Question

Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon?

Answer 1

The mutual inductance between two coils (say 1 and 2), can be given by,

$M_{12}=N_2\frac{{\varphi }_{21}}{i_1}$

Where,${\varphi }_{21}$is the flux induced in coil 2, due to the change in current ($i_1$) in coil 1,and $N_2$ is the number of turns in coil 2.

1. That means mutual inductance is proportional to the emf induced in coil 2, due to the change in current in coil 1.
2. Note the emf induced in coil 2, depends on the orientation (i.e. placing them face to face helps maximize the induced emf) and position (i.e placing them close to each other will increase the induced emf).

Therefore, the mutual inductance between a pair of coils, when placed close to each other, depends upon the relative position and the orientation of the two coils.