When a current in the conducting coil is changed from $5 \ A$ in one direction to $5 \ A$ in the opposite direction in $0.5 \ s$,an average induced e.m.f. in the coil is $2 \ V$. The self-inductance of the coil is (in $mH$)

$A$ 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

$A$ $12\,V$ 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 the circuit shown below,a long time after the key $K$ is closed,the reading in the ammeter is $20 \,mA$. What was the reading (in $mA$) immediately after it was closed?

The self-inductance of a circuit is numerically equal to

The current in self-inductance $L=40\; mH$ is to be increased uniformly from $1\; A$ to $11\; A$ in $4\; ms$. The $e.m.f.$ induced in the inductor during this process is ..... $V$.