Two coaxial solenoids are made by winding thin insulated wire over a pipe of cross-sectional area `A=10 cm^(2)` and length =20cm. If one of the solenoid has 300 turns and the other 400 turns, their mutual indcutance is

Explanation

`M = (mu_(0)N_(1)N_(2)A)/(L)`
`M = (4pi xx 10^(-7) xx 3 xx 10^(2) xx 4 xx 10^(2) xx 10^(-3))/(2 xx 10^(-1))`
`= 2.4 pi xx 10^(-4)H`