Q. A magnet of magnetic moment 20 CGS units is freely suspended in a uniform magnetic field of intensity 0.3 CGS units. The amount of work done in deflecting it by an angle of $30{^\circ}$ in CGS units is
A) $6$
B) $3\sqrt{3}$
C) $3(2 - \sqrt{3})$
D) 3
Explanation
(c) Work done, $W = MB.\left( 1 - \cos\theta \right)$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = 20 \times 0.3(1 - \cos{30{^\circ}})$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = 6\left( 1 - \frac{\sqrt{3}}{2} \right) = 3\left( 2 - \sqrt{3} \right)$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.