What is the mutual inductance of a two-loop system as shown with centre separation l

Options

A. `(mu_(0)pia^(4))/(8l^(3))`
B. `(mu_(0)pia^(4))/(4l^(3))`
C. `(mu_(0)pia^(4))/(6l^(3))`
D. `(mu_(0)pia^(4))/(2l^(3))`

Answer

D

Explanation

`B_(1)=mu_(0)/(4pi)*(2M)/l^(3)`

`varphi=B_(1)A_(2)=mu_(0)/(4pi)(2i(pia^(2)))/l^(3)(pia^(2))`
Also, `M=varphi_(2)/i=(mu_(0)pia^(4))/(2l^(3))`