When the current in a coil changes from $8 \; A$ to $2 \; A$ in $3 \times 10^{-2} \; s$,the $e.m.f.$ induced in the coil is $2 \; V$. The self-inductance of the coil (in $mH$) is:

The current in a coil changes from $3 \,A$ to $1 \,A$ in $0.1 \,s$ in a coil of self-inductance $8 \,mH$. The emf induced in the coil is

$A$ circuit having a self-inductance of $1 \text{ H}$ carries a current of $1 \text{ A}$. To prevent sparking when the circuit is broken,a capacitor which can withstand $500 \text{ V}$ is connected across the switch. What is the minimum value of the capacitance of the capacitor (in $\mu \text{ F}$)?

When the current through an inductor is changed from $2 \,A$ to $6 \,A$ in time $2 \,s$, the emf induced in it is $3 \,V$. Then the inductance of the inductor is (in $\,H$)

$A$ solenoid is connected to a battery so that a steady current flows through it. If an iron core is inserted into the solenoid, will the current increase or decrease? Explain.

The self-inductance of a long solenoid of cross-sectional area $A$,length $l$ and $n$ turns per unit length is given by