Inductive coupling

The changing magnetic field induces an electromotive force (EMF) voltage in the second wire by Faraday's law of induction.

The two coils may be physically contained in a single unit, as in the primary and secondary windings of a transformer, or may be separated.

An inductively coupled transponder consists of a solid state transceiver chip connected to a large coil that functions as an antenna.

[citation needed] Reducing low-frequency magnetic fields may be necessary when dealing with electronics, as sensitive circuits in close proximity to an instrument with a power transformer may pickup the mains frequency.

Electrical distribution line engineers use inductive coupling to tap power for cameras on towers and at substations that allow remote monitoring of the facilities.

Example of inductive coupling, 1910. The bottom coil is connected to AC power. The alternating magnetic field through the top coil induces current in it which lights the lamp.
k is the coupling coefficient , Le1 and Le2 is the leakage inductance , M1 (M2) is the mutual inductance