A solenoid of lenght 30 cm with 10 turns per centimetre and area of cross-section `40cm^(2)` completely surrounds another co-axial solenoid of same length, area of cross-section `20cm^(2)` with 40 turns per centimetre. The mutual inductance of the system is

Options

A. 10H
B. 8H
C. 3mH
D. 30mH

Answer

C

Explanation

Mutual inductance of the system ,
`M = mu_0 n_1 n_2 A_2 l`
`therefore M = 4pi xx 10^(-7) xx 1000 xx 4000 xx 20 xx 10^(-4) xx 30 xx 10^(-2)`
` = 301.44 xx 10^(-5) H = 3mH`