Question

An elastic circular wire of length $l$ carries a current 1. It is placed in a uniform magnetic field B (out of paper) such that its plane is perpendicular to the direction of B. The wire will experience

• A. no force
• B. a stretching force
• C. a compressive force
• D. a torque

Answer 1

Answer: (A)

Angle between normal to plane and B is $90{}^{\circ }$ . Because plane of circular wire is perpendicular to B. $F=Bil\sin \theta$ $=Bil\sin \theta$ $=0$