Q. Potential energy of a bar magnet of magnetic moment $M$ placed in a magnetic field of induction $B$ such that it makes an angle $\theta$ with the direction of $B$ is
A) $MB\ sin\ \theta$
B) $- MB\ cos\theta$
C) $MB(1 - \ cos\theta)$
D) $MB(1 + \cos\theta)$
Explanation
(b) PE$= - MB(\cos\theta_{2} - cos\theta_{1})$
When $\theta_{1} = 90{^\circ}$ (position of zero PE), $\theta_{2} = \theta$
PE$= - MB$ $cos\theta$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.