GESS 2026 Physics P3 MS

This paper consists of 15 pages including the cover page. MARKING SCHEME

GESS 4EXP PHY P3 Prelim 26 TYL 2 Section A 1 In this experiment, you will determine a value for the focal length of a thin convex lens. You are provided with: • a convex lens • a lens holder • illuminated cross wires (object) • a lamp • a screen • a metre rule • a piece of Blu-tack • a stand, a boss and a clamp. You will assemble the apparatus as shown in Fig. 1.1. Fig. 1.1 (a) Setting up the apparatus 1. Secure the metre rule to the bench with two small pieces of Blu-tack. Place one small piece under each end of the rule and press the rule firmly onto the bench. 2. Place the cross wires, lens holder and screen behind the rule so that they touch it. It is important that you are able to read the position on the rule of each of them. 3. Place the cross wires at the 0.0 cm position on the rule. Once in this position, the cross wires must not be moved.

GESS 4EXP PHY P3 Prelim 26 TYL 3 4. The lens holder with the lens, and the screen are to be positioned as described in the instructions given in parts (b)(i) and (b)(ii). 5. Turn on the lamp close to the left of the cross wires so that light passes through the cross wires and lens, and shines on the screen. (b) (i) 1. Position the screen so that it is at the 90.0 cm mark on the metre rule. This is distance D. 2. Start with the lens close to the cross wires. Move the lens towards the screen until a sharp image of the cross wires is observed on the screen. This is position A. 3. The distance of the lens from the cross wires is UA. Record UA. Calculate 1/UA. UA = 0.181 m 1/UA = 5.52 m-1 *[B1] based on student’s answer where UA is to 3 d.p. in m / 1 d.p. in cm, 1/UA to 3 S.F. and correct units for UA and 1/UA 4. Without moving the cross wires or screen, move the lens closer to the screen until a second sharp image is observed. This is position B. 5. The distance of the lens from the cross wires is UB. Record UB. Calculate 1/UB. UB = 0.718 m 1/UB = 1.39 m-1 *[B1] based on student’s answer where UB is to 3 d.p. in m / 1 d.p. in cm, 1/UB to 3 S.F. and correct units for UB and 1/UB (ii) Position the screen at 85. 0 cm mark on the metre rule ( D = 85.0 cm). Repeat the instructions (b)(i)2 to 5(b)(i) and record UA and UB. Calculate 1/UA and 1/UB. UA = 0.188 m 1/UA = 5.32 m-1 *[B1] based on student’s answer where UA is to 3 d.p. in m / 1 d.p. in cm, 1/UA to 3 S.F. and correct units for UA and 1/UA UB = 0.610 m 1/UB = 1.64 m-1 *[B1] based on student’s answer where UB is to 3 d.p. in m / 1 d.p. in cm, 1/UB to 3 S.F. and correct units for UB and 1/UB *Don’t penalise the same mistake more than once.

GESS 4EXP PHY P3 Prelim 26 TYL 4 (c) Determine gradient of the line passing through the coordinates (1/UB, 1/UA) that you have obtained in (b)(i) and (b)(ii). gradient = (5.52 – 5.32) / (1.39 – 1.64) = -0.800 gradient = -0.800 [B1] for showing working, [B1] for calculating correctly based on student’s values (to 3 S.F.) (d) Use the magnitude of the gradient and the formula below to determine a value for the focal length, f, of your lens. f = 100 / [(1.2  0.800) + 5.72] = 15.0 f = 15.0 cm [B1] for showing working, [A1] for the value of f between 13.5 cm and 16.5 cm (to 3 S.F.) (f) On Fig. 1.2, draw a ray diagram to show the formation of the image you obtained at position A in part (b)(i). The focal points of the lens are marked and labelled with F on the diagram. The diagram is not drawn to scale. Fig. 1.2 [B1] for drawing the light rays correctly with arrows

GESS 4EXP PHY P3 Prelim 26 TYL 5 (f) Identify one possible source of error in this experiment. Suggest an improvement that would reduce this error. source of error Image is too small to be observed for D improvement Use shorter D to obtain larger image / Use a lens with shorter focal length [B1] for correct source of error and corresponding improvement [Total: 10]

GESS 4EXP PHY P3 Prelim 26 TYL 6 2 In this experiment, you will investigate an electrical circuit. You are provided with: • two 1.5 V dry cells in holders • a voltmeter • a switch • a resistor R • a resistance wire attached to a metre rule • seven connecting leads with crocodile clips at both ends • a connecting lead labelled ‘C’ • a digital micrometer. (a) Set up the circuit as shown in Fig. 2.1. Fig. 2.1 The distance between the two crocodile clips is L. Adjust the position of the crocodile clip C so that L is about 0.60 m. Close the switch. Measure and record L and the voltmeter reading V. Open the switch. L = 0.600 m V = 1.40 V [1] [B1] based on student’s value with L around 0.600 m or 60.0 cm and V to 2 d.p. ending with 0 or 5

GESS 4EXP PHY P3 Prelim 26 TYL 7 (b) Determine an accurate value for the thickness d of the resistance wire. d1 / mm d2 / mm <d> / mm 0.310 0.315 0.313 [B1] for measuring diameter at more than one position of the resistance wire [B1] for calculating <d> and record to 3 d.p. d = 0.313 mm [2] (c) Calculate the cross-sectional area A of the resistance wire where A = ¼ d 2. A = ¼ d 2 = ¼  (0.313  10-3)2 = 7.69  10-8 m2 [B1] for showing working and correct calculation to 3 S.F. with unit A = 7.69  10-8 m2 [1] 0.0769 mm2 is also acceptable (d) A student claims tha t , where b is a constant and V is the voltmeter reading. Plan an experiment to investigate the student’s claim. In your plan, you should: • explain briefly how to do the experiment • state one key variable to control • draw a table, with column headings, to show how to display the range of readings • explain how to determine R and b if the student’s claim is correct , given  is a constant with a value of 1.5  10-6  m. Constant variables: thickness of resistance wire, electromotive force of the power supply [B1] Set up the apparatus as shown in Fi g. 2.1. Record the readings from (a) to (c). Repeat (a) for five different lengths of L. Calculate V / L for every different length of L. [B1] Tabulate the readings of L, V and (V/L) as shown below.

GESS 4EXP PHY P3 Prelim 26 TYL 8 L / m V / V / V m-1 0.150 0.300 0.450 0.600 0.750 0.900 [B1] for correct headings with units [B1] for six readings of L with wide range (at least 70.0 cm apart) Plot a graph of against V where gradient = and V-intercept = b. [B1] R = -  / (A  gradient) = - (1.5  10-6) / (A  gradient) [B1] [Total: 10]

GESS 4EXP PHY P3 Prelim 26 TYL 9 BLANK PAGE

GESS 4EXP PHY P3 Prelim 26 TYL 10 Section B 3 In this experiment, you will investigate the extension of two springs connected in parallel. You are provided with: • a stand, boss and clamp • two springs • two wooden rods • 100 g mass hanger • two 50 g masses • two 100 g mass • a string loop • a metre rule. (a) You are provided with two springs. The length of each unstretched spring between the centres of the loops is l, as shown in Fig. 3.1. Fig. 3.1 Measure and record l for each of the provided springs. l for first spring = 4.0 cm l for second spring = 4.0 cm [B1] for l to 1 d.p. in cm / 3 d.p. in m; 3.6 cm < l < 4.4 cm Determine the mean length L of the two springs. L = (4.0 + 4.0) / 2 = 4.0 cm L = 4.0 cm [B1] for calculating L and record to 1 d.p. in cm / 3 d.p. in m