Cambridge IGCSE Physics 0625 — 2017 Oct/Nov Paper 6 · Variant 1

1 A student is investigating resistance using the circuit shown in Fig. 1.1. power supply A RA V Fig. 1.1 (a) The student measures the potential difference V1 across the resistor RA and the current I1 in the circuit. Figs. 1.2 and 1.3 show the voltmeter and ammeter scales. 3 4 5 6 7 0.4 0.6 2 8 0.2 0.8 0 1 910 0 1.0 V A Fig. 1.2 Fig. 1.3 (i) Write down the readings shown on the scales in Figs. 1.2 and 1.3. V1 = ............................................................... I1 = ............................................................... [2] V 1 = . (ii) Calculate the resistance R1 of the resistor RA using the equation R 1 I 1 R1 = .......................................................... [1] (b) The student connects a resistor RB in series with RA. She measures the potential difference V2 across the two resistors RA and RB combined and the current I2 in the circuit. 1.8 V V2 = ............................................................... 0.19 A I2 = ............................................................... Calculate the resistance R2 of resistors RA and RB combined in series, using the equation V 2 R 2 = . I 2 R2 = ...........................................................[1] (c) The student connects a third resistor RC in series with RA and RB. She measures the potential difference V3 across the three resistors and the current I3 in the circuit. 1.7 V V3 = ............................................................... 0.13 A I3 = ............................................................... (i) Calculate the resistance R3 of resistors RA, RB and RC combined in series, using the V 3 = . equation R 3 I 3 R3 = ............................................................... (ii) On Fig. 1.4, draw a line for the needle on the ammeter to show the reading of 0.13 A. 0.4 0.6 0.2 0.8 0 1.0 A [1] Fig. 1.4 (d) A student suggests that R3 = 3 × R1. State whether the results agree with this suggestion. Justify your answer by reference to the results. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... ................................................................................................................................................... [1] (e) Another student suggests that the three resistors RA, RB and RC each have the same value of resistance. Explain how you could use the circuit shown in Fig. 1.1 to check this suggestion. ................................................................................................................................................... ...............................................................................................................................................[1] (f) Complete the circuit diagram in Fig. 1.5 to show: • the three resistors connected in parallel • the voltmeter connected to measure the potential difference across the resistors • a variable resistor connected to control the current in all three resistors. power supply A Fig. 1.5 [2] (g) The circuit in Fig. 1.5 could be used to determine the combined resistance of three resistors connected in parallel. Suggest a reason for connecting a variable resistor in the circuit. ................................................................................................................................................... ...............................................................................................................................................[1] [Total: 10]

Mark scheme: 1(a)(i) 1.8 (V) 1 0.38 (A) 1 1(a)(ii) R1 4.74 (4.737, 4.7) 1 1(b) R2 = 9.47 OR 9.5 (2 or 3 significant figures required) 1 1(c) Pointer at 0.13 1 1(d) Statement YES or NO (owtte) Justification to include the idea of within (or beyond, ecf) the limits of experimental accuracy, matching the statement 1 1(e) Determine each resistance in turn 1 1(f) Three resistors in parallel, ONE voltmeter in parallel with resistors and correct symbols for voltmeter and resistors 1 Variable resistor in series with the supply, correct symbol in a correct circuit 1 1(g) Repeat with different currents OR to obtain a range of readings 1

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2 A student is determining the focal length f of a lens. Fig. 2.1 shows the apparatus used. d illuminated object u v screen lens bench Fig. 2.1 (a) The student obtains a sharply-focused image on the screen. (i) On Fig. 2.1, measure the distance v from the lens to the screen. v = ............................................................... (ii) On Fig. 2.1, measure the distance d from the illuminated object to the screen. d = ............................................................... [2] (b) Fig. 2.1 is drawn 1/10th actual size. (i) Calculate V, the actual distance from the lens to the screen. Record the value of V in the first row of Table 2.1. (ii) Calculate D, the actual distance from the illuminated object to the screen. Record the value of D in the first row of the table. (iii) Calculate UV and record the result in the table. [2] (c) The student repeated the procedure with the lens at a distance U = 30.0 cm from the illuminated object. All the readings are recorded in the table. Table 2.1 U / cm V / cm UV / cm2 D / cm 20.0 30.0 29.5 885 59.5 State one difference that you would expect to observe between the image formed on the screen when U = 20.0 cm and when U = 30.0 cm. ................................................................................................................................................... ...............................................................................................................................................[1] (d) (i) Use the results in the first row of the table to calculate a value f1 for the focal length of the UV = . lens. Use the equation f1 D f1 = ............................................................... (ii) Use the results in the second row of the table to calculate a value f2 for the focal length of UV = . the lens. Use the equation f2 D f2 = ............................................................... (iii) Calculate the average value fA for the focal length of the lens. Give your answer to a suitable number of significant figures for this experiment. fA = ............................................................... [3] (e) Suggest two reasons why it may be difficult to obtain reliable results in this experiment. 1. ............................................................................................................................................... ................................................................................................................................................... 2. ............................................................................................................................................... ................................................................................................................................................... [2] (f) A student states that a more reliable value for the focal length is obtained if more values of U, V and D are collected, enabling a graph to be drawn of UV against D. (i) Suggest a suitable number of values for U. ........................................................................................................................................... (ii) Suggest a suitable range of values for U. ........................................................................................................................................... [2] [Total: 12]

