What's Coefficient of Coupling??

The fraction of magnetic flux produced by the current in one coil that links with the other coil is called coefficient of coupling between the two coils. It is denoted by (k).

Two coils are taken coil A and coil B, When current flows through one coil it produces flux; the whole flux may not link with the other coil coupled, and this is because of leakage flux by a fraction (k) known as Coefficient Of Coupling.

When the coefficient of coupling, k is equal to 1, (unity) such that all the lines of flux of one coil cuts all of the turns of the second coil, that is the two coils are tightly coupled together, the resulting mutual inductance will be equal to the geometric mean of the two individual inductances of the coils.

When k=0 when the flux produced by one coil does not link at all with the other coil and thus the coils are said to be magnetically isolated.