In the shown circuit, no current flows through the galvanometer. If the cross-sectional diameter of wire AB is doubled, find the new value of AC required for the null point.

Question

G1 Physics · Accepted Answer

At balance, the resistance ratio equals the wire-length ratio. Doubling the diameter reduces the resistance per unit length of AB by a factor of 4 but does so uniformly along the entire wire, so the balance fraction is unchanged. Hence AC remains x, option A.