Question

The current in a coil changes from $0$ to $2$A in $0.05$s. If the induced emf is $80$V, the self-inductance of the coil, is?

• A. $1$H
• B. $0.5$H
• C. $1.5$H
• D. $2$H

Answer 1

The correct option is D $2$H

From the formula, $\epsilon =-L\frac{dI}{dt}$
Take magnitude on both sides.
$|\epsilon |=|-L\frac{dI}{dt}|$ or $\epsilon =L\frac{dI}{dt}$
$\therefore 80=L\left(\frac{2}{0.05}\right)\Rightarrow 80=L\times 40$
$\Rightarrow L=\frac{80}{40}\Rightarrow L=2H$.