Q.

Inductance of a coil with 104 turns is 10 mH and it is connected to a dc source of 10 V with internal resistance of 10Ω. The energy density in the inductor when the current reaches (1e) of its maximum value is απ×1e2J/m3. The value of α is ________.       (μ0=4π×10-7Tm/A) .                             [2026]


Ans.

(20)

L=10×10-3 H

N=104

I0=1010=1 A    (max current)

I=1e

Ed=B22μ0

B=μ0nI

L=μ0n2πR2

Ed=μ0n2I22

=4π×10-7×108×1e22

=20πe2