Mutual inductance
Mutual inductance is a property of two or more coils of wire that are placed in close proximity to each other. It is a measure of how much voltage is induced in one coil due to the changing current in another coil.
When a current flows through one coil, it creates a magnetic field around it. This magnetic field then intersects with the other coil, inducing a voltage in it. The amount of voltage induced depends on the rate of change of current in the first coil and the coupling between the two coils.
The mutual inductance between the two coils is represented by the symbol M and is measured in units of henries (H). It is a positive value when the induced voltage in the second coil opposes the change in current in the first coil (known as the "L" configuration), and a negative value when the induced voltage in the second coil aids the change in current in the first coil (known as the "M" configuration).
Mutual inductance is an important concept in the design and operation of transformers, which rely on the transfer of energy through mutual inductance between primary and secondary coils. It also plays a key role in the functioning of inductive sensors, wireless power transfer systems, and other applications involving electromagnetic coupling between coils.