Question

An average induced emf of $0.20\text{V}$ appears in a coil when the current in it is changed from $5\text{A}$ in one direction to $5\text{A}$ in the opposite direction in $0.20\text{s}.$ The self-inductance $\left(\text{in mH}\right)$ of the coil is
(Give integer value only)

Answer 1

Given:
$E=0.2\text{V};i_1=5\text{A}$
$i_2=-5\text{A}(\because$ direction of current is reversed)

Using,

$E=-L\frac{\Delta i}{\Delta t}$

$\Rightarrow 0.2=-L\times \frac{\left[\right(-5)-5]}{0.2}$

$\therefore L=0.004\text{H}=4\text{mH}$