Cambridge IGCSE Physics 0625 — 2015 May/June Paper 6 · Variant 2

1 The class is investigating a pendulum. Figs. 1.1 and 1.2 show the pendulum. clamp clamp l bob one complete oscillation Fig. 1.1 Fig. 1.2 (a) A student adjusts the pendulum until its length l = 50.0 cm. State one precaution that you would take to measure the length l as accurately as possible. You may draw a diagram. ................................................................................................................................................... ...............................................................................................................................................[1] (b) The student displaces the pendulum bob slightly and releases it so that it swings. She measures the time t for 20 complete oscillations of the pendulum (see Fig. 1.2). (i) Record the time t, in s, shown on the stopwatch in Fig. 1.3. 0 : 28 40 Fig. 1.3 t = ....................................................... s [1] (ii) Calculate the period T of the pendulum. The period is the time for one complete oscillation. T = ...........................................................[1] (iii) Explain why measuring the time for 20 oscillations, rather than 1 oscillation, gives a more accurate value for T. ........................................................................................................................................... .......................................................................................................................................[1] (c) The student adjusts the length of the pendulum until its length l = 100.0 cm. She repeats the procedure and obtains a value for the period T. T = ...............................................................2.06 s Another student suggests that doubling the length l of the pendulum should double the period T. State whether the results support this suggestion. Justify your answer by reference to the results. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... [2] (d) To continue the investigation of the relationship between the length l of the pendulum and the period T, it is necessary to use a range of values of length l. List additional l values that you would plan to use in the laboratory. ...............................................................................................................................................[2] [Total: 8]

Mark scheme: 1 (a) any one from: • reference to how to determine the centre of the bob • measure to top of bob then add on half diameter measured with blocks and rule or callipers • measure to top and bottom of bob and average • reference to perpendicular viewing (reducing parallax) • rule parallel with/close to string/appropriate use of set-square [1] (b) (i) t = 28.4(0) NOT 28:4 [1] (ii) T = 1.42 (s) allow ecf from (i) [1] (iii) reduce effect of errors in starting/stopping stopwatch [1] (c) statement to match results (expect no) [1] justification using results, including idea of difference is beyond limits of experimental uncertainty owtte [1] (d) minimum of three more values [1] all values ≥ 20 cm and ≤ 300 cm, and three values are at least 10 cm apart [1] [Total: 8] o

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2 The class is investigating the cooling of water. (a) A student pours 100 cm3 of hot water into a beaker. He places a thermometer in the water. Fig. 2.1 shows the thermometer. °C 110 100 90 80 70 60 50 40 30 20 water 10 0 –10 Fig. 2.1 (i) Record the temperature θH of the hot water as shown on the thermometer in Fig. 2.1. θH = ...........................................................[1] (ii) State one precaution that you would take to ensure that the temperature reading for the hot water is as reliable as possible. ........................................................................................................................................... .......................................................................................................................................[1] (b) The student adds 50 cm3 of cold water to the hot water. He records the temperature θ1. = ...............................................................71 °C θ1 Calculate the decrease in temperature θA using the equation θA = (θH – θ1). θA = ...........................................................[1] (c) The student adds a further 100 cm3 of cold water to the water in the beaker. He records the temperature θ2. = ...............................................................57 °C θ2 Calculate the decrease in temperature θB using the equation θB = (θ1 – θ2). θB = ...........................................................[1] (d) Suggest two factors, other than the volume and temperature of the cold water added, that affect the decrease in temperature of the hot water. 1. ............................................................................................................................................... ................................................................................................................................................... 2. ............................................................................................................................................... ................................................................................................................................................... [2] (e) Describe briefly how a measuring cylinder is read to obtain an accurate value for the volume of water. You may draw a diagram. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[2] [Total: 8]

Mark scheme: 2 (a) (i) θH = 92 (oC) [1] (ii) any one from: • wait for thermometer reading to stop rising • perpendicular viewing of scale • stirring • thermometer bulb in middle of water/not touching beaker [1] (b) θA = 21 (°C) allow ecf from (i) [1] (c) θB = 14, correct unit seen, °C or deg C NOT C° or °C, and not contradicted [1] (d) any two from: • room temperature/other environmental statement • initial hot water temperature • heat loss to surroundings /evaporation/conduction through sides of beaker • time delays in adding water [max.2] (e) perpendicular viewing/eye level with meniscus [1] reading to bottom of meniscus [1] [Total: 8]

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3 The class is investigating the resistance of lamps. Fig. 3.1 shows the first circuit used. power supply A V Fig. 3.1 (a) A student measures the potential difference VP across the lamps and the current IP in the circuit. The readings are shown in Figs. 3.2 and 3.3. 4 5 6 3 7 0.4 0.6 2 8 0.2 0.8 1 9 0 10 0 1.0 V A Fig. 3.2 Fig. 3.3 (i) Write down the readings shown on the meters. VP = ............................................................... IP = ............................................................... [2] VP (ii) Calculate the resistance RP of the lamp filaments using the equation RP = . IP RP = ...........................................................[1] (b) The student rearranges the circuit so that • the lamps are in series • the ammeter will measure the total current in the circuit • the voltmeter will measure the potential difference across all three lamps. In the space below, draw a diagram of this circuit using standard circuit symbols. [2] (c) The student measures the potential difference VS across the lamps and the current IS in the circuit in (b). VS = ...............................................................2.5 V IS = ...............................................................0.22 A VS Calculate the resistance RS of the lamp filaments using the equation RS = . IS RS = ...........................................................[1] (d) (i) A student wishes to vary the current in the first circuit, shown in Fig. 3.1, using a variable resistor. In the space below, draw the standard circuit symbol for a variable resistor. [1] (ii) On Fig. 3.1, label with X a suitable position in the first circuit for a variable resistor used to vary the current in all the lamps. [1] [Total: 8]

