The average $e.m.f.$ induced in a coil in which the current changes from $2 \ A$ to $4 \ A$ in $0.05 \ s$ is $8 \ V.$ What is the self-inductance of the coil in $H$?

$A$ constant current $I$ is maintained in a solenoid. Which of the following quantities will increase if an iron rod is inserted in the solenoid along its axis?
$(a)$ Magnetic field at the centre
$(b)$ Magnetic flux linked with the solenoid
$(c)$ Self-inductance of the solenoid
$(d)$ Rate of Joule heating

If in a coil the rate of change of area is $5 \, m^2/ms$ and the current changes from $2 \, A$ to $1 \, A$ in $2 \times 10^{-3} \, s$. If the magnetic field is $1 \, T$,then the self-inductance of the coil is......$H$

The inductance of a close-packed coil of $400$ turns is $8 \, mH$. $A$ current of $5 \, mA$ is passed through it. The magnetic flux through each turn of the coil is

For a toroid,$N = 500$,radius $R = 40 \text{ cm}$,and area of cross-section $A = 10 \text{ cm}^2$. Find the inductance in $\mu\text{H}$.

Calculate the self-inductance of a very long solenoid.