Question

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.)

• A. $-1.25\times {10}^{-4}J$
• B. $-2.51\times {10}^{-4}J$
• C. $2.51\times {10}^{-4}J$
• D. $1.25\times {10}^{-4}J$

Answer 1

The correct option is C $2.51\times {10}^{-4}J$

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 $\mu .B=-\mu B$

$⟹$ $P.E=\mu B$

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