A circular coil of radius 5 cm has 500 turns of a wire. The approximate value of the coefficient of self-induction of the coil will be
25 mH
25×10-3mH
50×10-3mH
50×10-3H
ϕ=Li⇒NBA=Li
Since magnetic field at the centre of circular coil carrying current is given by B=μ04π·2πNir
∴ N·μ04π·2πNir·πr2=Li⇒L=μ0N2πr2
Hence, self-inductance of a coil
=4π×10-7×500×500×π×0.052=25 mH