Cambridge IGCSE Physics 0625 — 2018 Oct/Nov Paper 5 · Variant 2

1 In this experiment, you will determine the spring constant k of a spring. Carry out the following instructions, referring to Fig. 1.1. metre rule ‘blu-tack’ between ruler and clamp rod spring l0 clamp stand bench Fig. 1.1 (a) The metre rule is fixed in position close to the spring. Do not change the position of the metre rule. (i) Use the set-square provided to take readings from the metre rule in order to determine the length l0 of the coiled part of the spring. Record of readings taken .................................................................................................. .......................................................................................................................................[1] (ii) Record in Table 1.1 the value of the length of the spring l0 when the load L is 0.00 N. [1] (iii) • Place a load of 0.20 N on the spring. Record in Table 1.1 the new length l of the spring. • Use the equation e = (l – l0) to calculate the extension e of the spring. Record the value of e in the table. • Repeat the procedure using loads of 0.40 N, 0.60 N, 0.80 N and 1.00 N. Record all the readings and results in the table. Table 1.1 L / N l / mm e / mm 0.00 0 0.20 0.40 0.60 0.80 1.00 [2] (b) Plot a graph of L / N (y-axis) against e / mm (x-axis). [4] (c) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = ...........................................................[2] (d) 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)(i) two scale readings recorded 1 1(a)(ii) l0 = difference between the two scale readings recorded in the table 1 1(a)(iii) increasing values of l in table 1 correct e values 1 1(b) graph: axes correctly labelled and right way round 1 suitable scales 1 all plots correct to ½ small square 1 good line judgement, thin, continuous line 1 1(c) triangle method used and seen on graph 1 at least half of candidate’s line used 1 1(d) k correct to 2 or 3 significant figures 1

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2 In this experiment, you will investigate the power of lamps. The circuit shown in Fig. 2.1 has been set up for you. A X Y V Fig. 2.1 (a) (i) Switch on. Measure and record the potential difference (p.d.) VT across the lamps and the current IT in the circuit. Switch off. VT = ............................................................... IT = ............................................................... [2] (ii) Calculate the power PT produced by the lamp filaments, using the equation PT = VT IT . PT = ...........................................................[1] (b) Disconnect the voltmeter. Reconnect the voltmeter across lamp X. Switch on. (i) Measure and record the potential difference (p.d.) VX across lamp X and the current IX in the circuit. Switch off. VX = ............................................................... IX = ............................................................... [1] (ii) Calculate the power PX produced by the lamp filament using the equation PX = VX IX. PX = ...........................................................[1] (c) Disconnect the voltmeter. Reconnect the voltmeter across lamp Y. Switch on. (i) Measure and record the potential difference VY across lamp Y and the current IY in the circuit. Switch off. VY = ............................................................... IY = ............................................................... [1] (ii) Calculate the power PY produced by the lamp filament using the equation PY = VY IY. PY = ...........................................................[1] (d) State and explain briefly whether your two values for power, PX and PY are the same within the limits of experimental accuracy. statement .................................................................................................................................. explanation ............................................................................................................................... ................................................................................................................................................... [2] (e) Draw a circuit diagram to show the circuit rearranged so that: • the lamps are connected in parallel • the ammeter will measure the total current in the circuit • the voltmeter will measure the p.d. across the lamps. You are not asked to set up this circuit. [2] [Total: 11]

Mark scheme: 2(a)(i) VT to at least 1 d.p. and < 4 V 1 IT to at least 2 d.p. and < 1 A 1 2(a)(ii) PT correct 1 2(b)(i) VX < VT and IX present 1 2(b)(ii) PX present and units V, A and W 1 2(c)(i) VY < VT and I2 present 1 2(c)(ii) PY present and PX + PY = PT within 10% 1 2(d) statement matches results 1 idea of within (or beyond) limits of experimental accuracy explained, e.g. close enough, very close, too far apart 1 2(e) lamps and voltmeter in parallel 1 correct symbols for lamps, ammeter and voltmeter in correct circuit 1

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3 In this experiment, you will determine the refractive index n of the material of a transparent block. E hole N A F B D G C L eye Fig. 3.1 (a) Carry out the following instructions, using the separate ray-trace sheet provided. Refer to Fig. 3.1 for guidance. • Place the transparent block, largest face down, on the ray-trace sheet supplied. The block should be approximately in the middle of the paper. • Draw and label the outline of the block ABCD. • Remove the block and draw the normal NL at the centre of side AB. Continue the normal so that it passes through side CD of the block. • Label the point F where NL crosses AB. • Label the point G where NL crosses CD. [2] (b) • Draw the line EF at an angle i = 30° to the normal as shown in Fig. 3.1. • Place the paper on the pin board. • Place two pins P1 and P2 on line EF at a suitable distance apart for this experiment. • Replace the block and look from the position of the eye shown in Fig. 3.1, to observe the images of P1 and P2 through side CD of the block. Adjust your line of sight until the images of P1 and P2 appear one behind the other. • Place two pins P3 and P4 between your eye and the block so that P3, P4, and the images of P1 and P2, seen through the block, appear one behind the other. • Label the positions of P1, P2, P3 and P4. • Remove the block and the pins. • Draw a line joining the positions of P3 and P4. Continue the line until it meets the normal NL. • Label the point J where the line meets the normal NL. • 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) Repeat the procedure in (b) using the angle of incidence i = 40°. (i) Repeat the measurements in (c) for i = 40°. a = ............................................................... b = ............................................................... [1] a (ii) Calculate the refractive index n using the equation n = b n = ...........................................................[1] (e) A student carries out this experiment with care and expects the two values of refractive index n obtained in this experiment to be equal. State two difficulties with this type of experiment that could account for any difference in the two values of n. 1. ............................................................................................................................................... ................................................................................................................................................... 2. ............................................................................................................................................... ................................................................................................................................................... [2] [Total: 11] Tie your ray-trace sheet into this Question Booklet between pages 8 and 9.

Mark scheme: 3(a) ray-trace: normal through block 1 normal at centre of AB 1 3(b) ray-trace: P1 and P2 at minimum distance apart of 5.0 cm 1 3(c)(i) a correct to ± 1 mm 1 3(c)(ii) b correct to ± 1 mm and both with correct unit 1 3(c)(iii) n correct, 2 or 3 significant figures with no unit 1 n = 1.4 to 1.6 1 3(d)(i) second set of lines seen on trace in approximately the correct positions and a and b recorded 1 3(d)(ii) n within 10% of value in (b) 1 3(e) any two from: lining up the pins exactly / seeing pins clearly drawing accurate, thin lines getting pins vertical / bent pins placing block accurately on drawn outline / the outline is larger than the block 2

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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 used 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 are not required to carry out this investigation. 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 the 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 / same distance from flame to bottom of beaker 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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