A thin stiff insulated metal wire is bent into a circular loop with its two ends extending tangentially from the same point of the loop. The wire loop has mass \( m \) and radius \( r \) and it is in a uniform vertical magnetic field \( B_0 \), as shown in the figure. Initially, it hangs vertically downwards, because of acceleration due to gravity \( g \), on two conducting supports at \( P \) and \( Q \). When a current \( I \) is passed through the loop, the loop turns about the line \( PQ \) by an angle \( \theta \) given by
