A coil of circular cross-section having $1000$ turns and $4 {\mathrm{cm}}^2$ face area is placed with its axis parallel to a magnetic field which decreases by ${10}^{-2} \mathrm{Wb} {\mathrm{m}}^{-2}$ in $0.01 \mathrm{s}$. The e.m.f. induced in the coil is :