Inductive coupling

In electrical engineering, two conductors are referred to as mutual-inductively coupled or magnetically coupled when they are configured such that change in current through one wire induces a voltage across the ends of the other wire through electromagnetic induction. The amount of inductive coupling between two conductors is measured by their mutual inductance.

The coupling between two wires can be increased by winding them into coils and placing them close together on a common axis, so the magnetic field of one coil passes through the other coil. The two coils may be physically contained in a single unit, as in the primary and secondary sides of a transformer, or may be separated. Coupling may be intentional or unintentional.

Unintentional coupling is called cross-talk, and is a form of electromagnetic interference. Inductive coupling favors low frequency energy sources. High frequency energy sources generally use capacitive coupling.

An inductively coupled transponder comprises an electronic data carrying device, usually a single microchip, and a large coil that functions as an antenna. Inductively coupled transponders are almost always operated passively.