What is the term for when two coils are positioned close enough for their magnetic fields to interact?

The correct term for the interaction of magnetic fields between two coils positioned close enough is mutual inductance. This phenomenon occurs when a change in current in one coil creates a changing magnetic field that induces a voltage in the nearby coil. Mutual inductance is a fundamental principle in electromagnetism, particularly in transformers and various electrical devices where energy transfer between two or more coils is required.

Understanding mutual inductance is crucial in applications such as inductors, transformers, and wireless energy transfer systems, where the efficiency and effectiveness of energy transfer depend on the precise arrangement and interaction of magnetic fields between coils.