How is mutual inductance of a pair of coils affected when (i) separation between the coils in increased, (ii) the number of turns of each coil is increased , (iii) a thin iron sheet is placed between the two coils, other factors remaining the same ? Explain your answer in each case.

Explanation

(i) As, `phi = MI`, with the increase in the distance between the coils the magnetic flux linked with the stationary coil decreases and hence the mutual inductance of the two coils will decrease.
(ii) Mutual inductance of two coils can be found out by `M = mu_(0) n_(1) n_(2) AI, i.e., M alpha n_(1) n_(2)`, so with the increase in number of turns mutual inductance increases.