2023 RI H2 Physics Prelims P4 Answers

1 ©Raffles Institution 9749/04 H2 Physics Prelim P4 (2023) Suggested solutions 1 In this experiment, you will investigate an electrical circuit. (a) Set up the circuit as shown in Fig. 1.1. Fig. 1.1 H is a crocodile clip that is free to move along the wire. Y is a resistor with resistance R. (b) Adjust length L to approximately 0.10 m. Measure and record L. L = 0.100 m (c) Close the switch. Measure and record the current I and the potential difference V. I = 85.93 mA V = 1.0135 V [1] Marker’s comments: • Many candidates converted current from mA to A wrongly which carried over to their table readings and calculations being wrong. • A small number of candidates connected the wires wrongly and ended up with wrong values/trend for the table values. • A significant number of candidates manipulated the equation wrongly, e.g., decided to plot V against L, without realising that it is not a linear relationship. A V H metre rule tape tape wire L Y

2 ©Raffles Institution 9749/04 (d) Repeat (b) and (c) for different values of L by varying the position of H. L /m I /mA V /V V I / 0.100 85.93 1.0135 11.79 0.200 80.65 1.0376 12.87 0.300 75.98 1.0715 14.10 0.400 71.20 1.0936 15.36 0.500 68.04 1.1116 16.34 0.600 64.17 1.1221 17.49 0.690 61.32 1.1393 18.58 [4] (e) V and L are related by the expression V R k L=+II where k is a constant. Plot a suitable graph to determine R and k. VV R k L R kL= +  = +II I Plot a graph of V I against L, where the gradient is k and the vertical intercept is R. Gradient 19.60 11.90 7.70 11.5 (3 s.f.)0.780 0.110 0.670 −= = = − 111.5 mk − =  From graph, vertical intercept = 10.65  10.65 R =  OR Using (0.780, 19.60) and gradient = 11.5 ( )( )19.60 11.5 0.780 10.63 C C =+ = 10.63 R =  R = 10.65  k = 11.5  m–1 [6] [Total: 11]

3 ©Raffles Institution 9749/04 /V I 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.0 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 (0.110,11.90) (0.780,19.60) anomally L / m

4 ©Raffles Institution 9749/04 2 In this experiment, you will investigate the equilibrium of a metre rule. (a) (i) You have been provided with a metre rule with a spring attached, as shown in Fig. 2.1. Fig. 2.1 (ii) The length of the unstretched spring is L0, as shown in Fig. 2.2. Fig. 2.2 Measure and record L0. L0 = 4.2 cm [1] (b) Set up the apparatus as shown in Fig. 2.3. Fig. 2.3 The metre rule is placed on top of one of the rods. The distance x between the hole with the string and the centre of the rod is shown in Fig. 2.3. Set x to be about 50 cm and adjust the apparatus until the metre rule is horizontal