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

Options

A. `2.4 pi xx 10^(-5)H`
B. `4.8pi xx 10^(-4)H`
C. `4.8pi xx 10^(-5)H`
D. `2.4xx10^(-4)H`

Answer

D

Explanation

`M=(mu_(0)N_(1)N_(2)A)/(l)=(4pi xx 10^(-7)xx300xx400xx100xx10^(-4))/(0.2)`
`=2.4pi xx10^(-4)H`