A square frame of side 'L' carries a current I. The magnetic field at its centre is B. The same current is passed through a circular coil having the same perimeter as the square. The magnetic field at the centre of the circular coil is B′. The ratio of \(\frac{B}{B'}\) is:
1
\(\rm\frac{8\sqrt{2}}{\pi^2}\)
2
\(\rm\frac{8\sqrt{2}}{\pi^3}\)
3
\(\rm\frac{8\sqrt{2}}{\pi}\)
4
\(\rm\frac{4\sqrt{2}}{\pi^2}\)