question_answer

A circular coil having N turns and radius r carries a current I. It is held in the XZ plane in a magnetic field \[B\hat{i}\]. The torque on the coil due to the magnetic field is:      [JEE Main 8-4-2019 Morning]

A) \[B\pi {{r}^{2}}IN\]

B) \[\frac{B{{r}^{2}}I}{\pi N}\]

C) Zero     

D) \[\frac{B\pi {{r}^{2}}I}{N}\]

Correct Answer: A

Solution :

[a]

Magnetic moment of coil

Torque on loop (coil)