The self-inductance of a coil is $L$. Keeping the length and area the same,the number of turns in the coil is increased to four times. The self-inductance of the coil will now be

$A$ toroid is a long coil of wire ($N$ turns) wound over a circular core. The coefficient of self-induction of the toroid is [The magnetic field in it is uniform and $R >> r$,where $r=$ radius of wire,$R=$ radius of coil] ($\mu_0=$ permeability of free space).

Which of the following is not a unit of inductance?

$A$ coil is wound on a core of rectangular cross-section. If all the linear dimensions of the core are increased by a factor of $3$ and the number of turns per unit length of the coil remains the same,the self-inductance increases by a factor of:

The self-inductance $(L)$ produced by a solenoid of length '$l$' having '$N$' number of turns and cross-sectional area '$A$' is given by the formula (where $\phi$ = magnetic flux,$\mu_0$ = permeability of vacuum).

$A$ coil is wound as a transformer of rectangular cross-section. If all the linear dimensions of the transformer are increased by a factor of $2$ and the number of turns per unit length of the coil remains the same,the self-inductance increases by a factor of: