When the number of turns and the length of the solenoid are doubled keeping the area of cross-section same, the inductance

Options

A. half
B. zero
C. two times
D. four times

Answer

C

Explanation

`L prop(N^(2))/(l)`
`(L_(2))/(L_(1))=((N^(2))/(l))*(l_(1))/(l_(2))`
`=((2n_(1))/(n_(1)))^(2)xx(l_(1))/(2l_(1))=(2)/(1)`
`L_(2)=2L_(1)=2` times