Question

While doing an experiment with potentiometer (figure) it was found that the deflection is one sided and (i) the deflection decreased while moving from one end A of the wire, to the end R; (ii) the deflation increased, while the jockey was removed towards the end D.
Which terminal positive or negative of the cell $E_1$ is connected at X in case
(i) and how is $E_1$ related to E?
(ii) Which terminal of the cell $E_1$ is connected at X in case (ii)?

Answer 1

(i) If the current in auxiliary circuit (lower circuit containing primary cell) decreases, and potential difference across A and jockey/increases. Then deflection in galvanometer is one sided and the deflection decreased, while moving from one end ‘A ’ of the wire to the end ‘S’.
And clearly this is possible only when positive terminal of the cell E₁ is connected at X and E₁>E.
(ii) If the current in auxiliary circuit increases, and potential difference across A and jockey J increases. Then also deflection in galvanometer is one sided.
And this is possible only when negative terminal of the cell E₁ is connected at X.