Mark scheme: 3 (a) (i) V = 2.4(0) (V) [1] I = 0.84 (A), both units correct [1] (ii) RP = 2.86 OR 2.9 (Ω) ecf (a)(i) [1] (b) lamps in series [1] voltmeter and ammeter in correct position, with rest of circuit and symbols correct [1] (c) RS = 11.4 OR 11 (Ω) NOT more than 3 sig. figs. [1] (d) (i) correct symbol for variable resistor NOT potentiometer [1] (ii) X correctly positioned [1] [Total: 8]

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4 The class is investigating reflection using a plane mirror. Fig. 4.1 shows a student’s ray-trace sheet. The student uses an A4 sheet of plain paper. A e M R 30° B ray-trace sheet eye Fig. 4.1 (a) On Fig. 4.1, the mirror is placed along the line MR. Label the normal NL. [1] (b) The student places two pins P1 and P2 on line AB at a suitable distance apart, so that she can accurately observe the reflection of line AB. Suggest a suitable distance between the two pins. distance = ...........................................................[1] (c) The student determines the angle between the reflected ray and the normal by viewing the images of pins P1 and P2 from the direction indicated by the eye in Fig. 4.1. She places two pins P3 and P4, some distance apart, so that pins P3 and P4, and the images of P2 and P1, all appear exactly one behind the other. She draws a line joining the positions of P3 and P4. She measures the angle α between the normal and the line joining the positions of P3 and P4. At this stage the angle θ between the mirror and line MR is 0 °, as shown in Table 4.1. She moves the mirror to a new position, shown by the dotted line on Fig. 4.1, at an angle θ = 10 ° to MR. She repeats the procedure with pins P3 and P4. She continues using angles θ = 20 °, 30 ° and 40 °. The readings are shown in Table 4.1. Table 4.1 θ/ ° α/ ° 0 32 10 50 20 69 30 92 40 108 (i) Plot a graph of α/ ° (y-axis) against θ/ ° (x-axis). [5] (ii) State whether your graph line shows that the angle α is directly proportional to the angle θ. Justify your statement by reference to your graph line. statement .......................................................................................................................... justification ........................................................................................................................ ........................................................................................................................................... [2] (iii) Suggest why, when this experiment is carried out carefully, the points plotted may not all lie on the graph line. ........................................................................................................................................... .......................................................................................................................................[1] [Total: 10]

Mark scheme: 4 (a) normal labelled NL [1] (b) P1P2 distance > 5 cm, < 30 cm [1] (c) (i) Graph: • axes correctly labelled [1] • suitable scales [1] • all plots correct to ½ small square [1] • good line judgement [1] • thin, continuous line [1] (ii) no [1] line does not pass through origin [1] (iii) difficulty in aligning pins OR pins too thick OR thickness of mirror [1] [Total: 10]

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5 The class is investigating the image formed by a converging lens. Fig. 5.1 shows the experimental set up. illuminated object u v screen lens Fig. 5.1 A student positions the illuminated object and the lens and then moves the screen away from the lens until a sharply focused image of the object is formed on the screen. The student measures the distances u and v, as shown in Fig. 5.1. u = ...............................................................25.8 cm v = ...............................................................36.2 cm uv (a) Calculate the focal length f of the lens using the equation f = Give your answer to a (u + v). suitable number of significant figures for this experiment. f = ...........................................................[2] (b) State two precautions you would take in the laboratory in order to obtain reliable measurements when doing this experiment. 1. ............................................................................................................................................... 2. ............................................................................................................................................... [2] Question 5 continues on the next page. (c) The object in Fig. 5.1 is an illuminated triangle, as shown in Fig. 5.2. Fig. 5.2 Suggest two differences between the appearance of the illuminated object and the well- focused image on the screen. 1. ............................................................................................................................................... 2. ............................................................................................................................................... [2] [Total: 6]

Mark scheme: 5 (a) f = 15.06(387) [1] final answer given to 2 or 3 significant figures AND unit [1] (b) any two from: • darkened room / bright(er) lamp / no other lights • moving screen slowly / back and forth to obtain best image • mark block to show centre of lens • place rule on bench/ clamp rule; • lens and object same (vertical) height/level (from bench) • lens, object and screen vertical/perpendicular to bench; • repeat measurement/experiment (and average) [max.2] (c) any two from: • upside down/inverted • size/bigger • brightness/brighter/dimmer • colours seen round edge/edges blurred [max.2] [Total: 6]

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