In the circuit shown,the final current through the $30\, \Omega$ resistance when the circuit is completed is ......... $A$.

Switch $S$ is closed at $t = 0$ in the circuit shown. The change in magnetic flux in the inductor $(L = 500 \, mH)$ from $t = 0$ to an instant when it reaches steady state is ...... $Wb$.

$A$ constant voltage of $25 \, V$ is applied to a series $L-R$ circuit at $t=0$ by closing a switch. What is the potential difference across the resistor and the inductor at time $t=0$?

$A$ $50 \, V$ potential difference is suddenly applied to a coil with $L = 5 \times 10^{-3} \, H$ and $R = 180 \, \Omega$. The rate of increase of current after $0.001 \, s$ is ....... $A/s$.

An inductor $(L)$ - resistance $(R)$ battery circuit is switched on at $t = 0$. If the $e.m.f.$ of the battery is $E$,what is the charge passing through the battery in time constant $T$?

When a $DC$ voltage is applied at the two ends of a circuit kept in a closed box, it is observed that the current gradually increases from zero to a certain value and then remains constant. What do you think the circuit contains?