Cambridge IGCSE Physics 0625 — 2010 Oct/Nov Paper 5 · Variant 3

1 In this experiment, you are to determine the density of the material of a metre rule. For Examiner’s Carry out the following instructions referring to Fig. 1.1. Use 50.0 cm mark a metre rule b mass X pivot Fig. 1.1 You are provided with a 100 g mass, labelled X. (a) Place the mass X on the rule and adjust its position so that the rule is as near as possible to being balanced with the 50.0 cm mark to the left of the pivot as shown in Fig.1.1. (i) Measure the distance a from the centre of the mass X to the pivot. a = ................................................. cm (ii) Measure the distance b from the pivot to the 50.0 cm mark on the rule. b = ................................................. cm (iii) Calculate the mass m of the metre rule using the equation k a m = where k = 100 g. b m = ...................................................... [3] (b) (i) Take measurements to determine the average width w of the metre rule. w = ................................................. cm (ii) Take measurements to determine the average thickness t of the metre rule. t = ................................................. cm (iii) Calculate the volume V of the metre rule using the equation V = lwt where l is the For length of the metre rule (100.0 cm). Examiner’s Use V = ...................................................... m (iv) Calculate the density ρ of the metre rule using the equation ρ = . V ρ = ...................................................... [6] (c) State the assumption that you have made about the position of the centre of mass of the metre rule. .......................................................................................................................................... ......................................................................................................................................[1] [Total: 10]

Mark scheme: 1 (a) a and b present and in cm [1] a + b < 50 cm [1] m correct calculation [1] (b) At least two values given for w or t [1] More than two values given for w and t [1] Sensible values for w and t [1] V calculation correct method [1] Density to 2 or 3 significant figures and unit [1] Value 0.5–1.5 [1] (c) Centre of mass at 50 cm mark/midpoint/middle (wtte) [1] [Total: 10]

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2 In this experiment you will investigate the rate of cooling of water under different conditions. For Examiner’s Carry out the following instructions referring to Fig. 2.1. You are provided with a supply of hot Use water. thermometer lid beaker A hot water Fig. 2.1 (a) Record the room temperature θr . θr = ................................................. [1] (b) (i) Pour approximately 75 cm3 of hot water into the beaker labelled A. Place the lid on the beaker and place the thermometer through the hole in the lid and into the water as shown in Fig. 2.1. (ii) When the temperature shown on the thermometer stops rising record in Table 2.1 the temperature θ at time t = 0 s and immediately start the stopclock. (iii) Record in the table the temperature of the water at 30 s intervals from t = 30 s until you have a total of seven values up to time t = 180 s. [2] (c) (i) Empty the water from beaker A. Place beaker A into the larger beaker labelled B. For Examiner’s (ii) Repeat the steps (b)(i), (ii) and (iii), recording the readings in Table 2.2. [2] Use Table 2.1 Table 2.2 t / θ/ t / θ/ (d) Complete the column headings in both tables. [1] (e) State whether the rate of cooling of the water is significantly faster or slower or about the same under the conditions used in part (c) (Table 2.2) compared with the conditions in part (b) (Table 2.1). Justify your answer by reference to your readings. statement ......................................................................................................................... justification ....................................................................................................................... ......................................................................................................................................[2] (f) If this experiment were to be repeated in order to check the results it would be important to control the conditions. Suggest two such conditions that should be controlled. 1. ...................................................................................................................................... .......................................................................................................................................... 2. ...................................................................................................................................... ......................................................................................................................................[2] [Total: 10]

Mark scheme: 2 (a) θr sensible value [1] (b)–(d) t in s, θ in °C [1] Correct t values [1] Table 2.1 temperatures decreasing [1] Table 2.2 temperatures decreasing [1] Evidence of temperatures to 1°C [1] (e) Statement matches readings [1] Justified by reference to readings Comparison given of changes in temperature with numbers [1] (f) Any two from: Same (starting) temperature (wtte) Constant room temperature/draughts (wtte)/environment/place Carry out in same time intervals/duration Same thermometer (wtte) NOT volume of water/location of thermometer/beaker/‘temperature’ alone If > 2 responses, –1 for each additional incorrect (ignore ‘neutrals’) [2] [Total: 10] IGCSE – October/November 2010 0625 53

