The inductance of a solenoid $0.5 \, m$ long of cross-sectional area $20 \, cm^2$ and with $500$ turns is......$mH$

In a fluorescent lamp choke (a small transformer),$100 \; V$ of reverse voltage is produced when the choke current changes uniformly from $0.25 \; A$ to $0 \; A$ in a duration of $0.025 \; ms$. The self-inductance of the choke (in $mH$) is estimated to be:

$A$ 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:

Current in a circuit falls from $5.0 \ A$ to $0.0 \ A$ in $0.1 \ s$. If an average emf of $100 \ V$ is induced,then the value of self-inductance of the circuit is . . . . . . . (in $H$)

The length of a wire required to make a solenoid of length $l$ and self-induction $L$ is

An air-cored coil has a self-inductance of $0.1 \ H$. $A$ soft iron core of relative permeability $1000$ is introduced,and the number of turns is reduced to $\frac{1}{10}$ of the original. The new value of self-inductance is: