There are two coils A and B separated by some distance. If a current of 2 A flows through A, a magnetic flux of `10^(-2)` Wb passes through B (no current through B). If no current passes through A and a current of 1 A passes through B, what is the flux through A ?

Explanation

Mutual inductance of system of coil A and coil B is ,
`M_21=phi_2/I_1=10^(-2)/2`
`M_21=5xx10^(-3)` H
Now `M_21=M_12=5xx10^(-3)`H , but
`M_12 = phi_1/I_2`
`therefore phi_1=M_12I_2 [ because M_12=M_21]`
`=5xx10^(-3)xx1`
`phi_1=5xx10^(-3)Wb` = 5 mWb