Cambridge IGCSE Physics 0625 — 2008 Oct/Nov Paper 6 · Variant 1

1 An IGCSE student is determining the density of the metal from which a load is made. For Examiner’s The apparatus is shown in Fig. 1.1. Use 0 metre rule spring S0 beaker water bench Fig. 1.1 (a) The student records the scale reading S0 on the metre rule at the bottom of the spring, as shown in Fig. 1.1. S0 = 37.4 cm Describe briefly how the student can avoid a parallax error when taking the scale reading. .......................................................................................................................................... ......................................................................................................................................[1] (b) He then hangs the load on the spring as shown in Fig. 1. 2. He records the new scale For Examiner’s reading S1. Use 0 metre rule spring S1 load bench Fig. 1.2 S1 = 40.5 cm (i) Calculate the extension e1 of the spring using the equation e1 = (S1 – S0). e1 = ...................................................... The student carefully raises the beaker under the load until it is completely under water. The load does not touch the sides or base of the beaker. He records the new scale reading S2. S2 = 39.8 cm (ii) Calculate the extension e2 of the spring using the equation e2 = (S2 – S0). e2 = ...................................................... [2] (c) Calculate the density ρ of the material of the load using the equation For e1 Examiner’sUse ρ = × k (e1 – e2) where k = 1.00 g/cm3. ρ = ...................................................[3] (d) A second load, made from the same material and with the same mass, is too long to be completely submerged in the water. Suggest whether (i) the value obtained for e2 would be greater, smaller or the same as that obtained in part (b) (ii), .................................................................................................................................. (ii) the value obtained for ρ would be greater, smaller or the same as that obtained in part (c). .................................................................................................................................. [2] [Total: 8]

Mark scheme: 1 (a) view perpendicular to (or straight in front of rule)/use of set square [1] (b) (i) correct e1 value 3.1 and correct e2 value 2.4 [1] e in cm [1] (c) density 4.43 (ecf) [1] 2/3 significant figures [1] g/cm3 [1] (d) e2 greater [1] ρ greater (or identical to e2 answer) (ecf) [1] [Total: 8]

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2 The IGCSE class is investigating the potential difference across, and the current in, wires. For Examiner’s The apparatus is shown in Fig. 2.1. Use power source A V S A B C D Fig. 2.1 (a) Draw a circuit diagram of the apparatus. Use standard circuit symbols. (The circuit includes two identical resistance wires AB and CD. Use the standard symbol for a resistance to represent each of these wires.) This circuit is called circuit 1. [3] For circuit 1, the student places the contact S on the resistance wire AB at a distance of For 0.500 m from A. He measures the p.d. V across the wire between A and S and the current I Examiner’s in the circuit. Use The student then records the measurements for circuits 2 and 3, shown in Fig. 2.2 and Fig. 2.3. power source A V S A B C D circuit 2 Fig. 2.2 power source A V S A B C D circuit 3 Fig. 2.3 The voltage V and current I for all three circuits are shown in Table 2.1. For Examiner’s Table 2.1 Use Circuit V / I / 1 0.83 0.53 2 0.75 0.95 3 0.41 0.28 (b) Complete the column headings in the table. [1] (c) Theory suggests that, 1. in circuits 1 and 2, the values of potential difference V will be equal, 2. the value of potential difference V in circuit 3 will be half that in circuit 1 or circuit 2. (i) State whether, within the limits of experimental accuracy, the results support these predictions. Justify your statement by reference to the results. Prediction 1 ............................................................................................................... .................................................................................................................................. Prediction 2 ............................................................................................................... ..............................................................................................................................[2] (ii) Suggest one reason, other than a change in temperature of the wires, why the results may not support the theory. .................................................................................................................................. ..............................................................................................................................[1] [Total: 7]

Mark scheme: 2 Diagram: correct symbols for ammeter and voltmeter [1] correct symbols for resistor [1] correct circuit arrangement [1] Table: units V, A (symbol/word) [1] (c) Prediction 1 Yes – close enough (or words to that effect) OR No – not close enough (or words to that effect) [1] Prediction 2 Yes – approximately half (or words to that effect) [1] Resistance at connections Internal resistance of source/other sensible suggestion [1] [Total: 7]

