A $12 \mathrm{V}$ battery connected to a coil of resistance $6 \Omega$ through a switch, drives a constant current in the circuit. The switch is opened in $1 \mathrm{ms}$. The emf induced across the coil is $20 \mathrm{V}$. The inductance of the coil is :

The current following through an inductance coil of self inductance $6 \mathrm{mH}$ at different time instants is as shown. The emf induced between $t=20 \mathrm{s}$ and $t=40 \mathrm{s}$ is nearly

In a circuit current decrease from $5A$ to $0A$ is $0·1s$. If the average induced e.m.f is $200v$, calculate the self inductance of the circuit and write is unit.

Current in a coil with self-inductance $2 \mathrm{H}$ is increasing according to$I=\left(2{\mathrm{sint}}^2\right)$ ampere. Amount of energy spent during the period when current changes from $0$ to $2 \mathrm{A}$ is $\underline{ }$