Physics (AS & A Level) · Oct / Nov 2025 · Paper 12 · Question 36

A potentiometer circuit is used to determine the electromotive force (e.m.f.) $E_X$ of a cell. The circuit includes a second cell of known e.m.f. $E_0$ and negligible internal resistance, and a uniform resistance wire PQ of known length. $E_X$ is less than $E_0$. The movable connection J can be positioned anywhere along the length of the resistance wire. Which circuit is suitable for determining $E_X$?

1. ACircuit A
2. BCircuit B
3. CCircuit C
4. DCircuit D

As printed in the paper