Question

An emf of $5\text{V}$ is produced by an inductor due to self inductance, when the current changes at a steady rate from $3\text{A}$ to $2\text{A}$ in $1\text{ms}$. The value of self inductance of inductor is

• A. $\text{Zero}$
• B. $0.5\text{H}$
• C. $50\text{H}$
• D. $5\text{mH}$

Answer 1

The correct option is D $5\text{mH}$

The emf produced across an inductor is,
$\epsilon =-L\frac{di}{dt}...\left(i\right)$
$\frac{di}{dt}=$rate of change of current through inductor.
$\Rightarrow \frac{di}{dt}=\frac{2-3}{1\times {10}^{-3}}=-1000{\text{As}}^{-1}$
Substituting in Eq $\left(i\right)$,
$5=-L\times (-1000)$
$\therefore L=5\times {10}^{-3}\text{H}=5\text{mH}$