Question

A magnetic dipole of magnetic moment M is rotated through ${360}^o$ in a magnetic field B.
The work done is

• A. 2 MB
• B. $\frac{MB}{2}$
• C. zero
• D. Infinity

Answer 1

Answer: (C)

zero

Work done, $W=MB(cos\theta -1-cos{\theta }_2)$
Given, we have
$W=MB[cos\theta -1-cos({360}^0+{\theta }_1\left)\right]$
$W=MB[cos\theta -1-cos{\theta }_1]=0$