If $N$ is the number of turns in a circular coil,the value of its self-inductance varies as:

When the number of turns in a coil is doubled without any change in the length of the coil,its self-inductance becomes

Two different coils have self-inductance $3L$ and $L$. The current in both the coils is increased at the same constant rate. At a certain instant of time, the power given to the two coils is same. At that time, there was current and voltage induced in the two coils. At the same instant, the ratio of energy stored in the first coil to that in the second coil is

$A$ solenoid has a length of $1 \,m$ and a cross-sectional area of $0.02 \,m^2$. If the number of turns in the solenoid is $5000$, then the self-inductance of the solenoid is: (in $\pi \,H$)

The current through an inductor is given by $i = (10 + 20t) \, A$,where $t$ is in $s$. The induced $emf$ in the inductor is $4 \, V$. The total flux linked with the inductor at $t = 2 \, s$ is ...... $Wb$.

Consider a solenoid carrying current supplied by a $DC$ source with a constant $emf$ containing an iron core inside it. When the core is pulled out of the solenoid,the change in current will: