Cambridge IGCSE Physics 0625 — 2022 May/June Paper 5 · Variant 3

1 In this experiment, you will investigate the forces supporting a metre rule. Carry out the following instructions, referring to Fig. 1.1. Do not attempt to change the position of either newton meter by adjusting the positions of the loops of thread attached to them. clamp newton meter P newton meter Q stand metre rule 10.0 cm mark 90.0 cm mark d loop of thread 1.00 N load bench Fig. 1.1 (a) Move the 1.00 N load to a distance d = 25.0 cm from the 0.0 cm end of the rule. Move one stand slightly, if necessary, so that the newton meters are as near to vertical as possible. Read, and record in Table 1.1, the value FP on newton meter P and the value FQ on newton meter Q. Repeat this procedure for d = 35.0 cm, d = 45.0 cm, d = 55.0 cm and d = 65.0 cm. Table 1.1 d / cm FP / N FQ / N 25.0 35.0 45.0 55.0 65.0 [2] (b) Plot a graph of FP / N (y-axis) against d / cm (x-axis). On the same axes, and using the same scales, plot a graph of FQ / N (y-axis) against d / cm (x-axis). Draw two best-fit lines, one for each set of plots. Show clearly on your graph which line is for FP and which line is for FQ. FP / N FQ / N [5] (c) From your graph, determine F0, the value of FP where the two best-fit lines cross. F0 = ............................................................... Calculate the weight WR of the metre rule, using the equation WR = (2 × F0) – k, where k = 1.00 N. WR = ............................................................... [2] (d) This experiment can be done by moving a clamp to make the rule horizontal before taking each reading. Explain how to make sure that the rule is horizontal. You may draw a diagram. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] (e) A student does the experiment with the same equipment as you. He reads values of FP which are the same as yours but his values of FQ are all higher than yours by 0.10 N. Suggest a reason for this difference. Assume that your values of FP and FQ in Table 1.1 are correct. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11]

Mark scheme: 1(a) 5 FP values decreasing and 5 FQ values increasing 1 all < 3 N and to ⩾ 1 d.p. 1 1(b) graph:  x-axis labelled with quantity and unit 1  suitable scales (plots occupying at least 3 large squares in each direction) 1  plots all correct to ½ small square and precise plots 1  2 well judged lines and thin lines 1  intersection at d = 50.0 cm to 1 small square 1 1(c) F0 present and WR in range 1 (N) to 3 (N) 1 WR expressed to 2 or 3 significant figures and with unit of N 1 1(d) any valid method e.g. check equal distance between rule and bench at two places OR use set square/protractor between stand and rule OR line up with suitable (named) surface 1 1(e) forcemeter Q has zero error OR has not been set to 0 at start 1

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2 In this experiment, you will investigate how the volume of water in a beaker affects the rate at which the water cools. Carry out the following instructions, referring to Fig. 2.1. thermometer stand beaker bench Fig. 2.1 (a) During this experiment, the thermometer must remain clamped securely to the stand. Pour 150 cm3 of hot water into the beaker. Place the thermometer in the water. Wait until the reading on the thermometer stops rising. In the first row of Table 2.1, record the temperature θ of the water at t = 0 and immediately start the stop-clock. Record the temperature θ of the water at times t = 30 s, t = 60 s, t = 90 s, t = 120 s, t = 150 s and t = 180 s. Remove the thermometer from the beaker and tip out the water. [1] (b) (i) Repeat (a) using 50 cm3 of hot water. [2] (ii) Complete the headings in Table 2.1. Table 2.1 beaker beaker with 150 cm3 of hot water with 50 cm3 of hot water t / θ/ θ/ 0 30 60 90 120 150 180 [1] (c) Write a conclusion stating how the volume of water affects the rate of cooling of the water. Justify your answer by reference to your results. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (d) (i) Using your results for 50 cm3 of water, calculate the average cooling rate x for the first 90 s of the experiment. Use your readings from Table 2.1 and the equation θ0 – θ90 x = T where T = 90 s and θ0 and θ90 are the temperatures at t = 0 and t = 90 s. Include the unit for the cooling rate. x = ......................................................... [1] (ii) A student does this experiment in a room with a much higher room temperature than your room. State how this affects her value of x in (d)(i). Explain your answer by reference to your results from the beaker with 50 cm3 of hot water. statement .......................................................................................................................... explanation ........................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... [2] (e) Some thermal energy is lost from the sides of the beaker. Another student wishes to find out how much this loss of thermal energy affects the cooling rate of 50 cm3 of water. Briefly describe an additional experiment that the student can carry out to investigate this. Explain how the results can be used to determine how much this loss affects the cooling rate. You are not required to carry out the experiment. additional experiment ............................................................................................................... ................................................................................................................................................... use of results ............................................................................................................................ ................................................................................................................................................... [2] [Total: 11]

