A massless square loop, of wire of resistance 10 D . supporting a mass of I g . hangs vertically with one of its sides in a uniform magnetic field of $10^3 \mathrm{G}$, directed outwards in the shaded region. A dc voltage V is applied to the loop. For what value of $\mathrm{V}_{\text {and }}$ the magnetic force will exactly balance the weight of the supporting mass of lg ? (If sides of the loop $=10 \mathrm{~cm}, \mathrm{~g}=10 \mathrm{~ms}^{-}$)