An $LR$ circuit with a battery is connected at $t = 0$. Which of the following quantities is not zero just after the circuit is closed?

An inductor of $10\, \text{mH}$ is connected to a $20\, \text{V}$ battery through a resistor of $10\, \text{k}\Omega$ and a switch. After a long time,when maximum current is set up in the circuit,the current is switched off. The current in the circuit after $1\, \mu\text{s}$ is $\frac{x}{100}\, \text{mA}$. Then $x$ is equal to ...... . (Take $e^{-1} = 0.37$)

The time constant of an $LR$ circuit is $10 \, s$. When a resistance of $10 \, \Omega$ is connected in series with the existing circuit,the time constant becomes $2 \, s$. The self-inductance of the circuit is ..... $H$.

The current growth in two $L-R$ circuits $(b)$ and $(c)$ is shown in figure $(a)$. Let $L_1, L_2, R_1$ and $R_2$ be the corresponding values in the two circuits. Then:

An inductor coil stores $U$ energy when $I$ current is passed through it and dissipates energy at the rate of $P$. The time constant of the circuit,when this coil is connected across a battery of zero internal resistance,is

The time constant of an $LR$ circuit represents the time in which the current in the circuit