A moving coil of galvanometer when shunted with 2 , resistance gives a full scale deflection for a current of 500 mA. When a resistance of 470 , is connected in series it gives a full scale deflection for 10 V potential applied on it. The value of resistance of galvanometer coil is __________ .

Step-by-step solution

Let G be the resistance of the galvanometer and I_g be the current required for full scale deflection. When the galvanometer is shunted with S = 2 , , it acts as an ammeter of range I = 500 mA = 0.5 A . The potential difference across the galvanometer and the shunt is equal: I_g G = (I - I_g) S I_g G = (0.5 - I_g) 2 I_g G + 2 I_g = 1 I_g = 1 G + 2 When a resistance R = 470 , is connected in series, it acts as a voltmeter of range V = 10 V . The total voltage is the sum of the voltage drops: V = I_g (G + R) 10 = I_g