A varying current in a coil change from `10A` to `0A` in `0.5 sec`. If the average emf induced in the coil is `220V`, the self inductance of the coil is

Options

A. 11 H
B. 22 H
C. 5.5 H
D. 5 H

Answer

A

Explanation

Coefficient of self-induction of a coil is numerically equal to the amount of magnetic flux linked with the coil when unit current flows through the coil.
emf induced in the coil is given by
`e=-(dphi)/(dt)=-(d)/(dt)(LI)`
or `e=-L(dI)/(dt)`
or `220=(-L(0-10))/(0.5)=(10L)/(0.5)=20L`
`therefore L=(220)/(20)=11H`