Cambridge IGCSE Physics 0625 — 2022 May/June Paper 6 · Variant 2

1 A student investigates the balancing of a metre rule. Fig. 1.1 shows the apparatus. 50.0 cm mark metre rule P Q a b 0 100 10.0 cm mark pivot bench Fig. 1.1 (a) The student places the metre rule on the pivot at the 50.0 cm mark. She places object P with its centre on the metre rule at the 10.0 cm mark. The object covers the scale markings on the metre rule, as shown in Fig. 1.2. 0 20 30 40 50 60 70 80 90 100 Fig. 1.2 Explain briefly how to place object P as accurately as possible with its centre at the 10.0 cm mark. You may add to Fig. 1.2, or draw another diagram, to help your explanation. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] (b) The student places object Q on the metre rule and adjusts its position until the metre rule is as close to balancing as possible. She records the distance a = 40.0 cm between the centre of object P and the pivot. The centre of object Q is at the 71.2 cm mark. Determine, and record in Table 1.1, the distance b between the centre of object Q and the pivot. Show your working. [2] (c) She repeats the procedure with object P placed at the 15.0 cm mark, 20.0 cm mark, 25.0 cm mark and 30.0 cm mark. All the values of a and b are shown in Table 1.1. Table 1.1 a / cm b / cm 40.0 35.0 17.8 30.0 15.1 25.0 12.3 20.0 9.7 Plot a graph of a / cm (y-axis) against b / cm (x-axis). You do not need to start your graph from the origin (0,0). [4] (d) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = ......................................................... [2] (e) The gradient G of the graph is equal to the ratio of the masses of P and Q. Record the ratio R of the masses of P and Q. Give your answer to a suitable number of significant figures for this experiment. R = ......................................................... [2] [Total: 11]

Mark scheme: 1(a) explanation or diagram showing: equal readings either side of the 10 cm mark OR average of readings either side of the mark = 10 1 1(b) 71.2 – 50(.0) 1 21.2 1 1(c) axes correctly labelled with quantity AND unit AND the right way round 1 suitable scales (filling ⩾ ½ the grid) 1 five plots correct to ½ small square 1 good line judgement, thin, continuous line 1 1(d) triangle method clearly shown on graph, covering at least ½ of candidate’s line between extreme plots 1 G = 1.6–1.9 inclusive 1 1(e) R = G 1 R given to 2 or 3 significant figures 1

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2 A student investigates the resistances of combinations of resistors. The first circuit arrangement is shown in Fig. 2.1. A RA RB V Fig. 2.1 (a) The student measures the current and decides to use a lower current. He adds a variable resistor to the circuit to reduce the current. On Fig. 2.1, mark with an X a suitable position in the circuit for the variable resistor. [1] 0.4 0.6 4 5 6 3 7 0.2 0.8 2 8 1 9 0 1.0 0 10 A V Fig. 2.2 Fig. 2.3 (b) (i) The student measures the current I1 in the circuit. Record the current shown in Fig. 2.2. I1 = .......................................................A [1] (ii) He measures the potential difference (p.d.) V1 across resistors RA and RB in series. Record the potential difference V1 shown in Fig. 2.3. V1 = .......................................................V [1] (c) Calculate the resistance R1 of the combination of resistors in series. Use the equation V1 R1 = I . 1 Include the unit. R1 = ......................................................... [1] (d) The student connects a resistor RC in parallel with resistors RA and RB. He does not change the series combination of resistors RA and RB. He connects the voltmeter across the combination of all three resistors. (i) Draw a circuit diagram showing the circuit described in (d). [2] (ii) The student measures the current I2 in the circuit. 0.68 I2 = ............................................................ A He measures the potential difference V2 across the combination of the three resistors. 2.1 V2 = ............................................................ V Calculate the resistance R2 of the combination of resistors. Use the equation V2 R2 = . I2 Include the unit. R2 = ......................................................... [1] (e) The student rearranges the resistors to set up the circuit shown in Fig. 2.4. A RA RB RC V Fig. 2.4 He measures the current I3 in the circuit. I3 = ............................................................0.29 A He measures the potential difference V3 across the combination of the three resistors. 2.1 V3 = ........................................................... V Calculate the resistance R3 of the combination of resistors. Use the equation V3 R3 = . I3 Include the unit. Give your answer to a suitable number of significant figures for this experiment. R3 = ......................................................... [1] (f) A student thinks the three resistors RA, RB and RC have the same resistance within the limits of experimental accuracy. (i) Suggest how the student could use the apparatus provided to test his idea. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (ii) Explain how the student can decide whether the values of resistance are the same within the limits of experimental accuracy. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1]

