NYJC 2024 H2 PHY 9749 P4 Answers

NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS TUTOR’S NAME CENTRE NUMBER S INDEX NUMBER PHYSICS 9749/04 Paper 4 Practical 19 August 2024 2 hours 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your name, class, tutor’s name, Centre number and index number in the spaces at the top of this page. Write in dark blue or black pen on both sides of the paper. You may use a HB 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 on the practical shift and laboratory, where appropriate, in the boxes provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. Shift Laboratory For Examiner’s Use 1 2 3 4 Total / 55 This document consists of 18 printed pages. H

2 NYJC 2024 9749/04/PRELIM 1 In this experiment, you will investigate the resistivity of a constantan wire. (a) (i) Connect the circuit as shown in Fig. 1.1 with the switch open. The wire on rule B should be connected by a crocodile clip at each end. L is the length of wire between the crocodile clips. (ii) With the switch open, record the voltmeter reading V. V = [2] (b) (i) Measure and record the length L. L = . (ii) Estimate the percentage uncertainty in your value of L. Fig. 1.1 1.583 V 1.4 V- 1.6V Correct range, units and dp 1.02m – 1.07m Correct range, units and dp [1]. Either one wrong is 0m 1.050 m L = 0.2 – 0.5 cm Percentage uncertainty = 𝛥𝐿 𝐿 × 100% = 0.3 105 × 100% = 0.3% 1 or 2 sf [1]. jockey Examiners’ comments: Students must measure the length carefully. The correct range needs to be given.

3 NYJC 2024 9749/04/PRELIM [Turn over percentage uncertainty = . [1] (c) (i) Close the switch. Place jockey on the wire on rule A at a distance x from the end of the rule, as shown in Fig. 1.2. The value of x should be about 40 cm. (ii) Measure and record the distance x and the ammeter reading I. x = . I = . (iii) Remove the jockey from the wire on rule A and open the switch. (d) Repeat (c) for further values of x and the corresponding values of I. [3] Fig. 1.2 0.3 % 40.0 cm 0.33 A x/ cm I / A 1 x / cm -1 20.0 0.51 0.0500 30.0 0.40 0.0333 40.0 0.33 0.0250 50.0 0.30 0.0200 60.0 0.23 0.0167 70.0 0.21 0.0143 80.0 0.19 0.0125 6 or more sets of data collected without assistance/ intervention [1] Each column heading x, I and 1/x, is a quantity and has a unit [1] All values of x and I to the correct values, d.p. AND correct s.f. for 1/x [1] jockey Examiners’ comments: Many are able to calculate the percentage error. Common error is the wrong choice of L. Examiners’ comments: Some readings of I are not possible, which shows that the experiment was set up wrongly. Many did not maximise the range of the wire. Most are able to write the table correctly.

4 NYJC 2024 9749/04/PRELIM (e) Theory suggests that I and x are related by the expression I P Qx=+ where P and Q are constants. Plot a suitable graph to determine the values of P and Q. A graph of I is plotted against 1/ x, with gradient equals to P and y-intercept equals to Q. gradient = 0.5000−0.1950 0.0470−0.0100 = 8.24 A cm 𝑃 = 8.24 A cm y-intercept = 0.500 – 8.24 (0.0470) = 0.113 A Q = 0.113 A y-intercept correctly read off to the nearest half small square OR correctly determined from y = mx + c using a point on the line [1] Distance between points chosen for gradient calculation > half length of drawn line AND gradient read-offs accurate to half a small square AND gradient calculated correctly [1] Values of P and Q calculated correctly with units [1] P = . Q = . [3] (f) The experiment is repeated with a battery of larger value of e.m.f. Sketch a line on your graph grid used in (e) to show the expected result. Label this line W. [1] [ Total: 12] Larger y-int [B1] Ignore the gradient (which should be the same). Examiners’ comments: • Sf and dp rules should always be applied in calculations. • The number of dps of readings off a 5-scale should reflect the uncertainty of ½ of the smallest square For example: 1 division : 5 → uncertainty = ½  (5 / 10 squares) = 0.3 (1 sf)

5 NYJC 2024 9749/04/PRELIM [Turn over [3]      / A / cm−1 Sensible scales AND plotted points occupy at least half the graph grid in both directions AND axes labelled [1] All observations must be plotted to an accuracy of half a small square [1] Best-fit line drawn [1] (0.0100, 0.1950) (0.0470,0.5000 ) Examiners’ comments: • Candidates who chose scales 1 division: 2.5 or 4 often (almost 50%) make errors in plotting and/or reading. It is strongly recommended that candidates use only scales 1 division: 1, 2 or 5.   0 0.60

6 NYJC 2024 9749/04/PRELIM 2 In this experiment, you will investigate the oscillations of a torsional pendulum. Set up the provided apparatus as shown in Fig 2.1. Adjust the lengths of the strings such that the red markings on the strings lie just below the disc B, and secure the strings to disc B using the binder clips provided. Place four 50g masses on the centre of disc A in a vertical stack Fig 2.1 (Front view) (a) Measure and record the distance L between the two discs. L = cm [1] (b) Displace disc A by a small angle about the centre of the disc. Release the disc so that it performs torsional oscillations in the horizontal plane about its centre. (See Fig. 2.2.) Fig. 2.2 (Top view) clips disc B retort stand L disc A stacked masses red marking 50.5 1 dp of cm, 49 cm < L < 52 cm B1 oscillations of disc A small angular displacement masses Examiners’ comments: Some readings of L are not possible, which shows that the experiment was set up wrongly.

7 NYJC 2024 9749/04/PRELIM [Turn over Make measurements to determine the frequency f of the oscillations f = Hz [3] (c) Make further measurements to determine the mass M required at the centre of disc A such that the frequency f of the oscillations is 1.50 Hz. Show your working clearly. M = g [3] (d) (i) Explain why it is not