Two galvanometers, A and B, require currents of 2 mA and 5 mA, respectively, to produce the same deflection of n divisions. Then
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A is more sensitive than B
The current sensitivity of a galvanometer is the deflection produced per unit current. A galvanometer that needs a smaller current for the same deflection is more sensitive.
\( \displaystyle S_A = \frac{n}{2\,\mathrm{mA}} \)
\( \displaystyle S_B = \frac{n}{5\,\mathrm{mA}} \)
\( \displaystyle \frac{S_A}{S_B} = \frac{n/2}{n/5} = \frac{5}{2} \)
So A is 5/2 times as sensitive as B.
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,
\( \displaystyle \frac{\phi}{I} = \frac{NAB}{k} \qquad (4.27) \)”