Question

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
A. `4.8pixx10^(-4)H`
B. `4.8pixx10^(-5)H`
C. `2.4pixx10^(-4)H`
D. `4.8pixx10^(4)H`

Answer 1

Correct Answer - C
`M=mu_(0)pir_(1)^(2)n_(1)n_(2)l`
`=(mu_(0)AN_(1)N_(2))/(l)`
`=(4pixx10^(-7)xx10^(-4)xx300xx400)/(0.2)`
`=2.4pixx10^(-4)H`