(a) Current sensitivity of galvanometer: Current sensitivity of galvanometer $=\frac{\theta}{I}=N B A / c$ So, to increase the current sensitivity: (i) Permanent magnet should be strong so that $B$ is high. (ii) $N$ and $A$ should be high. (iii) Value of $c$ must be low. (b) To convert into a voltmeter of range $(0-V)$, $V=I_g(R_g+R_1)$ .....(i) To convert into a voltmeter of range $(0-2V)$, $2V=I_g(R_g+R_2)$ .....(ii) Dividing equation (i) by (ii) $\frac{V}{2V} = \frac{R_g+R_1}{R_g+R_2}$ $\text{ Or, } \frac{1}{2} = \frac{R_g+R_1}{R_g+R_2}$ $\therefore R_g = R_2 - 2R_1$