The current sensitivity of a galvanometer is defined as the deflection produced when unit current passes through the galvanometer. A galvanometer is said to be sensitive if it produces large deflection for a small current.
In a galvanometer, I = (C/nBA) x θ
∴ Current sensitivity θ/I = nBA/C … (1)
The current sensitivity of a galvanometer can be increased by
(i) increasing the number of turns
(ii) increasing the magnetic induction
(iii) increasing the area of the coil
(iv) decreasing the couple per unit twist of the suspension wire.
This explains why phosphor-bronze wire is used as the suspension wire which has small couple per unit twist.