The current sensitivity of a galvanometer is

The correct answer is Option (3) → is inversely proportional to torsional constant of the spring.

In a moving coil galvanometer the magnetic torque balances the restoring torque of the spring.

    \( \displaystyle NIAB = k\phi \)

Current sensitivity is the deflection per unit current:

    \( \displaystyle \frac{\phi}{I} = \frac{NAB}{k} \)

So it is directly proportional to N, A and B, and inversely proportional to the torsional constant k.

NCERT (2026-27):
The Moving Coil Galvanometer – “… We define the current sensitivity of the galvanometer as the deflection per unit current. From Eq. (4.26) this current sensitivity is,

    \( \displaystyle \frac{\phi}{I} = \frac{NAB}{k} \qquad (4.27) \)

A convenient way for the manufacturer to increase the sensitivity is to increase the number of turns \( N \).”