The $SI$ unit of inductance,the henry,cannot be written as:

$A$ coil has $N$ turns and the current passing through it is $I$ ampere,resulting in a self-inductance of $L$ Henry. If the current changes to $5I$ $A$,the new self-inductance will be . . . . . . $H$.

With the help of $L = \frac{N\phi}{I}$ and $\varepsilon = -L\frac{dI}{dt}$,give two definitions of self-inductance.

$A$ copper wire is wound on a wooden frame,whose shape is that of an equilateral triangle. If the linear dimension of each side of the frame is increased by a factor of $3$,keeping the number of turns of the coil per unit length of the frame the same,then the self-inductance of the coil:

An air-cored solenoid with length $30 \ cm$,area of cross-section $25 \ cm^2$ and number of turns $500$ carries a current of $2.5 \ A$. The current is suddenly switched off for a brief time of $10^{-3} \ s$. How much is the (nearly) average back e.m.f. induced across the ends of the open switch in the circuit (in $V$)? (Ignore the variation of magnetic field near the ends of solenoid)

The self-inductance $L$ of a solenoid of length $\lambda$ and area of cross-section $A$ with a fixed number of turns $N$ increases as