Q. A square shaped coil of area $70\ \mathrm{cm^2}$ having $600$ turns rotates in a magnetic field of $0.4\ \mathrm{Wb\ m^{-2}}$, about an axis which is parallel to one of the side of the coil and perpendicular to the direction of field. If the coil completes $500$ revolution in a minute, the instantaneous emf when the plane of the coil is inclined at $60^{\circ}$ with the field, will be ______ $\mathrm{V}$. (Take $\pi=\frac{22}{7}$)