The magnetic potential energy stored in a certain inductor is $25 \mathrm{mJ},$ when the current in the inductor is $60 \mathrm{mA}.$ This inductor is of inductance 

An inductor of inductance, $L=400 \mathrm{mH}$ and resistors of resistances, $R_1=2 \mathrm{\Omega }$ and $R_2=2 \mathrm{\Omega }$ are connected to a battery of emf $12 \mathrm{V}$ as shown in the figure. The internal resistance of the battery is negligible. The switch $S$ is closed at $t=0$. The potential drop across $L$ as a function of time is,

In the circuit shown below, the key $K$ is closed at $t=0$. The current through the battery is:

In the circuit shown here, the point $C$ is kept connected to point $A$ till the current flowing through the circuit becomes constant. Afterward, suddenly point $C$ is disconnected from point $A$ and connected to point $B$ at time $t=0$. The ratio of the voltage across resistance and the inductor at $t=\frac{L}{R}$ will be equal to,