When 0.005A current flows through a moving coil galvanometer, it gives full scale deflection. It is converted into a voltmeter to read 5 Volt, using an external resistance of 975Ω. The resistance of galvanometer in ohms is

Given that a current of 0.005A gives full scale deflection in a moving coil galvanometer. When it is converted into a voltmeter to read 5V, using an external resistance of 975Ω. We need to find the resistance of the galvanometer in ohms.
Let the resistance of the galvanometer be GΩ. The current flowing through the galvanometer is 0.005A. When it is converted into a voltmeter, the current flowing through the circuit is given by Ohm's law as

$I=\frac{V}{R_G+R_E}$

We know that the voltmeter reads 5V and the external resistance is 975Ω. Therefore, we can write

$0.005=\frac{5}{G+975}$

$G=\frac{5}{0.005}-975$

$G=1000-975$

$G=25$

Hence the correct answer is 25.