Cambridge IGCSE Physics 0625 — 2014 May/June Paper 5 · Variant 2

1 In this experiment, you will take measurements of a pencil. Carry out the following instructions referring to Fig. 1.1. pencil sharpened section x y l Fig. 1.1 (a) (i) Measure, in cm, the total length l of the pencil supplied. l = ...............................................cm (ii) Measure, in cm, the length x of the unsharpened section of the pencil. x = ...............................................cm (iii) Calculate the length y of the sharpened section of the pencil, using the equation y = (l – x). y = ...............................................cm [2] (b) Use the string and the ruler to determine the circumference c of the unsharpened section of the pencil. Show your working. c = ..........................................cm [3] (c) Suggest a source of inaccuracy in determining the circumference of the pencil. ................................................................................................................................................... ...............................................................................................................................................[1] c2x (d) Calculate the volume V of the unsharpened section of the pencil using the equation V = . 4π V = ................................................[2] (e) Estimate the volume VE of the sharpened section of the pencil. Show your working or reasoning. VE = ................................................[2] [Total: 10]

Mark scheme: 1 (a) (i) (ii) l and x recorded in cm, with l between 15 and 18 cm and x between 13 and 17 cm [1] (iii) correct calculation of y [1] (b) evidence of at least three turns (accept from a sketch) [1] working / method shown [1] c between 2 and 3 cm and to nearest 0.1 cm [1] (c) any one from: • stretching of string • thickness of string • thickness of mark • gaps between turns • winding of turns at an angle [1] (d) correct calculation of V to 2 or 3 significant figures (penalise rounding errors) [1] cm3 [1] (e) suitable answer < 1 (cm3) (expect estimate to nearest 0.1 cm3) [1] sensible reasoning / working / method which takes account of sharpened shape and length [1] [Total: 10]

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2 In this experiment, you will investigate the cooling of water. Carry out the following instructions referring to Fig. 2.1. thermometer water Fig. 2.1 (a) Pour 200 cm3 of hot water into the beaker. Place the thermometer in the beaker of hot water, as shown in Fig. 2.1. (i) When the thermometer reading stops rising, record in Table 2.1 the temperature θH of the hot water at time t = 0 s. Immediately start the stopclock. (ii) After 30 s, measure the temperature θ shown on the thermometer. Record the time t = 30 s and the temperature reading in the table. (iii) Continue recording the time and temperature readings every 30 s until you have six sets of readings. Table 2.1 t /s θ/ °C 0 [2] (b) Plot a graph of θ / °C (y-axis) against t/ s (x-axis). [5] (c) (i) Describe briefly the shape of the best-fit graph line that you have drawn. ........................................................................................................................................... (ii) State what the shape of the graph line tells you about the change, if any, in the rate of cooling of the water during the experiment. ........................................................................................................................................... ........................................................................................................................................... [2] (d) Describe briefly how you would read a measuring cylinder to obtain an accurate value for the volume of water. You may draw a diagram. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[1] [Total: 10]

Mark scheme: 2 (a) correct t values 30, 60, 90, 120, 150 [1] temperatures decreasing (accept 1 pair of identical readings) [1] (b) axes correctly labelled with quantity and unit [1] suitable scales on both axes, occupying more than half the grid [1] all plots correct to ½ small square [1] good line judgement [1] thin, continuous line and neat plots (penalise large ‘blobs’) [1] (c) (i) statement to match results [1] (ii) statement to match graph line [1] IGCSE – May/June 2014 0625 52 (d) clear description or diagram to show one from: • perpendicular line of sight • reading to bottom of meniscus [1] [Total: 10]