Mark scheme: 2(a)(i),(ii) v = 6.(0) AND d = 8.(0) or v = 60 AND d = 80 1 correct matching unit 1 2(b)(i),(ii),(iii) V = 60 cm (or 10 × candidate’s v) and D = 80 cm (or 10 × candidate’s d) 1 UV 1200 (ecf) 1 2(c) One from: Different size Different brightness Sharpness / clearness / coloured edges 1 2(d)(i),(ii),(iii) f values 15(.0) and 14.9 (14.87) 1 fA correct method 1 2 or 3 significant figures 1 2(e) Any two from: Difficulty deciding exact position of sharpest image Difficulty measuring to centre of lens Product uv increases problem Image edges blurred / not clear Insufficient sets of results 2 2(f)(i) 5 – 10 1 2(f)(ii) Difference of at least 40 cm with a range 15–100 1

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3 A student is investigating whether the diameter of a pendulum bob affects the period of a pendulum. The period is the time taken for one complete oscillation of the pendulum. Fig. 3.1 shows a pendulum. Fig. 3.2 shows one complete oscillation. stand clamp thread bob one complete oscillation Fig. 3.1 Fig. 3.2 The student has the following apparatus: pendulum bobs made of polystyrene with diameters 1 cm, 2 cm, 3 cm, 4 cm and 5 cm a supply of thread and a pair of scissors clamp and stand. Plan an experiment to investigate whether the diameter of a pendulum bob affects the period of a pendulum. You should: • list additional apparatus that you would require • explain briefly how you would carry out the investigation • state the key variables that you would control • draw a table with column headings, to show how you would display your readings (You are not required to enter any readings in the table.) • explain briefly how you would use your readings to reach a conclusion. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[7] [Total: 7]

Mark scheme: 3 MP1 Stopwatch (or equivalent) AND (metre) rule / ruler 1 MP2 Measure time for 5 (+) oscillations 1 MP3 Divide by number of oscillations to find period (T) 1 MP4 Repeat for each bob 1 MP5 Variable; one from: Initial amplitude / starting position Length of pendulum / thread Number of oscillations 1 MP6 Table with column headings for t, or period (T), or both AND d, with correct units 1 MP7 Conclusion: Plot graph(s) of d against period (T) or t (or vice versa) OR compare period (T) or t values for different diameters 1

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4 A student is determining the weight of a load using a balancing method. Fig. 4.1 shows the apparatus used. metre rule P Q a b bench pivot Fig. 4.1 The student places the metre rule on the pivot and adjusts its position so that the metre rule is as near as possible to being balanced. He places a load P on the metre rule so that its centre is exactly at the 30.0 cm mark. He records the distance a between P and the pivot. 19.8 cm a = ............................................................... He places a load Q of weight Q = 1.0 N on the metre rule and adjusts the position of Q so that the metre rule is as near as possible to being balanced. He measures the distance b between the centre of load Q and the pivot. He repeats the procedure, with the load P remaining at the 30.0 cm mark, using Q values of 2.0 N, 3.0 N, 4.0 N and 5.0 N. All the readings are recorded in Table 4.1. Table 4.1 Q / N b / cm 1 1 Q N 1.0 40.0 2.0 19.5 3.0 13.5 4.0 10.5 5.0 7.5 1 (a) For each value of Q, calculate and record the result in the table. [1] Q 1 1(b) Plot a graph of b / cm (y-axis) against (x-axis). Q N [4] (c) (i) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = ...........................................................[2] G (ii) Calculate the weight P of load P using the equation P = , where a = 19.8 cm. a P = ...........................................................[1] (d) The student measures the weight P of load P using a forcemeter. Fig. 4.2 shows the forcemeter. N 0.0 1.0 2.0 load P Fig. 4.2 Write down the reading P shown on the forcemeter. P = ....................................................... N [1] (e) The student has carried out the experiment with care and is expecting the two values of P in (c) and (d) to be the same. Suggest two reasons why the values of P may be different. 1. ............................................................................................................................................... ................................................................................................................................................... 2. ............................................................................................................................................... ................................................................................................................................................... [2] [Total: 11]

Mark scheme: 4(a) 1 / Q values 1.(0), 0.5(0), 0.33(3), 0.25, 0.2(0) 1 4(b) Graph: Axes correctly labelled and right way round 1 Suitable scales 1 All 5 plots correct to ½ small square 1 Good line judgement, thin, continuous line 1 4(c)(i),(ii) At least half line used for triangle method 1 Clearly shown on graph 1 P = 1.8 – 2.2 (N) 1 4(d) 1.9 1 4(e) Two from: Difficulty in obtaining balance Difficulty in judging centre of loads Loads may slip / slide Forcemeter not sensitive Forcemeter zero error 2

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