Explanation

(a) For a tangent galvanometer
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ B = B_{H}\tan\theta$
Here, $\ \ B = \frac{\mu_{0}}{4\pi}\frac{2\pi ni}{a}\ \Rightarrow \frac{\mu_{0}}{4\pi}\frac{2\pi\ ni}{q} = B_{H}\tan\theta$
or $\theta \propto n$
$\therefore$ If the number of turns in the coil are doubled, the deflection will increase.