Question

A magnet of magnetic moment M is rotated through 360° in a magnetic field H, the work done will be

• A. MH
• B. 2MH
• C. $2 \pi M H$
• D. Zero

Answer 1

Answer: (D)

Zero

Answer 2

$W = M B \left( \cos \theta _ { 1 } - \cos \theta _ { 2 } \right) ; \theta _ { 1 } = 0 ^ { \circ }$ and $\theta _ { 2 } = 360 ^ { \circ }$ $\Rightarrow W = 0$