An average induced $e.m.f.$ of $1\,V$ appears in a coil when the current in it is changed from $10\,A$ in one direction to $10\,A$ in the opposite direction in $0.5\,s$. The self-inductance of the coil is.....$mH$.

The length of a solenoid is $\ell$,whose windings are made of a material of density $D$ and resistivity $\rho$. The winding resistance is $R$. The inductance of the solenoid is (where $m$ = mass of winding wire,$\mu_{0}$ = permeability of free space).

The coefficient of self-inductance of a solenoid is $0.18\, mH$. If a core of soft iron of relative permeability $900$ is inserted,then the coefficient of self-inductance will become nearly.....$mH$.

$A$ $12\,V$ battery connected to a coil of resistance $6\,\Omega$ through a switch,drives a constant current in the circuit. The switch is opened in $1\,ms$. The emf induced across the coil is $20\,V$. The inductance of the coil is ........... $mH$.

In a coil,current falls from $5\, A$ to $0\, A$ in $0.2\, s$. If an average $emf$ of $150\, V$ is induced,then the self-inductance of the coil is.....$H$

Calculate the self-inductance of a very long solenoid.