what is mutual inductance

Mutual inductance is a circuit parameter that describes the interaction of one coils magnetic field on another coil as it induces a voltage in the adjacent coil. It is defined as the ratio between the EMF induced in one loop or coil by the rate of change of current in another loop or coil. Mutual inductance is important as the mechanism by which transformers work, but it can also cause unwanted coupling between conductors in a circuit. The coefficient of mutual induction, or mutual inductance, depends only on the geometrical factor of the two coils, such as the number of turns and radii of two coils and on the properties of a material medium, such as the magnetic permeability of the medium surrounding the coils. To find mutual inductance, one can assume current in one of the coils, deduce the expression for the magnetic field in the neighboring coil due to the current, write the flux linkage equation, obtain the magnetic flux linked, compare the above two equations, and find mutual inductance.