Cambridge IGCSE Physics 0625 — 2018 Oct/Nov Paper 6 · Variant 2

1 A student is determining the spring constant k of a spring. Fig. 1.1 shows the apparatus used. metre rule ‘blu-tack’ between ruler and clamp rod spring l0 clamp stand bench Fig. 1.1 (a) On Fig. 1.1, measure the unstretched length l0 of the coiled part of the spring, in mm. Record this value of length l in Table 1.1 for L = 0.00 N. [1] (b) On Fig. 1.1, show how a set-square could be used to take readings in order to determine the length l0 of the coiled part of the spring. [1] (c) The student places a 0.20 N load on the spring. He records the new length l of the spring in Table 1.1. He repeats the procedure using loads of 0.40 N, 0.60 N, 0.80 N and 1.00 N. All the readings are recorded in Table 1.1. (i) Calculate the extension e of the spring for each value of load L, using the equation e = (l – l0). Record the values of e in Table 1.1. [1] (ii) Complete the column headings in Table 1.1. Table 1.1 L / l / e / 0.00 0 0.20 31 0.40 40 0.60 46 0.80 55 1.00 63 [1] (d) Plot a graph of L / N (y-axis) against e / mm (x-axis). [4] (e) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. (f) The gradient G is numerically equal to the spring constant k. Write down a value for k to a suitable number of significant figures for this experiment. k = .............................................. N / mm [1] [Total: 11]

Mark scheme: 1(a) 1 1(b) recognisable set-square shown from spring to rule along one of the dotted lines 1 1(c)(i) e values 8, 17, 23, 32, 40 1 1(c)(ii) N, mm, mm 1 1(d) Graph: axes correctly labelled and right way round 1 suitable scales, at least ½ the grid used 1 all plots correct to ½ small square 1 good line judgement, thin, continuous line 1 1(e) triangle method used and seen on graph 1 at least half of candidate’s line used 1 1(f) answers within the range 0.025 ± 0.005 (N / mm) and expressed to 2 / 3 significant figures only 1

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2 A student is investigating the power of two lamps. The circuit is shown in Fig. 2.1. A X Y V Fig. 2.1 (a) (i) Record the potential difference (p.d.) VT across the lamps and the current IT in the circuit, as shown in Fig. 2.2 and Fig. 2.3. 4 5 6 0.4 0.6 3 7 2 8 0.2 0.8 1 9 0 10 0 1.0 V A Fig. 2.2 Fig. 2.3 VT = ............................................................... IT = ............................................................... [2] (ii) Calculate the power PT produced by the lamp filaments, using the equation PT = VTIT . PT = ........................................................... [1] (b) The student connects the voltmeter across lamp X only. She records the p.d. VX across lamp X and the current IX in the circuit. 1.3 VX = ............................................................. V 0.18 IX = ............................................................. A She repeats the procedure with the voltmeter connected across lamp Y only. 1.2 VY = ............................................................. V 0.18 IY = ............................................................. A (i) Calculate the power PX produced by the lamp filament X using the equation PX = VXIX, and calculate the power PY produced by the lamp filament Y using the equation PY = VYIY. PX = ................................................................ PY = ................................................................ [1] (ii) State and explain briefly whether the two values for power PX and PY are the same within the limits of experimental accuracy. statement .......................................................................................................................... explanation ........................................................................................................................ ........................................................................................................................................... [2] (c) The student repeats the experiment using two other lamps. She notices that one lamp is dimly lit, but the other lamp does not light at all. The p.d. VT across the lamps is the same as in (b), but the current IT in the circuit is approximately half of the original value. The student concludes that the filament of one of the lamps is broken. State whether you agree with the student and give a reason for your answer. statement .................................................................................................................................. reason ....................................................................................................................................... ................................................................................................................................................... [2] (d) Draw a circuit diagram to show the circuit in Fig. 2.1 rearranged so that: • the lamps are connected in parallel • a variable resistor is connected to control the total current in the circuit • the ammeter will measure the total current in the circuit • the voltmeter will measure the p.d. across the lamps. [3] [Total: 11]

