Two coils have mutual inductance $0.002 \mathrm{~H}$. The current changes in the first coil according to the relation $\mathrm{i}=\mathrm{i}_0 \sin \omega \mathrm{t}$, where $\mathrm{i}_0=5 \mathrm{~A}$ and $\omega=50 \pi$ rad/s. The maximum value of emf in the second coil is $\frac{\pi}{\alpha} \mathrm{~V}$. The value of $\alpha$ is _______.