Physics - Magnetism Question with Solution | TestHub

Torque due to magnetic field${\tau }_{\text{mag}}={\text{MB}}_0=\text{I}\pi {\text{R}}^2{\text{B}}_0$...(i)

Torque due to weight about the point where string is connected${\tau }_{\text{weight}}=\text{mgR}$...(ii)

If ring remains horizontal, then${\tau }_{\text{mag}}{=\tau }_{\text{weight}}$

$\text{I}\pi {\text{R}}^2{\text{B}}_0=\text{mgR}\Rightarrow \text{I}=\frac{\text{mg}}{\pi {\text{RB}}_0}$