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 and A of the wire, to the end R, (ii) the deflection increased, while the jockey was moved towards the end D.
(i). 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 (1 in 1)?

Options

A. `E gt E_(1)` and `+ve` terminal of `E_(1)` is connected to X
B. `E lt E_(1)` and `-ve` terminal of `E_(1)` is connected to X
C. `E gt E_(1)` and `-ve` terminal of `E_(1)` connected to X
D. `E lt E_(1)` and `+ve` terminal of `E_(1)` is connected to X

Answer

B

Explanation

(i) The deflection in the galvanometer is one sided i.e. the balance point is not obtained on the wire AB. This happends, because the P.D. across the wire is less than the emf of the cell `E_(1)`. Hence, `E lt E_(1) or E_(1) gt E`.
(ii) The deflection in G is increased, while moving the jockey from A to B. This shows that the current in the secondary circuit, containing the cell of emf `E_(1)`, is incrased. This is possible only when the `-ve` terminal of `E_(1)` is connected at X.
Thus `E lt E_(1)` and the negative terminal of `E_(1)` is connected to X.