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3 In this experiment, you will investigate the resistance of a resistor. Carry out the following instructions, referring to Fig. 3.1. power supply Y Z A X S resistor resistance wire V Fig. 3.1 (a) (i) Switch on. Connect the sliding contact S to point X in the circuit. Measure and record the potential difference V across the resistor and the current I in the circuit. Switch off. V = .................................................... I = .................................................... [2] V (ii) Calculate the resistance R of the resistor using the equation R = I. R = ................................................[1] (b) (i) Switch on. Connect the sliding contact S to point Y in the circuit. Measure and record the potential difference V across the resistor and the current I in the circuit. Switch off. V = .................................................... I = .................................................... [1] V (ii) Calculate the resistance R of the resistor using the equation R = I. R = .................................................... (c) (i) Switch on. Connect the sliding contact S to point Z in the circuit. Measure and record the potential difference V across the resistor and the current I in the circuit. Switch off. V = .................................................... I = .................................................... V (ii) Calculate the resistance R of the resistor using the equation R = I. R = .................................................... [2] (d) State how the value of R changes when I decreases. ................................................................................................................................................... ...............................................................................................................................................[1] (e) A student carries out this experiment using a different resistor. He takes readings using various lengths of resistance wire in the circuit. He plots a graph of V / V against I / A. Fig. 3.2 is a sketch of the graph. V / V 0 0 I / A Fig. 3.2 Explain briefly how the student would use the graph to determine the gradient of the line. You may draw on the graph of Fig. 3.2. You are not asked to calculate the value of the gradient. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[2] (f) In this experiment, the resistance wire XYZ acts as a variable resistor (rheostat). Draw the standard circuit symbol for a variable resistor. [1] [Total: 10]

Mark scheme: 3 (a) (i) V to at least 1 d.p. and < 3 V [1] I to at least 2 d.p. and < 1 A [1] (ii) R calculated correctly (penalise incorrect rounding) [1] (b) V and I recorded with I less than in (a) [1] (c) (i) V in V, I in A, R in Ω in (a), (b) or (c) at least once, not contradicted [1] (ii) R to 2 or 3 significant figures [1] (d) R constant (provided it matches results) no e.c.f. [1] (e) clear description or diagram showing triangle method with large triangle or taking two co-ordinates far apart on line [1] how to calculate gradient e.g. equation or rise / run, etc. [1] (f) standard symbol for variable resistor (rectangle with strike-through arrow) [1] [Total: 10]

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4 In this experiment, you will determine the focal length of a converging lens. Carry out the following instructions, referring to Fig. 4.1. D illuminated object x screen lens Fig 4.1 (a) Place the screen at a distance D = 80.0 cm from the illuminated object. The screen and the illuminated object must remain in the same positions throughout the experiment. (b) Place the lens close to the illuminated object. Move the lens until a sharply-focused, enlarged image of the object is seen on the screen. (i) Measure and record, in cm, the distance x from the illuminated object to the centre of the lens. x = ...............................................cm (ii) Measure and record, in cm, the height h from the top to the bottom of the image on the screen. h = ...............................................cm [2] (c) Move the lens towards the screen until a smaller, sharply-focused image of the object is seen on the screen. Measure and record, in cm, the distance y from the illuminated object to the centre of the lens. y = ..........................................cm [1] (d) (i) Calculate d using the equation d = (y – x). d = .................................................... (ii) Calculate d 2. d 2 = .................................................... [1] D2 – d 2 (e) Calculate the focal length f of the lens, using the equation f = . 4D f = ................................................[2] (f) State two precautions that you could take in this experiment to obtain reliable results. 1. ............................................................................................................................................... ................................................................................................................................................... 2. ............................................................................................................................................... ................................................................................................................................................... [2] (g) Sketch a diagram of the image seen in part (b). [1] (h) Suggest a variable that could be changed when repeating this experiment to check the accuracy of the value obtained for the focal length f. You are not asked to repeat the experiment. ...............................................................................................................................................[1] [Total: 10]

Mark scheme: 4 (b) x sensible value (20 ± 2) in cm [1] h sensible value (>1.5 cm) in cm [1] (c) y recorded and x + y in range 75.0 cm to 85.0 cm [1] (d) d and d 2 correct (penalise rounding errors for d 2) [1] (e) f to 2 or 3 significant figures and correct unit [1] f value 14 cm – 16 cm [1] IGCSE – May/June 2014 0625 52 (f) any two from: • use of darkened room / brighter lamp / no other lights • mark position of centre of lens on holder • place metre rule on bench / clamp in position • ensure object and (centre of) lens are same height (from the bench) • repeat (and average) • move the lens slowly / to and fro • lens, object and screen all vertical / perpendicular to bench [max 2] (g) image drawn inverted [1] (h) distance between object and screen / D / change position of screen [1] [Total: 10]

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