Rotational magnetic damping of a square wire loop
= Rotational magnetic damping of a square wire loop
A thin square loop rotating about a central in-plane axis has $\mathcal I=ma^2/6$. With ohmic current and decay slow compared with a rotation, the averaged torque is $-B^2a^4\omega/(2R)$. Its angular-speed decay time is $mR/(3B^2a^2)$; its kinetic-energy decay time is half that value.