Use thermometers. Carry out the following instructions, referring to Fig. 2.1. thermometer stand hot water Fig. 2.1 (a) (i) Pour hot water into the beaker until it just covers the bulb of the upper thermometer. Do not stir the water for the rest of the experiment. (ii) Wait for about 30 seconds before taking any measurements. (iii) Start the stopclock and read both thermometers. In the top row of Table 2.1, record these temperatures. (iv) Record in the table the temperature θ of each thermometer at 1 minute intervals until time t = 6 minutes. (v) Complete the column headings in the table. Table 2.1 thermometer bulb near thermometer bulb near the bottom of the beaker the surface of the water t / min θ / θ / 0 1 2 3 4 5 6 [4] (b) State in which position of the thermometer bulb the average rate of cooling is the greater. For Justify your answer by referring to your results. Examiner’s Use position ............................................................................................................................ justification ....................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... [2] (c) What precaution do your results suggest should be taken when measuring the temperatures of liquids? Explain how your results show that this is a sensible precaution. precaution ........................................................................................................................ .......................................................................................................................................... explanation ...................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... [2] (d) Another IGCSE student wants to repeat your experiment in order to check the results. Suggest two experimental conditions which should be kept the same. 1. ...................................................................................................................................... .......................................................................................................................................... 2. ...................................................................................................................................... .......................................................................................................................................... [2] [Total: 10]

Mark scheme: 2 (a) table: units correct (symbols or words) [1] θ near bottom of beaker decreasing [1] θ near surface decreasing [1] θ near surface – smaller/same change in 6 min compared to θ near bottom [1] (b) statement matching results and justification matching statement (words or figures) with specific mention of temperature change [1] in same time [1] (if ‘no significant difference’, need mention of ‘within limits of experimental accuracy’ o.w.t.t.e.) (c) appropriate precaution: e.g. stir before reading / keep thermometer at same depth [1] matching explanation: e.g. ensure temperature is the same throughout / temperature different at different depths [1] IGCSE – May/June 2013 0625 53 (d) appropriate precautions relating to comparison any two from: same size / thickness / surface area of beaker same volume of water same initial temperature of water same room temperature / appropriate environmental condition [2] IGNORE same thermometer / type of thermometer [Total: 10]

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3 In this experiment, you will investigate the resistance of electric circuits with lamps connected For in different combinations. Examiner’s Use The apparatus has been set up for you as shown in Fig. 3.1. power supply circuit 1 A A B Fig. 3.1 (a) On Fig. 3.1, draw the symbol for a voltmeter, connected to measure the potential difference between A and B. [1] (b) (i) Connect your voltmeter to the apparatus to measure the potential difference V between A and B. (ii) Switch on. Measure, and record in Table 3.1, the potential difference V and the current I shown by the ammeter. Switch off. Table 3.1 circuit V / I / R / 1 2 3 [5] (c) (i) Reconnect the lamps between A and B as shown in Fig. 3.2. For Examiner’s (ii) Repeat steps (b)(i) and (b)(ii) for circuit 2. Use power supply circuit 2 A A B L Fig. 3.2 (d) (i) Reconnect the lamps between A and B as shown in Fig. 3.3. (ii) Repeat steps (b)(i) and (b)(ii) for circuit 3. power supply circuit 3 A A B Fig. 3.3 (e) Calculate, and record in the table, the total resistance R of each combination of the lamps, using the equation R = . V–I (f) Complete the column headings in the table. Question 3 continues on the next page. (g) If each of the lamps has the same resistance, the total resistance of the lamps in For circuit 3 should be twice the total resistance of the lamps in circuit 1. Examiner’s Use State whether your findings show this to be the case. Justify your answer by reference to your results. statement ......................................................................................................................... .......................................................................................................................................... justification ....................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... [2] (h) The resistance of a lamp is significantly affected by the temperature of its filament. Explain whether this might have affected the results of the experiment. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[1] (i) An IGCSE student wants to measure the potential difference across the lamp marked L in circuit 2. On the diagram for circuit 2, Fig. 3.2, show how a voltmeter should be connected to measure this potential difference. [1] [Total: 10] Turn over for Question 4

Mark scheme: 3 (a) correct symbol for voltmeter [1] (b–d) p.d. < 3.0 V and to at least 1 d.p. [1] current < 1.00 A and to at least 2 d.p. [1] (e) R calculations correct [1] consistent 2/3 sig. figs. in R column [1] (f) units all correct (symbols or words) [1] (g) statement matches results (expect ‘No’, No if > 10%, Yes if < 10%) and R figures quoted appropriately [1] matching statement (need to see too different o.w.t.t.e.) [1] (h) yes, as lamps are at different brightness (o.w.t.t.e.) [1] (i) correct parallel connection [1] [Total: 10]

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4 In this experiment, you will investigate the oscillations of a pendulum. For Examiner’s (a) Carry out the following instructions, referring to Figs. 4.1 and 4.2. The pendulum has Use already been set up for you. clamp bob h B A one complete oscillation Fig. 4.1 Fig. 4.2 (i) Measure, and record in the first row of Table 4.1, the height h of the pendulum bob above the bench. (ii) Pull the pendulum bob a small distance to one side, as shown in Fig. 4.2, and release it. It will oscillate backwards and forwards between A and B, as shown in Fig. 4.2. One complete oscillation is from A to B and back to A. Measure the time t for 10 complete oscillations. Record this value in the table. Table 4.1 h / cm t / s T / s T 2 / s2 (iii) Without changing the height of the clamp, adjust the string to shorten the pendulum by approximately 10 cm. Repeat steps (a)(i) and (a)(ii). (iv) Repeat step (a)(iii) to obtain 3 more sets of readings. [2] (b) (i) For each value of height h, calculate the time T for one complete oscillation using For the equation T = t–– . Examiner’s 10 Use Record these values in the table. (ii) Calculate the values of T 2 and record these in the table. [1] (c) Plot a graph of T 2 / s2 (y-axis) against h / cm (x-axis). [4] (d) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = ........................................[2] (e) Describe a precaution you took in order to measure h as accurately as possible. You For may draw a diagram. Examiner’s Use .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[1] [Total: 10]

Mark scheme: 4 (a) 5 values of h < 60 cm [1] 5 values of t, decreasing with increasing h [1] (b) correct calculations of T and T2 [1] (c) axes labelled [1] appropriate scales (plots occupying at least half grid) [1] plots correct (to ½ square) [1] well judged line, fine plots, thin neat line [1] (d) triangle method seen on graph [1] large triangle (at least ½ line) [1] IGCSE – May/June 2013 0625 53 (e) appropriate precaution e.g. take reading with eye line perpendicular to scale / use set square to ensure rule vertical [1] NOT just ‘parallax’ unless explained [Total: 10]

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