Mark scheme: 2(a)(i) VT = 2.5(0) (V) 1 IT = 0.18(0) (A) 1 2(a)(ii) 0.45 (W) 1 2(b)(i) PX = 0.23, PY = 0.22 and unit W 1 2(b)(ii) statement: Yes idea of within the limits of experimental accuracy 1 explained: e.g. close enough, very close, not too far apart 1 2(c) statement: disagree / no 1 low current not sufficient to make lamp glow / first lamp would not glow with no current / since there is a current (other lamp cannot be broken). 1 2(d) lamps and voltmeter in parallel 1 correct symbols for lamps, ammeter and voltmeter 1 variable resistor, correct symbol and position in a correct circuit 1

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3 A student is determining the refractive index n of the material of a transparent block. Fig. 3.1 shows the outline ABCD of the block. A B D C P3 P4 eye Fig. 3.1 (a) (i) • On Fig. 3.1, draw a normal NL at the centre of side AB. • Continue the normal so that it passes through side CD of the block. [1] (ii) • Label the point F where NL crosses AB. • Label the point G where NL crosses CD. • Draw a line EF at an angle i = 30° to the left of the normal and above side AB. [1] (iii) Mark the positions of two pins P1 and P2 on line EF placed at a suitable distance apart for this type of ray-tracing experiment. [1] (b) The student observes the images of P1 and P2 through side CD of the block. He places two pins P3 and P4 between his eye and the block so that P3, P4 and the images of P1 and P2 seen through the block, all appear exactly one behind the other. The positions of P3 and P4 are marked on Fig. 3.1. • Draw a line passing through P3 and P4. Continue the line until it meets the normal NL. • Label the point J where the line meets the normal. • Label the point H where the line meets side CD. Draw the line FH. [1] (c) (i) Measure and record the length a of the line FH. a = ........................................................... [1] (ii) Measure and record the length b of the line HJ. b = ........................................................... [1] a (iii) Calculate the refractive index n using the equation n = . b n = ........................................................... [2] (d) A student states that repeating the experiment improves the reliability of the value obtained for n. Suggest additional values for the angle of incidence i that you would use when repeating the experiment to improve the reliability. ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [2] (e) State one precaution that you would take in this experiment to obtain accurate results. ................................................................................................................................................... .............................................................................................................................................. [1] [Total: 11]

Mark scheme: 3(a)(i) normal at centre of AB (by eye) produced to cross CD 1 3(a)(ii) i = 30° ± 1° drawn to the left of the normal 1 3(a)(iii) P1 and P2 in air at minimum distance apart of 5.0cm 1 3(b) line through P3 and P4 neat, straight and continued to N 1 3(c)(i) a = 55 ± 1 (mm) 1 3(c)(ii) b = 37 ± 1 mm and both with correct unit 1 3(c)(iii) n within the range 1.42 ± 1.60 if 3 s.f. quoted, or within the range 1.4 to 1.6 if 2 s.f. quoted 1 2 or 3 significant figures with no unit 1 3(d) at least two additional angles suggested 1 between 10(°) and 60(°) inclusive with at least 5(°) difference between values 1 3(e) any one from: large pin separation / pins at least 5 cm apart ensure that the pins are vertical / upright / perpendicular to the paper / placed straight view the bases of the pins use thin pencil lines / thin pins 1

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4 A student is investigating whether the type of container affects the time taken for water to be heated from room temperature to boiling point. The following apparatus is available: 250 cm3 copper can 250 cm3 aluminium can 250 cm3 glass beaker Bunsen burner measuring cylinder thermometer tripod and gauze stopwatch Other apparatus normally available in the school laboratory is also available. Plan an experiment to investigate whether the type of container affects the time taken for water to be heated from room temperature to boiling point. You should: • explain briefly how you would carry out the investigation • state the key variables that you would control • draw a table, or tables, 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: 4 method: MP1 measure room / starting temperature 1 MP2 measure time to raise water temperature to boiling point 1 MP3 repeat with the other two containers 1 control variables: MP4 any two from: same starting temperature / same room temperature same volume / mass / amount of water MP5 keep Bunsen burner flame constant / keep the distance from the flame to the bottom of the beaker constant 2 table: MP6 table to show container and heating time 1 conclusion: MP7 comparison of heating times and suitable comment made 1

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