Cambridge IGCSE Physics 0625 — 2023 Oct/Nov Paper 6 · Variant 1

1 A student determines the weight of a metre ruler using a balancing method. Fig. 1.1 shows the set-up. P metre ruler a b 90.0 cm pivot bench Fig. 1.1 (a) The student places the metre ruler on the pivot. She places a load P on the metre ruler at the 90.0 cm mark. She adjusts the position of the metre ruler on the pivot so that the metre ruler is as near as possible to being balanced. The ruler balances with the pivot at the 75.0 cm mark. Calculate the distance a from the 90.0 cm mark to the pivot. Record the value of a in the first row of Table 1.1. [1] (b) She records, in Table 1.1, the distance b from the pivot to the 0.0 cm end of the metre ruler. She repeats the procedure placing the load P at the 85.0 cm mark, 80.0 cm mark, 75.0 cm mark and 70.0 cm mark. She records the values of a and b in Table 1.1. Table 1.1 a / cm b / cm 75.0 13.1 71.9 11.3 68.8 9.4 65.6 7.5 62.5 Plot a graph of a / cm (y-axis) against b / cm (x-axis). Start the y-axis at a = 0.0 cm. Start the x-axis at a suitable value for the results. Draw the best-fit line. [4] (c) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = ......................................................... [2] (d) The weight W of the metre ruler is numerically equal to 2G. Calculate the weight W of the metre ruler. W = ......................................................... [2] (e) Suggest one practical reason why it is difficult to obtain accurate readings for a and b. ................................................................................................................................................... ............................................................................................................................................. [1] (f) Using only the apparatus provided for the experiment, explain briefly how you would determine the position of the centre of mass of the metre ruler. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11]

Mark scheme: Question Answer Marks 1(a) a = 15(.0) 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) Method shown clearly on graph 1 Triangle using at least ½ of candidate’s line between extreme plots. 1 1(d) W = 2G with unit N 1 W in range 1.0–1.4 1 1(e) Difficult to obtain exact balance 1 OR difficult to judge position of (centre of) load OR load / ruler may slide 1(f) Balance rule on pivot, balance point is at centre of mass / Find where the rule balances. 1

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2 A student investigates the resistance of a resistance wire. Fig. 2.1 shows the circuit that he uses. A l B sliding resistance wire contact C V Fig. 2.1 (a) The student places a sliding contact C at a distance l = 20.0 cm from B. He measures the potential difference (p.d.) V across length l of the resistance wire. He measures the current I in the circuit. The meters are shown in Fig. 2.2 and Fig. 2.3. 0.4 0.6 2 3 0.2 0.8 1 4 0 1.0 0 5 A V Fig. 2.2 Fig. 2.3 Table 2.1 R l / V / R / / l 20.0 60.0 1.6 2.1 0.035 100.0 2.5 3.3 0.033 (i) Write down the current I shown on the student’s ammeter. I = ......................................................... [1] (ii) Record the potential difference V shown on the student’s voltmeter in the first row of Table 2.1. [1] (iii) Calculate, and record in Table 2.1, the resistance R of 20.0 cm of the resistance wire. V Use the equation R = . [1] I R (iv) Calculate, and record in the first row of Table 2.1, for l = 20.0 cm. [1] l (v) Complete the column headings in Table 2.1. [2] (b) The student repeats the procedure using l = 60.0 cm and l = 100.0 cm. The readings and results are shown in Table 2.1. R Look carefully at the values of in Table 2.1. l (i) Write a conclusion about the relationship between R and l. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Justify your conclusion by reference to the results. ........................................................................................................................................... ..................................................................................................................................... [1] (c) Use the values in Table 2.1 to estimate the resistance R2 of 2.000 m of the resistance wire. Show your working. R2 = ......................................................... [3] [Total: 11]

Mark scheme: 2(a)(i) I = 0.76(A) 1 2(a)(ii) V = 0.5 1 2(a)(iii) R = 0.7, 0.66 or 0.658 1 2(a)(iv) R / l = 0.035 or 0.033 1 2(a)(v) cm, V,  1  / cm 1 2(b)(i) Conclusion to match results. Expect R increases as l increases / (directly) proportional / R / l constant 1 2(b)(ii) Justification matching conclusion with clear reference to the results. 1 2(c) Correct method (e.g. doubling the 100 cm value, or taking average R / L or 0.033 then multiply by length) 1 Correct answer 1 Answer quoted to one or two significant figures 1

