Moving Charges and Magnetism

A current of 200 deflects the coil of a moving coil galvanometer through 60 . The current to cause deflection through 10 radian is :

1. 120
2. 180
3. 30
4. 60

Answer

(4) 60

Solution

Moving coil galvanometer: NIAB=k I

In the radial field the deflecting torque balances the restoring torque k of the spring.

1=60 = 3 rad

I2I1= 2 1= /10 /3= 310

I2= 310 200=60

Answer: (4)