Cambridge IGCSE Physics 0625 — 2024 Feb/March Paper 6 · Variant 2

1 A student determines the mass of a metre ruler by a balancing method. He is using the apparatus shown in Fig. 1.1. a load b 50.0 cm mark 0.0 cm mark metre ruler bench pivot Fig. 1.1 (a) The student places a circular load on the metre ruler shown in Fig. 1.2. load metre ruler 25 26 27 28 29 30 31 Fig. 1.2 (not to scale) Determine the distance d of the centre of the load from the zero end of the ruler, as shown in Fig. 1.2. Fig. 1.2 is not to scale. d = ................................................... cm [1] (b) (i) The student adjusts the position of the metre ruler on the pivot until the metre ruler is as near as possible to being balanced. Describe a technique for ensuring that the ruler is as near as possible to being balanced. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (ii) The student finds that the ruler is as near as possible to being balanced when the pivot is at the 47.6 cm mark. Calculate the distance a of the centre of the load from the 50.0 cm mark, as shown in Fig. 1.1. Use your value of d from (a) and the equation a = (50.0 cm – d ). a = ......................................................... cm Calculate the distance b of the centre of the load from the pivot, as shown in Fig. 1.1. Use your value of d from (a) and the equation b = (position of pivot – d ). b = ......................................................... cm [2] (c) The student moves the load so that its centre is above the 5.0 cm mark and balances the metre ruler. He repeats this procedure for the load at the 10.0 cm mark, 15.0 cm mark, 20.0 cm mark and 25.0 cm mark. His results are shown in Table 1.1. Table 1.1 position of load / cm a / cm b / cm 5.0 45.0 40.5 10.0 40.0 35.2 15.0 35.0 31.5 20.0 30.0 26.0 25.0 25.0 22.5 (i) Plot a graph of a / cm, (y-axis) against b / cm, (x-axis). Use the values in Table 1.1. You do not need to start your axes at the origin (0,0). Draw the best-fit straight line. [4] (ii) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = ......................................................... [1] k (d) Calculate the mass M of the metre ruler using the equation M = , (G –1) where k = 25 g. Give an appropriate unit. M = ......................................................... [1] (e) The accuracy of the result obtained by this procedure depends on the metre ruler, without a load, balancing with the pivot at the 50.0 cm mark. A student finds that this does not happen. She adds a small piece of modelling clay to one end of the metre ruler to correct it. Suggest if this is a suitable change for this experiment. Explain your answer. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11]

Mark scheme: Question Answer Marks 1(a) d = 28(.0) (cm) 1 1(b)(i) balance point between where just tips one way then the other / words to that effect 1 1(b)(ii) a = 22(.0) and b = 19.6 1 both to nearest mm 1 1(c)(i) graph: 1 • axes labelled with quantity and unit • appropriate scales (plots occupying at least ½ grid) 1 • plots all correct to ½ small square and precise plots 1 • well-judged STRAIGHT line and thin line 1 1(c)(ii) G present and use of triangle method seen on graph 1 1(d) M in range 100 to 400 with unit of g 1 1(e) No, as (mass of clay) increases / changes mass of metre ruler 1 or Yes, as (mass of clay) only a small % of mass of metre ruler / owtte

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2 A student investigates a circuit containing different combinations of three resistors. She first uses Circuit A, shown in Fig. 2.1. Circuit A A P Q Fig. 2.1 (a) On Fig. 2.1, draw a voltmeter connected to measure the potential difference (p.d.) V for terminals P and Q. [1] (b) The student measures the potential difference V for terminals P and Q and measures the current I in the circuit. The meters are shown in Fig. 2.2 and Fig. 2.3. 2 3 0.4 0.6 1 4 0.2 0.8 0 5 0 1.0 V A Fig. 2.2 Fig. 2.3 Read and record, in the first line of Table 2.1, the values of V and I shown on the meters in Fig. 2.2 and Fig. 2.3. [2] Table 2.1 V / I / R / Circuit A Circuit B 2.9 0.22 Circuit C 2.6 0.86 (c) Circuit B The student connects the resistors between terminals P and Q as shown in Fig. 2.4. She measures and records, in Table 2.1, the values of V and I for this circuit. P Q Fig. 2.4 Circuit C The student connects the resistors between terminals P and Q as shown in Fig. 2.5. She measures and records, in Table 2.1, the values of V and I for this circuit. P Q Fig. 2.5 (i) Calculate and record in Table 2.1 a resistance R for each circuit. Use the values of V V and I from Table 2.1 and the equation R = . I [2] (ii) Add units to the column headings in Table 2.1. [1] (d) (i) Calculate a resistance RA. Use the value of R from Circuit A and the equation R RA = 3 RA = ............................................................... Calculate a resistance RB. Use the value of R from Circuit B and the equation R RB = 1.5 RB = ............................................................... Calculate a resistance RC. Use the value of R from Circuit C and the equation RC = 3R RC = ............................................................... [1] (ii) A student suggests that RA, RB and RC should all be equal. State whether your results support this suggestion. Justify your statement with reference to values from your results. statement .......................................................................................................................... justification ........................................................................................................................ ........................................................................................................................................... [2] (e) A student investigates the resistors in Circuit A using a variable resistor to change the current in the circuit. (i) In the space below, draw the symbol for a variable resistor. [1] (ii) Suggest one advantage of using a variable resistor to change the current in the circuit. ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 11]

