The mutual inductance `M_(12)` of coil 1 with respect to coil 2

Options

A. Increases when they are brought nearer
B. Depends on the current passing through the coils
C. Increases when one of them is rotated about an axis
D. Is the smae as `M_21` of coils 2 with respect to coil 1

Answer

A,D

Explanation

The mutual inductance `M_2` of coil increases when they are brought nearar and is the same as `M_2` of coil `2` with respect to coil 1.
`M_12`i.e., mutual inductance of solenoid `S_1`with respect to scolenoid `S_2` given by `M_21=mu_(0)n_(1)n_(2)pir_(1)^2l`

where signs are as usual.
Also, `M_12` i.e., mutual inductance of solenoid `S_2` with respect to scolenoid `S_1`is givne by `M_21=mu_0n_1n_2pir_(1)^(2)l`
So, we have `M_12=M_21=M`