Question

Figure (a) below shows a Wheatstone bridge in which P, Q, R, S are fixed resistances, G is a galvanometer and B is a battery. For this particular case the galvanometer shows zero deflection. Now, only the i positions of B and G are interchanged,. as shown in the figure (b). The new deflection of the galvanometer

• A. is to the left.
• B. is to the right.
• C. is zero
• D. depends on the values of P, Q, R, S

Answer 1

The correct option is C is zero

Answer is C.
In the first case, the deflection in the galvanometer is the zero as there is no current flow through the galvanometer in a balanced Wheatstone bridge because, in the balanced state, the voltage on both terminals of the galvanometer is the same. Since the voltage differential in zero, there can be no current.
In the second case, the positions of the battery and galvanometer are interchanged, which makes no difference in the voltage difference as the values of resistances and battery remain the same.
Hence, the new deflection of the galvanometer will be zero.