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3 The IGCSE class is investigating the change in temperature of hot water as cold water is For added to the hot water. Examiner’s Use A student measures and records the temperature θ of the hot water before adding any of the cold water available. He then pours 20 cm3 of the cold water into the beaker containing the hot water. He measures and records the temperature θ of the mixture of hot and cold water. He repeats this procedure four times until he has added a total of 100 cm3 of cold water. The temperature readings are shown in Table 3.1. V is the volume of cold water added. Table 3.1 V / θ/ 0 82 68 58 50 45 42 (a) (i) Complete the column headings in the table. (ii) Enter the values for the volume of cold water added. [2] (b) Use the data in the table to plot a graph of temperature (y-axis) against volume (x-axis). For Draw the best-fit curve. Examiner’s Use [4] (c) During this experiment, some heat is lost from the hot water to the surroundings. Also, each time the cold water is added, it is added in quite large volumes and at random times. Suggest two improvements you could make to the procedure to give a graph that more accurately shows the pattern of temperature change of the hot water, due to addition of cold water alone. 1. ..................................................................................................................................... .......................................................................................................................................... 2. ..................................................................................................................................... ......................................................................................................................................[2] [Total: 8]

Mark scheme: 3 Table θ in °C, V in cm3 [1] correct V 0, 20, 40, 60, 80, 100 [1] Graph: axes labelled with symbol and unit [1] axes suitable (e.g. not ‘3’ scale) and plots occupy more than ½ grid [1] all plots correct (better than ½ sq) [1] well judged, thin best fit line [1] (c) 1. sensible comment about heat loss to the surroundings, e.g. use of insulation/lid [1] 2. sensible comment about adding water in a regulated, timed flow (including smaller volumes/set time intervals/shorter intervals [1] [Total: 8] IGCSE – October/November 2008 0625 6

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4 An IGCSE student is determining the focal length of a converging lens. For The apparatus is shown in Fig. 4.1. Examiner’s Use screen x y lens illuminated object Fig. 4.1 (a) The student places the lens at a distance x = 25.0 cm from the illuminated object. She places the screen close to the lens and then moves it away from the lens until a sharply focused image is formed on the screen. She measures and records the distance y between the lens and the screen. y = 37.1 cm Calculate the focal length f of the lens using the equation xy f = . (x + y) f = ...................................................[2] (b) She then repeats the procedure with the lens at a distance x = 30.0 cm from the illuminated object. Fig. 4.1 shows this position of the apparatus. It is a scale diagram. (i) On Fig. 4.1, measure the distance xs between the lens and the illuminated object. Also on Fig. 4.1, measure the distance ys between the lens and the screen. xs = ...................................................... ys = ...................................................... (ii) Calculate the actual distance y between the lens and the screen. For Examiner’s Use y = ...................................................... (iii) Calculate the focal length f using the new values of x and y. f = ...................................................... (iv) Calculate the average value of f. Show your working. average value of f = ...................................................... [7] (c) The illuminated object has the shape shown below. Draw a diagram to show the appearance of the focused image in (b) on the screen. [1] [Total: 10]

Mark scheme: 4 (a) f = 14.9(4), or 15 [1] correct unit for f [1] (b) (i) xs = 5.0(cm) and ys = 5.2(cm) [1] (ii) factor of ×6 [1] y = 31.2(cm) (ecf) [1] (iii) 15.29, 15.3, 15 (ecf) [1] (iv) correct method [1] 2 or 3 significant figures and correct unit [1] average f 15.1 (correct answer only) [1] (c) inverted image [1] [Total: 10]

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5 (a) Table 5.1 shows some measurements taken by three IGCSE students. The second For column shows the values recorded by the three students. For each quantity, underline Examiner’s the value most likely to be correct. Use The first one is done for you. Table 5.1 Quantity measured Recorded values The mass of a wooden 0.112 kg metre rule 1.12 kg 11.2 kg The weight of an empty 250 cm3 0.7 N glass beaker 7.0 N 70 N The volume of one sheet of this 0.6 cm3 examination paper 6.0 cm3 60 cm3 The time taken for one swing of a 0.14 s simple pendulum of length 0.5 m 1.4 s 14 s The pressure exerted on the ground 0.4 N/cm2 by a student standing on one foot 4.0 N/cm2 40 N/cm2 [4] (b) (i) A student is to find the value of the resistance of a wire by experiment. Potential difference V and current I can be recorded. The resistance is then calculated using the equation R = V/ I. The student knows that an increase in temperature will affect the resistance of the wire. Assuming that variations in room temperature will not have a significant effect, suggest two ways by which the student could minimise temperature increases in the wire during the experiment. 1. .............................................................................................................................. 2. ..........................................................................................................................[2] (ii) Name the circuit component that the student could use to control the current. ..............................................................................................................................[1] [Total: 7]

Mark scheme: 5 (a) 0.7 N [1] 6 cm3 [1] 1.4 s [1] 4.0 N/cm2 [1] (b) (i) minimum current/turn down power supply/increase resistance [1] switch off between readings/carry out without delay [1] (ii) variable resistor/rheostat [1] [Total: 7]

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