MI 2024 PU3 H2 PHYSICS PRELIM P3A QP

Class Adm No Candidate Name: This document consists of 17 printed pages and 1 blank page. [Turn over 2024 Preliminary Examination Pre-University 3 H2 PHYSICS 9749/03 Paper 3 Longer Structured Questions Section A Booklet 16 September Candidates answer on the Question Paper. 2 hours No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Do not turn over this page until you are told to do so. Write your full name, class and Adm 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 an HB pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, glue or correction fluid. The use of an approved scientific calculator is expected, where appropriate. Section A Answer all questions. Section B Answer one question only. You are advised to spend one and half hours on Section A and half an hour on Section B. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 / 10 2 / 10 3 / 10 4 / 11 5 / 9 6 / 10 Section B 7 / 20 8 / 20 Presentation (overall) P3 Total /80

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4 Section A Answer all the questions in the spaces provided. 1 (a) A bar magnet is suspended from a helical spring and one end of the magnet is situated in a coil of wire, as shown in Fig. 1.1. The coil is connected in series with a switch and a resistor. The switch is opened. Fig. 1.1 The bar magnet is displaced vertically and then released. As the magnet passes through its rest position, a timer is started. The variation with time t of the vertical displacement of the magnet from its rest position is shown in Fig. 1.2. At t = 4.0 s, the switch is closed. Fig. 1.2 (i) Use Fig. 1.2 to determine the frequency of oscillation of the magnet. frequency = …………… Hz [2]

5 [Turn over (ii) State Faraday’s Law of electromagnetic induction. ………………………………………………………………………………………………… …………………………………………………………………………………………..… [1] (iii) Use the laws of electromagnetic induction to explain why the amplitude of oscillation decreases after the switch is closed. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… …………………………………………………………………………………………..… [4] (b) The set -up in (a) is modified by suspending the magnet above the coil and adding an alternating voltage supply source in series with the coil and resistor, as shown in Fig .1.3. The frequency of the voltage source is set at 0.50 Hz. The magnet was at rest initially and starts oscillating when the switch is closed. Fig. 1.3 (i) State the frequency of oscillation of the magnet. frequency of oscillation = ………….. Hz [1]

6 (ii) The frequency of the voltage source is gradually increased to 5.0 Hz. State and explain what will be observed about the amplitude of oscillations of the magnet. ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………..…… [2] [Total: 10] 2 (a) Point source P, consisting of light with wavelength 630 nm, passes through a narrow slit and is incident on a screen at a distance of 2.4 m from the slit. Fig. 2.1 below shows the variation of intensity I of the light on the screen with distance x along the screen. Fig. 2.1 (i) Use Fig. 2.1 to determine the width of the slit. width = ………………………… mm [2] I x /mm

7 [Turn over (ii) State the effect on the pattern on the screen in terms of width and intensity of central maximum if each of the following changes is made separately: 1. the width of the single slit is reduced, ................................................................................................................................ ............................................................................................................................ [2] 2. the red source is replaced with another source of violet light of the same intensity. ................................................................................................................................ ............................................................................................................................ [2] (b) Light of wavelength 633 nm from a laser is directed normally at a diffraction grating, as illustrated in Fig. 2.2. Fig. 2.2 The diffraction grating is situated at the centre of a circular scale, marked in degrees. The readings on the scale for the second order diffracted beams are 160° and 188°. Calculate the number of lines per unit length of the slits in the diffraction grating. number of lines per unit length = ……………………………. m-1 [4] [Total: 10]

8 3 (a) Define electric potential. ................................................................................................................................................... ............................................................................................................................................... [1] (b) Fig. 3.1 shows a square ABCD of sides 2.0 cm. Three negative point charges of −1.2 C are fixed at B, C and D. Fig. 3.1 (i) (i) On Fig. 3.1, draw and label each of the forces acting on the charge at C due to the charges at B and D. [1] (ii) Determine the magnitude and direction of the resultant force acting on the charge at C due to the charges at B and D. magnitude = …………………….N direction = …………..……………. [3] A B C D O

9 [Turn over (iii) Determine the electric potential at the centre of the square , O, due to the three charges at B, C and D. electric potential = …………..…………….V [3] (iv) Determine the work done in bringing a positive charge of 1.2 C from 100 m away to the centre of the square. work done = …………..……………. J [2] [Total: 10]

10 4 (a) State two ways to increase the magnetic field strength of a solenoid. .…………………………………………………………………………………………………....…... .…………………………………………………………………………………………………....…... .…………………………………………………………………………………………..……….....[2] (b) The magnetic flux density in a solenoid is measured using a current balance. The current balance is a U-shaped piece of stiff wire ABCDEF pivoted at BE, as shown in Fig. 4.1. When in use, there is a turning force on the stiff wire caused by a current in CD. CD has length 25 mm, CB and DE each have length 106 mm. The stiff wire is first balanced when there is no current in it. A current of 4.9 A is then passed through CD and, in order to rebalance the stiff wire, a force of 5.7 × 10 -4 N is applied at a distance of 77 mm from the pivot, as shown in Fig. 4.2. which is the side view of the balance. Fig. 4.2 (side view) (i) On Fig. 4.1, indicate the direction of the current in CD. [1] (ii) Calculate the magnetic flux density in the solenoid. magnetic flux density = ........................................... full name of unit = .................................... [4] solenoid Fig. 4.1