In the given potentiometer circuit, the resistance of the potentiometer wire AB is R0. C is a cell of internal resistance r. The galvanometer G does not give zero deflection for any position of the jockey J. Which of the following cannot be a reason for this?
If e.m.f of C is greater than the e.m.f. of D,
Ir = 0
so r does not play any role of zero deflection in galvanometer.