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 B; (ii) the deflection increased. while the jockey was moved towards the end B.

1. Which terminal + or – ve of the cell E₁, is connected at X in case (i) and how is E₁ related to E?
2. Which terminal of the cell E₁ is connected at X in case (ii)?

Answer 1

1. 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 decreases 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.
2. 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.