Question

A rectangular current loop having magnetic moment M is in an arbitrary orientation in a uniform external magnetic field B. The loop is rotated through 180° about an axis passing through its centre and perpendicular to its plane. Work done is - (a) zero(b) MB(c) -MB(d) 2MB

Answer 1

Dear Student,

$$\begin{gathered} workdone+veaswerotatedtheloopinducedcurrentdeveloped. \\ torqueontheloop=MB\sin \theta \\ dw={\int }_0^{\mathrm{\pi }}MB\sin \theta d\theta =-MB{\left|\cos \theta \right|}_0^{\mathrm{\pi }}=2MB \\ optiond \\ Regards \end{gathered}$$