CJC J2.H2.PRELIM.2024.P4 - Soln w ER

Catholic Junior College JC2 Preliminary Examinations Higher 2 CANDIDATE NAME MARK SCHEME CLASS 2T INDEX NUMBER PHYSICS 9749/04 Paper 4 Practical 19 August 2024 2 hour 30 minutes Candidates answer on the Question Paper READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use an HB or 2B pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, glue or correction fluid. Answer all questions. Write your answers in the spaces provided on the question paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. Give details of the practical shift and laboratory where appropriate in the boxes provided. At the end of the assessment, fasten all your work securely together. The number of marks is given in brackets [ ] at end of each question or part question. This document consists of 23 printed pages and 1 blank page. Shift Laboratory For Examiner’s Use 1 / 15 2 / 6 3 / 23 4 / 11 Total / 55

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3 [Turn Over 1. In this experiment, you will investigate the current in an electrical circuit. (a) You have been provided with two identical metre rules, A and B. Set up the circuit shown in Fig. 1.1. Fig. 1.1 F, G, H and J are crocodile clips of the connecting leads. (i) Place H approximately half-way along the wire on rule B. The distance between F and H is d, as shown in Fig. 1.1. Place J on the wire on rule A so that the distance between G and J is approximately 60 cm. The distance between G and J is c, as shown in Fig. 1.1. Record d and c. d = ……………………………………………. c = ……………………………………………. [1]  Correct value of d in the range 49.5 – 50.4 cm.  Correct value of c in the range 59.5 – 60.4 cm.  Correct precision (d.p.) and units: 1 d.p. in cm or 3 d.p. in m.  Repeated readings not required. Examiners’ Comments:  Majority of the candidates obtained full credit.  Candidates are reminded to pay attention to the appropriate d.p. and units. (ii) Calculate n, where c dn d  . 60.0 50.0 0.20050.0    c dn d n = ……………………………………………. 50.0 cm A d c rule B F H rule A G J wire tape 60.0 cm 0.200

4 (iii) Close the switch. Record the ammeter reading I. I = ……………………………………… … [1] Value of I in the range 75.0 – 175.0 mA with unit.  Correct value of I in range 75.0 – 175.0 mA.  Correct units of I.  Correct precision of I, 1 d.p. in mA or 4 d.p. in A.  Repeat readings not required (optional). Examiners’ Comments:  Majority of the candidates managed to quote the correct d.p. with the corresponding units.  Candidates are reminded not to round off the values shown on the multimeter.  Candidates that did not obtain full credit had readings that were off the acceptable range.  Candidates need to note that when dealing with electrical circuits , make sure that the connections between wires are not loose. When modifying any part of the experiment, make sure to open the switch first. (iv) Open the switch. (b) Vary c such that c is greater than d and repeat (a)(iii), keeping d constant throughout. Present your results clearly. d = 50.0 cm c / cm I / mA n     2 1   n n 55.0 151.3 0.100 1.91 60.0 144.2 0.200 1.83 70.0 137.8 0.400 1.71 80.0 132.0 0.600 1.63 90.0 127.5 0.800 1.56 95.0 125.5 0.900 1.53 [5] 1 mark – 6 sets of readings of c and I showing correct trend. 1 mark – Range maximised: includes a reading of c ≥ 95.0 cm and no values of c < d. – Award only 1 mark if table only has 5 sets of readings. 1 mark – Column headings with quantity and correct unit. 1 mark – All values of c must be given to the nearest mm (or 1 d.p. in cm or 3 d.p. in m). 1 mark – Correct calculation of all values of     2 1   n n . n and     2 1   n n recorded to least s.f. (3 s.f.) Repeat readings not required (optional). Examiners’ Comments:  Majority of the candidates did well for this section  Candidates are reminded to always try to maximise their variations (in this case, c). 144.2 mA

5 [Turn Over (c) It is suggested that I and n are related by the expression  2 ( 1)    nS TnI where S and T are constants. Plot a suitable graph to determine the values of S and T. Plot a graph of I against     2 1   n n , a straight line graph with gradient S and vertical intercept T should be obtained. 156.4 125.6gradient = 65.532 mA2.0 1.53S    = 65.5 mA (3 s.f.) T = vertical intercept = 156.4 – (65.532)(2.0) = 25.336 mA = 25.3 mA (3 s.f.) S = ……………………………………………. T = ……………………………………………. [7] 3 marks – Graph  Axes labelled with units and good scale (no awkward scale and graph at least half the graph grid both vertically and horizontally).  All points plotted and plotted accurately to half smallest division.  Best-fit straight line drawn (satisfies the ‘3-checks’). 1 mark – Gradient calculation  Correct gradient formula.  Used 2 coordinates far apart on the best-fit line (separated by at least half the length of the line drawn).  Read off coordinates accurately to half the smallest division. 1 mark – y-intercept calculation  Correct formula used. Used coordinates from the best-fit line and not table. OR, if graph plotted from x = 0, y-intercept read off graph accurately to ½ smallest division. 1 mark – Determination of S and T  Equate gradient to S.  Equate y-intercept to T. 1 mark – Final answer of S and T  Final values of S and T to 3 sig. fig.  Correct units of S and T: mA or A. Examiners’ Comments:  Majority of the candidates did well for this section.  Candidates are reminded to use appropriate scales.  Candidates are to note that we can only read off the y -intercept when the best fit line cuts at zero for the x-axis. Do not try to start at (0, xxx) to force to read off the y-intercept in expense of being unable to cover at least half the grid size for all points plotted.  Final answers for gradient and y-intercept to keep to 3 s.f. 65.5 mA 25.3 mA

6  Best practice for the calculation of y -intercept is when the gradient is obtained, use one of the gradient coordinates to substitute back into the equation.  Candidates are reminded to always pay attention to the units for both gradient and y-intercept.  Candidates are reminded to complete their best fit line and make sure that the gradient triangle covers more than half the length of the best fit line. Pick two coordinates that can be easily read off.

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8 1.5 1.6 1.7 1.8 1.9 2.0 156 124 148 140 132 I / mA (2.0, 156.4) (1.53,125.6) 160 W 128 136 144 152 2.1 2.2

9 [Turn Over (d) Theory suggests that S is inversely proportional to d and that T is independent of d. The experiment is repeated using the same equipment but a larger value of d. For this experiment, draw a second line on the graph to show the expected results. Label this line W. [1] [Total: 15] 1 mark – Correct line W with smaller gradient and vertical intercept same as the first line