A potentiometer circuit is employed to find the electromotive force (e.m.f.) $E_X$ of a cell. The arrangement has a second cell with known e.m.f. $E_0$ and negligible internal resistance, together with a uniform resistance wire $PQ$ whose length is known. $E_X$ is smaller than $E_0$. The sliding contact $J$ may be placed at any point along the resistance wire. Which circuit is appropriate for finding $E_X$?
Physics 9702 · AS & A Level · Practical circuits