The magnitude of the induced emf in a coil of inductance $30 \ mH$ in which the current changes from $6 \ A$ to $2 \ A$ in $2 \ s$ is: (in $V$)

When a current $i$ through a solenoid is increasing at a constant rate, then the induced current is

The inductance of a coil is $60\,\mu H$. $A$ current in this coil increases from $1.0\,A$ to $1.5\,A$ in $0.1\,s$. The magnitude of the induced $e.m.f.$ is

$A$ long solenoid of $N$ turns has a self-inductance $L$ and area of cross-section $A$. When a current $i$ flows through the solenoid,the magnetic field inside it has magnitude $B$. The current $i$ is equal to:

When current in a coil changes from $5\,A$ to $2\,A$ in $0.1\,s,$ an average voltage of $50\,V$ is produced. The self-inductance of the coil is.......$H$.

When the number of turns in a coil is made $3$ times without any change in the length of the coil,its self-inductance becomes