Question

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

• A. No force
• B. A stretching force
• C. A compressive force
• D. A torque

Answer 1

The correct option is B A stretching force

Consider any small segment of the wire and try finding the direction in which the magnetic force acts on it.
By F=idlXB, the magnetic force acts radially outwards. Now if you sum up the effects on all of the infitisimal segments, evidently it tries to stretch the wire.