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3 In this experiment, you will investigate the potential difference across a resistor. For Examiner’s Carry out the following instructions referring to Fig. 3.1. Use power supply X A B V Fig. 3.1 The circuit provided contains a resistor X. There is a gap in the circuit between points A and B to be used for adding extra resistors, of resistance R, to the circuit. (a) Connect points A and B together. Switch on. Measure the potential difference V0 across resistor X. V0 = ..................................................[1] Switch off and separate points A and B. (b) (i) Do not change the position of the voltmeter in the circuit. Connect the 3.3 Ω resistor between points A and B. Switch on and record in Table 3.1 the potential difference V across the resistor X. Switch off and disconnect the 3.3 Ω resistor from between A and B. (ii) Repeat the steps in part (b)(i) with each of the other two extra resistors. (iii) Repeat the steps in part (b)(i) with the 3.3 Ω and 6.8 Ω resistors connected in series with each other. (iv) Complete the column headings in the table. Table 3.1 R / V / 3.3 4.7 6.8 10.1 [3] (c) Plot the graph of V / V (y-axis) against R / Ω (x-axis). Begin both axes at 0. For Examiner’s Use [4] (d) Use the graph to estimate the value of potential difference V when R = 0 Ω. Show clearly on the graph how you obtained your result. V = ..................................................[2] [Total: 10]

Mark scheme: 3 (a) V0 sensible value 1.0–2.5 [1] (b) Table: R in Ω, V in V [1] All V to at least 1 d.p. [1] V values decreasing [1] (c) Graph: axes labelled and scales suitable (origin included) [1] All plots correct to nearest ½ small square [1] Well judged best fit line [1] Thin line [1] (d) Line extended suitably to y axis [1] Estimate correct to ½ small square [1] [Total: 10]

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4 In this experiment you will investigate shadows formed on a screen. For Examiner’s Carry out the following instructions referring to Fig. 4.1. Use light screen source x object card A support 30.0 cm Fig. 4.1 You are provided with a lamp behind a piece of card. The card has a circular hole which in this experiment is referred to as the light source. (a) Place the screen so that its centre is 30.0 cm from the light source. (b) Measure the diameter d of the circular object card labelled A. d = ............................................ cm [1] (c) Place the object card A at a distance x = 2.0 cm from the screen. Switch on the light source. Measure and record in Table 4.1 the diameter s of the shadow of the object card formed on the screen. The screen has a sheet of graph paper taped to it. You may mark the graph paper to assist in measuring the diameter of the shadow. (d) Repeat the steps in (c) using values of x = 4.0 cm, 6.0 cm, 8.0 cm and 10.0 cm. Table 4.1 x /cm s /cm s 2/cm2 [5] (e) Calculate the values of s 2 and enter them in the table. [1] (f) A student suggests that the value of s 2 when x = 10.0 cm should be twice the value of For s 2 when x = 2.0 cm. State whether your experimental results support this suggestion Examiner’s and justify your statement by reference to your results. Use statement ......................................................................................................................... explanation ...................................................................................................................... ......................................................................................................................................[2] (g) State one precaution you took in order to obtain reliable measurements. .......................................................................................................................................... ......................................................................................................................................[1] [Total: 10]

Mark scheme: 4 (b) d = 2.8–3.2 cm [1] (c)–(e) correct × values 2.0, 4.0, 6.0, 8.0, 10.0 [1] s values present and increasing [1] s2 values correct [1] s2 values all to same number of significant figures (2, 3 or 4) [1] All above in correct units [1] Final s2 value 2× first value (± 10%) [1] (f) Correct statement matching results [1] (g) Justified referring to specified results (either exact or within limits of experimental accuracy, or wtte) [1] (h) Any one of: Use of darkened room How to avoid parallax when taking readings Use of marks paper on screen to aid measurements Card and screen vertical Repeats [1] [Total: 10]

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