The metal rod of length  $\mathcal{l}=0.2m$  hung horizontally on two light insulating on two light insulating wires of length L = 0.1 m in the vertical magnetic field with induction B = 1 Tesla. It is initially at  $\alpha ={60}^0$ from the equilibrium position and released (Fig.). Find the potential difference between the ends of the rod at a time when it passes the lowest position