Physics (AS & A Level) · May / June 2021 · Paper 13 · Question 38

In the circuit shown, a potentiometer of total resistance 120 Ω is connected in parallel with a resistor of resistance 150 Ω and a resistor of resistance R. The battery has electromotive force (e.m.f.) 12 V and negligible internal resistance. [circuit diagram] The voltmeter reads 0 V when the slider of the potentiometer is 1/4 of the way from its lower end, as shown. What is resistance R?

1. A30 Ω
2. B38 Ω
3. C50 Ω
4. D450 Ω

As printed in the paper