Question

A conducting circular loop of radius $r$ carries a constant current $i$. It is placed in a uniform magnetic field, such that is perpendicular to the plane of the loop. The magnetic force acting on the loop is.

Answer 1

Diagram

A diagram of a circular loop

1. $\times$ indicates a uniform magnetic field.
2. $dF$ is the magnetic force experienced by the loop.
3. $di$ is the uniform current flowing in the loop.

Concept

1. Magnetic force on a conductor in a magnetic field is perpendicular to the direction of the magnetic field and to the current flowing in that conductor.
2. The magnetic force in a conductor is given as $\overrightarrow{F}=i\left(\overrightarrow{dl}\times \overrightarrow{B}\right)$, where $i$ is current, $dl$ is distance between open ends of conductor and $B$ is magnetic field.
3. A circular loop has no open ends, it is a closed conductor therefore $l=0$ due to which magnetic force is also equal to zero.

The magnetic force on the circular loop is equal to zero.