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When a coil is connected across a 20 V dc supply, it draws a current of 5 A. When it is connected across 20 V, 50 Hz ac supply, it draws a current of 4 A. The self inductance of the coil is mH. (Take = 3)
10
On dc the inductor has no reactance: R = 205 = 4
On ac: Z = 204 = 5 = R2 + XL2 XL = 3
L = XL2 f = 32 3 50 = 0.01 H = 10 mH
Answer: 10
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