What is Coefficient Of Coupling？

The fraction of the magnetic flux generated by the current in one coil that links with the other coil is defined as the coefficient of coupling between the two coils, denoted by k.

Consider two coils, coil A and coil B. When current passes through one coil, it generates magnetic flux. However, not all of this flux will link with the other coupled coil. This is due to leakage flux, and the proportion of the flux that does link is characterized by a factor k, which is known as the coefficient of coupling.

When k = 1, the flux generated by one coil fully links with the other coil, referred to as magnetically tight coupling.When k = 0, the flux from one coil does not link with the other coil at all, meaning the coils are magnetically isolated.

DERIVATION

Consider two magnetic coils, A and B. When current I1 flows through coil A:

The above equation (A) shows the relationship between mutual inductance and self-inductance between the two coils