An infinite long straight conducting cylinderical shell of radius a is surrounded by a thin coaxial infinite conducing cylinderical shell of radius `b`. Assuming current flows uniformly through the cylinderical shell returns through the outer shell, the inductance per unit length for this arrangement is

Options

A. `(2mu_0)/(pi) 1n(b/a)`
B. `(mu_0)/(pi)1n(b/a)`
C. `(mu_0)/(2pi)1n(b/a)`
D. `(mu_0)/(4pi)1n(b/a)`

Answer

C

Explanation

`int_a^b(mu_0i)/(2pix)dx=(mu_0i)/(2pi)log (b/a), L=(mu_0)/(2pi)log(b/a)`