The magnetic moment of a current carrying loop is $\mu =6.25\times {10}^{-4}A{m}^2$ and a magnetic field of value $0.4T$ is applied in upward direction perpendicular to the plane of loop.Find the potential energy of loop in magnetic field in joules. (The direction of current in loop is in clockwise direction.)

As the direction of the current in the loop is clockwise, thus magnetic moment points in the downward direction.

$\therefore$ Magnetic moment $\mu =6.25\times 10^{-4}A{m}^2$ (downwards)

Magnetic field $B=0.4T$ (upwards)

Potential energy of loop $P.E=-\mu .B$

As $\mu$ and $B$ are anti-parallel, thus $\mu .B=-\mu B$

$⟹$ $P.E=\mu B$

$\therefore$ $P.E=6.25\times 10^{-4}\times 0.4=2.5\times 10^{-4}$ $J$