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