Question

If the current is doubled, the deflection is also doubled in

(a) a tangent galvanometer
(b) a moving-coil galvanometer
(c) both
(d) none

Answer 1

(b) a moving coil galvanometer

The current and deflection dependence of a moving coil galvanometer is given by
$i=\frac{k}{nAB}\theta \Rightarrow i\propto \theta$
Therefore, if we double the current, the deflection also gets doubled.
However, in a tangent galvanometer, $i\propto \tan \theta$; that is, there is no direct relation between $\theta$ and current.
Hence, the correct option is (b).