Cambridge IGCSE Physics 0625 — 2020 May/June Paper 5 · Variant 3

1 In this experiment, you will determine the weight of a metre rule. Carry out the following instructions, referring to Fig. 1.1. stand boss forcemeter 10.0 cm mark l 90.0 cm loop of thread mark metre rule boss pivot stand 200 g mass bench Fig. 1.1 (a) (i) Ensure that the 10.0 cm mark on the metre rule is immediately above the pivot and that the metre rule is suspended from the forcemeter at the 90.0 cm mark. The metre rule should always be in this position before taking a reading. Move the 200 g mass to a distance l = 20.0 cm from the pivot as shown in Fig. 1.1. Adjust the height of the clamp holding the pivot so that the metre rule is horizontal. Read, and record in Table 1.1, the forcemeter reading F. Repeat this procedure for values of l = 30.0 cm, 40.0 cm, 50.0 cm and 60.0 cm. Table 1.1 l / cm F / N 20.0 30.0 40.0 50.0 60.0 [2] (ii) Explain how you made sure that the metre rule was horizontal before each reading was taken. You may draw a diagram. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (b) Plot a graph of F / N (y-axis) against l / cm (x-axis). Start your axes from the origin (0,0). [4] (c) (i) From your graph determine F0, the value of F when l = 0. F0 = .................................................... [1] (ii) Calculate the weight WR of the metre rule, using the equation WR = 2 × F0. Give WR to a suitable number of significant figures for this experiment. WR = .................................................... [2] (d) A student carrying out this experiment places the 200 g mass on the metre rule instead of hanging it from the loop of thread. Suggest which of these is likely to be the more accurate method. Explain your answer by reference to the procedure. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11]

Mark scheme: 1(a)(i) five F values increasing 1 all < 5 (N) and to at least 1 decimal place 1 1(a)(ii) ensure distances from bench to rule at both ends are equal OR use set square between rule and stand OR align with known horizontal line (e.g. window ledge) 1 1(b) graph: • axes labelled with quantity and unit 1 • appropriate scales (plots occupying at least 1 2 grid) 1 • plots all correct to 1 2 small square and precise plots 1 • well judged line and thin line 1 1(c)(i) F0 correct from graph 1 1(c)(ii) WR in range 0.70 to 4.0 1 2/3 sig figs and unit – N 1 1(d) loop more accurate and can be placed at precise mark (owtte) / difficult to locate centre of block with other method 1

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2 In this experiment, you will investigate a circuit containing different combinations of resistors. The circuit has been set up for you. Carry out the following instructions, referring to Fig. 2.1. power supply A V P Q Fig. 2.1 (a) (i) Switch on. Measure the potential difference V1 and the current I1 in the circuit. V1 = .......................................................... I1 = .......................................................... [1] Switch off. V1 (ii) Calculate a resistance R1 using your values from (a)(i) and the equation R1 = . I1 R1 = .................................................... [1] (b) (i) Connect both resistors in series between terminals P and Q as shown in Fig. 2.2. P Q Fig. 2.2 Switch on. Measure the potential difference V2 and the current I2 in the circuit. V2 = .......................................................... I2 = .......................................................... [1] Switch off. V2 (ii) Calculate a resistance R2 using your values from (b)(i) and the equation R2 = . (I2 × 2) R2 = .................................................... [1] (c) (i) Connect both resistors in parallel between terminals P and Q as shown in Fig. 2.3. P Q Fig. 2.3 Switch on. Measure the potential difference V3 and the current I3 in the circuit. V3 = .......................................................... I3 = .......................................................... [1] Switch off. (V3 × 2) (ii) Calculate a resistance R3 using your values from (c)(i) and the equation R3 = . I3 R3 = .................................................... [1] (d) A student suggests that R1, R2 and R3 should be equal. State whether your results support this suggestion. Justify your statement with reference to your results. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... [2] (e) (i) A student wants to determine R1 by using a variable resistor to control the current in the circuit. Complete the circuit in Fig. 2.4 to show a variable resistor connected for this purpose. You are not required to do this experiment. power supply A V P Q Fig. 2.4 [2] (ii) Briefly explain how using the circuit in Fig. 2.4 will give a more reliable value for R1 than using the procedure you were asked to carry out in (a). ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 11]

Mark scheme: 2(a)(i) V all < 4.00 (V) and to at least 1dp 1 2(a)(ii) correct calculation of R1 1 2(b)(i) I all < 2.00 (A) and to at least 2dp 1 2(b)(ii) units – A, V, Ω 1 Question Answer Marks 2(c)(i) I2 < I1 < I3 1 2(c)(ii) R values all to consistent 2 or consistent 3 significant figures 1 2(d) statement matching results 1 justification matching statement with values from results used, e.g. within limits of experimental accuracy 1 2(e)(i) correct symbol for variable resistor (rectangle with strike-through arrow) 1 in correct complete series circuit 1 2(e)(ii) can obtain average value / plot a graph 1

