The back e.m.f. induced in a coil, when current changes from 1 ampere to zero in one millisecond, is 4 volts. The self-inductance of the coil is

Question

The back e.m.f. induced in a coil, when current changes from 1 ampere to zero in one millisecond, is 4 volts. The self-inductance of the coil is (A) 1 H (B) 4 H (C) 10-3 H (D) 4 × 10-3 H

Tardigrade Admin · Accepted Answer

e=-L (d i/d t) ; But e=4 V and (d i/d t)=(0-1/10-3)=-1 / 10-3 ∴ (-1/10-3)(-L)=4=L=4 × 10-3 H

Q. The back e.m.f. induced in a coil, when current changes from $1$ ampere to zero in one millisecond, is $4$ volts. The self-inductance of the coil is

$1 H$

$4 H$

$1 0^{- 3} H$

$4 \times 1 0^{- 3} H$

$e = - L \frac{d i}{d t};$ But $e = 4 V$
and $\frac{d i}{d t} = \frac{0 - 1}{1 0 ^{- 3}} = - 1/1 0^{- 3}$
$∴ \frac{- 1}{1 0 ^{- 3}} (- L) = 4 = L = 4 \times 1 0^{- 3} H$

Q. The back e.m.f. induced in a coil, when current changes from 1 ampere to zero in one millisecond, is 4 volts. The self-inductance of the coil is

1H

4H

10−3H

4×10−3H