The current in a coil decreases from $1 \, A$ to $0.2 \, A$ in $10 \, s$. Calculate the coefficient of self-inductance if the induced $e.m.f.$ is $0.4 \, V$. (in $, H$)

Write down the formula for the self-inductance of a very long solenoid.

If a coil is open,then its self-inductance $L$ and resistance $R$ become:

$A$ circular coil of radius $R$ has $N$ turns of a wire. The coefficient of self-induction of the coil will be $(\mu_0 = \text{permeability of free space})$

The current in a coil of self-inductance $2.0 \, H$ is increasing according to $I = 2 \sin(t^2) \, A$. The amount of energy spent during the period when current changes from $0$ to $2 \, A$ is ...... $J$.

Two different coils have self-inductance $3L$ and $L$. The current in both the coils is increased at the same constant rate. At a certain instant of time, the power given to the two coils is same. At that time, there was current and voltage induced in the two coils. At the same instant, the ratio of energy stored in the first coil to that in the second coil is