Question

Current in a circuit falls from $5.0A$ to $0.0A$ in $0.1sec$. If an average emf of $200V$ is induced, give an estimate of the self-inductance of the circuit.

Answer 1

Change in current, $\Delta I=0.0-5.0=-5.0$ $A$

Rate of change of current, $\frac{\Delta I}{\Delta t}=\frac{-5.0}{0.1}=-50.0$ $A/s$

Average induced emf, $E=200$ $V$

Using $E=-L\frac{\Delta I}{\Delta t}$ where $L$ is the self inductance of circuit

$\therefore$ $200=-L\times (-50.0)$

$⟹$ $L=4.0$ $H$