Mark scheme: 2(a) 1 2(b)(i)  for 50 cm3 decreasing and recorded to at least 1 °C 1 decreasing more quickly than  for 150 cm3 1 Question Answer Marks 2(b)(ii) s, °C both correct 1 2(c) statement matching readings in table 1 comparison of temperature changes over 180 s, matching statement 1 2(d)(i) correct calculation of x and unit °C / s 1 2(d)(ii) her value of x will be less/lower 1 cooling rate faster when difference between water temperature and room temperature is greater 1 2(e) repeat experiment with a lid 1 calculate cooling rate and subtract from x to find cooling rate without transfer from sides OR a comparison of cooling rates 1

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3 In this experiment, you will determine the focal length of a converging lens by different methods. Method 1 Carry out the following instructions, referring to Fig. 3.1. (a) Arrange the illuminated object, lens and mirror as shown in Fig. 3.1. D mirror illuminated object f1 lens card bench Fig. 3.1 (i) Set the distance D between the mirror and the illuminated object to 40 cm. Move the lens until a sharp image appears on the front of the card, by the side of the illuminated object. Measure the distance f1 between the lens and the illuminated object. This is a value for the focal length of the lens. f1 = ......................................................... [1] (ii) Briefly describe a technique to obtain an image on the card that is as sharp as possible in this experiment. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] Method 2 Carry out the following instructions, referring to Fig. 3.2. (b) Set up the lens, illuminated object and screen as shown in Fig. 3.2. illuminated object u lens screen hO bench Fig. 3.2 Set the distance between the illuminated object and the lens to u = 20.0 cm. Move the screen until a sharp image of the illuminated object appears on the screen. (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 = ............................................................... [2] hO (ii) Calculate a value W using the equation W = . hI W = ............................................................... Calculate a second value f2 for the focal length of the lens, using the equation u f2 = (W + 1) . f2 = ............................................................... [2] (iii) Describe one difficulty that can be experienced when measuring the height of the image. Suggest an improvement to overcome this difficulty. difficulty ............................................................................................................................. ........................................................................................................................................... improvement ..................................................................................................................... ........................................................................................................................................... [2] (c) A student suggests that f1 and f2 should be equal. State whether your results support this suggestion. Justify your statement by reference to your results. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... [2] (d) Describe one precaution you took to obtain reliable measurements of f1 and u in this experiment. ................................................................................................................................................... ................................................................................................................................................... [1] [Total: 11]

Mark scheme: 3(a)(i) f1 = 13.0 (cm) to 17.0 (cm) 1 3(a)(ii) move lens backwards and forwards slowly OR move lens slowly 1 3(b)(i) hO between 1 (cm) and 2 (cm) 1 hI between 3.2 (cm) and 6.5 (cm) 1 3(b)(ii) W with no unit and f2 expressed to 2 or 3 significant figures with unit cm 1 f2 within 10% of f1 1 3(b)(iii) hand gets in way of light 1 mark on screen and measure later OR use screen with scale OR use translucent screen and measure at rear 1 Question Answer Marks 3(c) statement matching results 1 values within limits of experimental accuracy/owtte and values quoted in justification 1 3(d) any one from: mark position of lens on holder clamp/place rule on bench ensure screen, lens and object all perpendicular view rule perpendicularly repeat and take average use darkened room/brighter light 1

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4 A student investigates the resistance of a light-dependent resistor (LDR). The resistance of an LDR changes as the intensity of light falling on it varies. V The resistance R of the LDR is calculated using the equation R = I where V is the potential difference (p.d.) across the LDR and I is the current in the LDR. Plan an experiment to investigate how the light intensity affects the resistance of an LDR. You are not required to carry out the experiment. The apparatus available includes: an LDR equipment to connect the circuit, part of which is shown in Fig. 4.1 a lamp with a power supply. In your plan, you should: • complete the circuit diagram in Fig. 4.1 to show a voltmeter connected to measure the potential difference across the LDR • state how the light intensity falling on the LDR will be varied and list any additional apparatus needed • explain briefly how to do the experiment, including any precautions taken to ensure reliable results • state one key variable to be kept constant • draw a table, or tables, 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. A power supply LDR Fig. 4.1 .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 MP1 apparatus: voltmeter – correct symbol in parallel with LDR 1 MP2 independent variable: statement identifying the independent variable e.g. light intensity, distance, current, voltage 1 MP3 method: measure independent variable (e.g. metre rule to measure distance between lamp and LDR) measure p.d. and current calculate resistance of LDR 1 MP4 repeat for new value of independent variable 1 MP5 control variable: any variable appropriate to independent variable (e.g. distance from lamp to LDR if current through lamp is the independent variable, p.d., power, intensity) 1 MP6 table: columns, with units, for independent variable, measured dependent variable and resistance (not just resistance without raw measurements) 1 MP7 analysis: compare resistance values (in table) to see if change in independent variable produces change in resistance plot line graph (with axes specified) 1

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