Mark scheme: 2(a) correct voltmeter symbol in parallel with PQ 1 2(b) V = 3.1 1 I = 0.12 1 2(c)(i) R values correct (25.8 / ecf, 13.2, 3.02) 1 R values to consistent 2 or consistent 3 significant figures 1 2(c)(ii) units (V, A, ) 1 2(d)(i) values of RA, RB and RC ROUNDING to (8.6, 8.8, 9.1) 1 2(d)(ii) statement matching values of RA, RB and RC 1 justification referencing values and ‘limits of experimental accuracy’ 1 2(e)(i) correct circuit symbol for variable resistor 1 2(e)(ii) suitable advantage 1 e.g. easy to obtain range of values/ can easily set current to chosen values

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3 A student determines the focal length of a converging lens by two methods. illuminated object u v1 plain white screen lamp lens bench Fig. 3.1 (a) The student sets up the apparatus as shown in Fig. 3.1. Suggest one precaution that must be taken when setting up the apparatus to ensure accurate measurements. ................................................................................................................................................... ............................................................................................................................................. [1] (b) The student sets the distance u between the illuminated object and the lens to 20.0 cm. He places the screen near the lens and moves the screen until a sharp image of the illuminated object is seen on the screen. (i) Describe a technique for obtaining an image that is as sharp as possible. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Measure v1, the distance from the lens to the screen on Fig. 3.1. v1 = ........................................................ cm Fig. 3.1 is drawn to 1/10th scale. Calculate V1, the actual distance from the lens to the screen. V1 = ........................................................ cm [2] (c) The shapes of the illuminated object and the image seen on the screen are shown full size in Fig. 3.2 and Fig. 3.3. hI hhoo Fig. 3.2 Fig. 3.3 (i) Measure hO, the height of the illuminated object, as shown in Fig. 3.2. hO = ........................................................ cm Measure hI, the height of the image on the screen, as shown in Fig. 3.3. hI = ........................................................ cm [1] hI (ii) Calculate a value M for the magnification, using the equation M = . hO M = ......................................................... [1] (d) Calculate a value f1 for the focal length of the lens. Use your values from (b)(ii) and (c)(ii) and V1 the equation f1 = . (M + 1) f1 = ......................................................... [1] (e) Describe one difficulty that is experienced when using a ruler to measure the height of the image in this experiment. Suggest an improvement to the apparatus to overcome this. difficulty ..................................................................................................................................... ................................................................................................................................................... improvement ............................................................................................................................. ................................................................................................................................................... [2] (f) The student adjusts the position of the lens so that u = 40.0 cm and obtains a new value V2 for the distance between the lens and the screen. 25.1 V2 = ........................................................ cm Calculate a second value f2 for the focal length of the lens, using the equation uV2 f2 = (u + V2) . f2 = ......................................................... [1] (g) Suggest which value of focal length, f1 or f2, might be more accurate. Explain your answer. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11]

Mark scheme: 3(a) one precaution from: 1 (lamp), object and lens at same height / lens and screen perpendicular(to bench) / fix metre rule to bench 3(b)(i) move screen slowly / back and forth 1 3(b)(ii) v1 = 8(.0) (cm) 1 V1 = 80 / ecf (cm) 1 3(c)(i) hO = 1.2 (cm) and hI = 4.8 (cm) 1 3(c)(ii) correct calculation of M (4.0 / ecf) and no unit 1 3(d) f1 = 16(.0 cm) 1 3(e) any one valid difficulty (e.g. hand or ruler gets in way of light) 1 one improvement to overcome the difficulty (e.g. translucent screen (and measure from back) / fix grid to screen) 1 3(f) f2 = 15.4 and cm seen at least once in (d) or (f) and not contradicted 1 3(g) valid suggestion with reason 1 e.g: f2 as f1 has smaller measurements (i.e. ho and hi) (and so % uncertainties larger)

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4 A student investigates the effect of insulation on the cooling of a liquid. Plan an experiment which will enable her to investigate how changing the thickness of insulation surrounding a beaker affects the rate of cooling of hot water in the beaker. The apparatus available includes: • a glass beaker • a supply of hot water • a lid to fit the beaker • strips of insulation which can be cut to size. In your plan: • list any additional apparatus needed • explain briefly how to do the experiment, including the measurements to take so that the rate of cooling can be determined • state the key variables to keep 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. You may draw a diagram if it helps to explain your plan. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 MP1 apparatus: 1 thermometer and stopwatch MP2 method: 1 measure independent variable measure initial and final temperatures measure time MP3 repeat for new value of independent variable 1 MP4 control variable: 1 one (explicitly stated) from: volume of water, initial temperature MP5 table: 1 MUST be appropriate for method with: columns, with correct units, for independent and dependent variables any other quantity mentioned must have correct units MP6 analysis: 1 compare readings in the table to see if change in insulation thickness produces change in (rate of) temperature change (owtte), plot line graph (with axes specified) MP7 additional point (one from): 1 at least 5 sets of data taken, repeat for each value of independent variable and take average correct description of how to calculate rate of cooling from results

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