A moving coil galvanometer has 50 turns and each turn has an area 210 . The magnetic field produced by the magnet inside the galvanometer is 0.02 . The torsional constant of the suspension wire is 10 . When a current flows through the galvanometer, a full scale deflection occurs if the coil rotates by 0.2 . The resistance of the coil of the galvanometer is 50 . This galvanometer is to be converted into an ammeter capable of measuring current in the range 01.0 . For this purpose, a shunt resistance is to be added in parallel to the galvanometer. The value of this shunt resistance, in , is __________.

Answer

`5.56`

Explanation

`N = 50, A = 2 xx 10^(-4) m^(2) , C = 10^(-4) , R = 50 Omega`,
` B = 0.02 T , theta = 0.2 ` rad
` Ni AB = C theta`
` i_(g) = (C theta)/(N AB) = (10^(-4) xx 0.2)/(50 xx 2 xx 10^(-4) xx 0.02) = 0.1 A`
Now when shunt is connected, then we can write as follows:
` i_(g) xx G = (i - i_(g)) S`
` 0.1 xx 50 = (1 - 0.1) xx S`
` 5 = 50/9 = 5.56 Omega`