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3 In this experiment you will determine the focal length of a converging lens. Carry out the following instructions, referring to Fig. 3.1. illuminated triangle u v screen lens bench Fig. 3.1 Method 1 (a) Arrange the apparatus as shown in Fig. 3.1. Place the lens a distance u = 20.0 cm from the illuminated triangle. Place the screen near the lens. Move the screen until a sharp image of the triangle is seen on the screen. (i) Measure the distance v between the lens and the screen as indicated in Fig. 3.1. v = .................................................... [1] (ii) Calculate a value f1 for the focal length of the lens. Use the equation uv f1 = (u + v) . f1 = .................................................... [1] Method 2 (b) Keep the screen in the same position so that the values of u and v are the same as in (a). (i) Move the lens closer to the screen until another sharp image of the triangle is seen on the screen. illuminated triangle u v hO Fig. 3.2 Measure the new distance u between the illuminated triangle and the lens as indicated in Fig. 3.2. u = .......................................................... Measure the new distance v between the lens and the screen. v = .......................................................... [2] (ii) Calculate a second value f2 for the focal length of the lens. Use the equation uv f2 = (u + v) . f2 = .................................................... [1] Method 3 (c) Keep the screen in the same position so that the values of u and v are the same as in (b). (i) Measure hO, the height of the illuminated triangle, as indicated in Fig. 3.2. hO= .......................................................... Measure hI, the height of the image of the triangle on the screen. hI = .......................................................... [1] hI (ii) Calculate a value M for the magnification, using the equation M = . hO M = .................................................... [1] (iii) Calculate a third value f3 for the focal length of the lens. Use your value of v from (b)(i) and the equation v f3 = . (M + 1) f3 = .................................................... [1] (d) State one precaution that you took to ensure that the measurements of u and v in this experiment are as reliable as possible. ................................................................................................................................................... ............................................................................................................................................. [1] (e) (i) Explain why Method 3 is likely to produce a less accurate value for the focal length than Method 1. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Suggest one improvement to make Method 3 more accurate. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 11]

Mark scheme: 3(a)(i) v between 42 cm and 88 cm 1 3(a)(ii) correct calculation of f1 with unit 1 3(b)(i) u within ± 10% of v from (a)(i) 1 v between 18 cm and 22 cm 1 3(b)(ii) f2 and f1 to consistent 2 or consistent 3 significant figures 1 3(c)(i) sensible value for hO and hI < 1.0 (cm) 1 3(c)(ii) correct calculation of M and no unit 1 3(c)(iii) f3 in range 12.0 cm to 18.0 cm 1 Question Answer Marks 3(d) any one from: mark position of lens on holder clamp rule / place rule on bench ensure screen, lens and object all perpendicular view scale perpendicularly 1 3(e)(i) difficult to measure height of image (accurately) as image is small 1 3(e)(ii) use larger object / graph paper on screen OR mark top and bottom of image and measure later 1

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4 A student investigates the factors affecting the electrical output of a solar cell. A solar cell is a device which transforms light energy into electrical energy. Plan an experiment which will enable him to investigate how the potential difference across the terminals of the solar cell varies with the angle of the incident light. You are not required to carry out the experiment. The apparatus available includes: a solar cell as shown in Fig. 4.1 a laboratory lamp. In your plan, you should: • list any additional apparatus needed • state the key variables to be kept constant • explain briefly how to carry out the experiment, including any precautions that must be taken to ensure reliable results • draw a table, 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. You may add to Fig. 4.1 or draw another diagram if it helps to explain your plan. solar cell lamp connecting leads bench Fig. 4.1 .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. ............................................................................................................................................................ [7] [Total: 7]

Mark scheme: 4 MP1 additional apparatus: voltmeter, protractor, metre rule 1 MP2 control variable (one from): distance of lamp from solar panel height of lamp / height of solar panel brightness of lamp 1 MP3 method (one from): measure angle between panel and stand / other fixed datum (switch on lamp) measure potential difference 1 MP4 repeat for different angle 1 MP5 table: appropriate columns with clear headings and units 1 MP6 analysis: suitable analysis of readings, e.g. calculation of rate of change of potential difference with angle draw a suitable graph with correct axes stated 1 Question Answer Marks 4 MP7 additional point / precaution (one from): reading with only ambient light first / subtract ambient light reading make room dark fix protractor keep axis of solar panel and line of lamp perpendicular to each other at least five sets of data taken repeat each reading and take an average repeat for different distance of lamp 1

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