The current passing through a coil of $120$ turns and inductance $40 \text{ mH}$ is $30 \text{ mA}$. The magnetic flux linked with the coil is:

The dimensional formula of self-inductance is . . . . . . .

$A$ current of $0.5 \ A$ is passed through the winding of a long solenoid having $400$ turns. The magnetic flux linked with each turn is $3 \times 10^{-3} \ Wb$. The self-inductance of the solenoid is: (in $H$)

In a coil,current falls from $5\, A$ to $0\, A$ in $0.2\, s$. If an average $emf$ of $150\, V$ is induced,then the self-inductance of the coil is.....$H$

$A$ long coaxial cable carries current $I$ along its surface. The current flows down the surface of the inner cylinder of radius $a$ and back along the outer cylinder of radius $b$.

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