A constant voltage is applied to a series - circuit by closing a switch

PHYSICS · Single correct · CBSE · Physics · Electromagnetic Induction · Electromagnetic Induction

Problem

A constant voltage is applied to a series

R

L

circuit by closing a switch. The voltage across the inductor, where

L=2\,\mathrm{H}

, is

20\,\mathrm{V}

t=0

and drops to

5\,\mathrm{V}

t=20\,\mathrm{ms}

. The value of

R

is (a)

100\ln2\,\Omega

(b)

100(1-\ln2)\,\Omega

(c)

100\ln4\,\Omega

(d)

100(1-\ln4)\,\Omega