Alternating Current

When a d.c. voltage of \(200 \mathrm{~V}\) is applied to a coil of self-inductance \(\left(\frac{2 \sqrt{3}}{\pi}\right) \mathrm{H}\), a current of \(1 \mathrm{~A}\) flows through it. But by replacing d.c. source with a.c. source of \(200 \mathrm{~V}\), the current in the coil is reduced to \(0.5 \mathrm{~A}\). Then the frequency of a.c. supply is