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3 A student investigates the magnification of the image produced by a lens. Fig. 3.1 shows the set-up. illuminated object u v screen lens bench Fig. 3.1 hO Fig. 3.2 (a) On Fig. 3.2, measure the height hO of the illuminated object. hO = ......................................................... [2] (b) Fig. 3.1 is drawn to 1/10th scale. (i) On Fig. 3.1 measure the distance u. u = ......................................................... [1] (ii) The actual object distance U is 20.0 cm. • The student places the lens at the distance U = 20.0 cm from the illuminated object. • He moves the screen slowly until a clearly focused image is formed on the screen. • He measures the distance V between the centre of the lens and the screen. On Fig. 3.1, this distance is represented to scale by the distance v. Use Fig. 3.1 to determine the actual distance V between the centre of the lens and the screen. Show your working. V = ......................................................... [2] V (iii) Calculate, and record in Table 3.1, the magnification m using the equation m = U. [1] (iv) The student measures the height of the image hI that is formed on the screen. The reading is shown in Table 3.1. hI Calculate, and record in Table 3.1, the ratio . hO Table 3.1 hI U / cm V / cm m hI / cm hO 20.0 5.9 30.0 34.8 1.16 1.8 1.2 [1] (c) The student repeats the procedure using U = 30.0 cm. The readings and results are shown in Table 3.1. hI Another student suggests that the magnification m is equal to the ratio . hO (i) State whether the results agree with the suggestion. Justify your statement by reference to the results. statement .......................................................................................................................... justification ........................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... [2] (ii) Suggest how you would continue to use the same apparatus to test the suggestion that hI the magnification m is equal to the ratio . hO ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] [Total: 11]

Mark scheme: 3(a) hO = 1.5 or 15 1 unit to match result, cm or mm 1 3(b)(i) 2.0 cm 1 3(b)(ii) V = 80(.0) cm 1 Working from candidate’s v value shown 1 3(b)(iii) m correct calculation 1 3(b)(iv) hI / hO correct and to 2 significant figures 1 3(c)(i) Statement matches results (expect YES) 1 Justification matches statement and includes idea of within (or beyond) the limits of experimental accuracy 1 3(c)(ii) Change value of u / distance from object to lens 1 Take at least 5 sets of readings in total (or take at least 3 additional sets of readings) 1

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4 A student investigates the time taken for water to evaporate to dryness when heated from above. Fig. 4.1 shows the set-up. The power of the heater is constant. The following is also available: • supply of water at room temperature • metre ruler. infrared heater lead to power supply shallow dish water Fig. 4.1 Plan an experiment to investigate how one factor affects the time taken for the water to evaporate. You do not need to write about safety precautions. You should: • state any additional apparatus required • explain briefly how you would do the investigation • state the key variables that you would keep constant • 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 how you would use your readings to reach a conclusion. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 MP1 (stop)watch / clock / timer / chronometer 1 MP2 Measure / record time for evaporation / for water to disappear / for dish to become dry. 1 MP3 Repeat with a different volume / depth of water 1 OR different distance of heater from water / different height of heater MP4 One from: 1 Volume / depth of water (if not chosen variable) OR Height / distance of heater from water (if not chosen variable) MP5 One from: 1 Room temperature / (initial) water temperature Reference to avoiding draughts owtte Surface area of water Second variable from MP4 if wrong investigation MP6 Table with clear columns for time and chosen variable with appropriate units. These must be headed with both a 1 quantity (or a recognised symbol for it) and unit. MP7 Plot graph of chosen variable against time 1 OR an answer which suggests comparing values of chosen variable and time in table Additional graph notes: NOTE: – The principle to apply here is ‘could I draw a significantly better line, using these points, under examination conditions?’ If the answer is definitely ‘yes’, do not award the mark. NOTE: – If candidate’s scale consists of actual readings at equal intervals this will produce a perfect straight line! The only marks available in this case are the first (axes right way round and labelled) So maximum 1. If axes are wrong way round, the other 3 marks are still available.

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