The self inductance L of a solenoid of length l and area of cross-section A, with a fixed number of turns N increases as

Options

A. I and A increase.
B. decreases and A increases.
C. I increases and A decreases.
D. both l and A decrease.

Answer

B

Explanation

As we know that,
`L = mu _(r) mu _(0) ( N ^(2) A )/(l)`
As L is constant for a coil,
`L prop A and L prop -`
As `mu _(r)` and N are constant here so, to increase L for a coil, area A must be increased and l must be dereased.