Mark scheme: 2(a) X marked anywhere in the series circuit 1 2(b)(i) I1 = 0.24 (A) 1 2(b)(ii) V1 = 2.2(0) (V) 1 2(c) R1 = 9.17 / 9.2 () 1 Question Answer Marks 2(d)(i) RC in parallel with resistors in series 1 voltmeter across candidate’s combination AND the rest of the circuit correct 1 2(d)(ii) 3.09 with unit  seen at least once in (c) (d) or (e) and not contradicted 1 2(e) R3 = 7.24 () to 2 or 3 significant figures 1 2(f)(i) use of a voltmeter and/or an ammeter 1 measure V and I for each resistor and calculate R OR connect each resistor to the same voltage supply and measure the current OR connect resistors in series and measure the voltage across each of them OR connect resistors in parallel and measure the current through them 1 2(f)(ii) check to see if the results are equal / close / within 10% 1

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3 A student determines the focal length f of a lens. Fig. 3.1 shows the set-up. illuminated object x y z screen lens bench Fig. 3.1 (a) (i) On Fig. 3.1, measure the distance x from the screen to the illuminated object. x = ............................................................... Fig. 3.1 is drawn to scale. The actual distance D between the illuminated object and the screen is 75.0 cm. She places the lens between the object and the screen so that the lens is close to the illuminated object. She moves the lens away from the object until a clearly focused image is formed on the screen. On Fig. 3.1, measure the distance y between the centre of the lens and the illuminated object. y = ............................................................... On Fig. 3.1, measure the distance z between the centre of the lens and the screen. z = ............................................................... [2] Table 3.1 D / cm u / cm v / cm f / cm 75.0 85.0 19.1 64.1 14.4 (ii) Calculate, and record in Table 3.1, the actual distance u between the centre of the lens and the illuminated object. Calculate, and record in Table 3.1, the actual distance v between the centre of the lens and the screen. [1] (iii) Calculate, and record in Table 3.1, the focal length f of the lens using the equation uv f = . D [1] (b) The student places the screen at a distance D = 85.0 cm from the illuminated object. She repeats the procedure described in (a). The results are shown in Table 3.1. Calculate the average value fA of the focal length of the lens. Show your working. fA = ................................................... cm [2] (c) State two precautions that you would take to obtain accurate readings in this experiment. 1. ............................................................................................................................................... ................................................................................................................................................... 2. ............................................................................................................................................... ................................................................................................................................................... [2] (d) A student states that a more accurate value for the focal length f of the lens can be determined by plotting a graph of uv against D. The gradient of the graph is numerically equal to the focal length. (i) Suggest a suitable number of sets of readings that the student should take. ..................................................................................................................................... [1] (ii) Explain briefly how this graphical method can give a more accurate value for the focal length. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... [2] [Total: 11]

Mark scheme: 3(a)(i) x = 7.5 cm, y = 2.0 cm and z = 5.5 cm 1 all to nearest millimetre 1 3(a)(ii) u = 20 and v = 55 1 3(a)(iii) f = 14.6(6666667) (cm) 1 3(b) working shown 1 fA calculation correct 1 Question Answer Marks 3(c) any two from: use darkened room / bright(er) object move lens slowly (to find sharpest image) move lens back and forth (to find sharpest image) ensure that object, lens and screen are vertical object and (centre of) lens same height (above bench) perpendicular reading/viewing of the ruler scale mark the centre of the lens on its holder 2 3(d)(i) any integer between 5 and 15 (inclusive) 1 3(d)(ii) (a straight line) is a way of taking an average 1 anomalous results can be seen (and repeated or ignored) 1

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4 A student investigates insulators. Plan an experiment to list insulating discs in order from best insulator to worst insulator. The following apparatus is available: • five discs made from different insulating materials • a thermometer • a stop-watch • a heated metal cylinder (see Fig. 4.1) • a second metal cylinder with a hole for the thermometer (see Fig. 4.1). heated metal cylinder insulating disc electrical heater metal cylinder thermometer Fig. 4.1 You can also use other apparatus and materials that are usually available in a school laboratory. In your plan, you should: • explain briefly how you would carry out the investigation • state the key variables that you would control • 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 method: MP1 place disc between heated cylinder and metal cylinder / set up apparatus as shown in diagram 1 MP2 measure the time for lower cylinder to reach a certain temperature (rise) / measure the temperature (rise) reached in a certain time. 1 MP3 repeat with the other discs 1 MP4, MP5 key variables: any two from: thickness of disc temperature of heated cylinder initial temperature of lower cylinder initial temperature of the disc voltage/current/power of heater time (of heating) (if temperature change is measured) OR temperature change (if time of heating is measured) 2 MP6 table: table with columns for (material of) disc, time / temperature difference (depending on MP2) with units in the headings only 1 MP7 conclusion: (draw a graph/bar chart to) compare temperatures reached (in a certain time) / heating times (for a given temperature rise) with the material of the insulator – the disc with the lowest (final) temperature (difference) / takes the longest time, is the best insulator 1 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 mark available in this case is 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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