A wire of length l is bent in the form of a circular loop with a no of turns and is suspended in a magnetic field of intensity B. Find the expression for the maximum torque produced on the circular loop when a current I is passed through it. 

Asked by mridulabarua05 | 20th Feb, 2019, 05:08: PM

Expert Answer:

This question is very similar to concept of moving coil galvanometer.
In moving coil galvanometer we first find the force acting on loop by the external magnetic field.
Since the loop area vector is along the direction of magnetic field the the force acting on the whole loop is
F = I(2πr)B where r is radius of loop and I is the current 
Now if the loop is hinged at two diametric opposite point so torque provided by these force work as a couple and it will rotate the loop in a particular direction 
So torque = F×r = 2πr^2IB.

Answered by Ankit K | 21st Feb, 2019, 11:00: AM