The current through a choke coil increases from zero to $6 \ A$ in $0.3 \ s$ and an induced $e.m.f.$ of $30 \ V$ is produced. The inductance of the choke coil is ....... $H$.

The magnetic flux through a circuit carrying a current of $2.0\,A$ is $0.8\,Wb$. If the current reduces to $1.5\,A$ in $0.1\,s$,the induced $emf$ is......$V$.

$A$ $10 \; \Omega, 20 \; mH$ coil carrying constant current is connected to a battery of $20 \; V$ through a switch. When the switch is opened, the current becomes zero in $100 \; \mu s$. The average emf induced in the coil is $\dots \; V$.

The current flowing in a coil of self-inductance $0.4 \, mH$ is increased by $250 \, mA$ in $0.1 \, s$. The induced $e.m.f.$ will be:

The momentum in mechanics is expressed as $m \times v$. The analogous expression in electricity is

$A$ graph of magnetic flux $(\phi)$ versus current $(I)$ is shown for four inductors $P, Q, R, S$. The largest value of self-inductance is for inductor: