If a second coil is placed in the field of a coil connected to an AC source, the induced AC voltage in the second coil is known as __________ induction.

The induced AC voltage in a second coil placed in the magnetic field of a coil connected to an AC source is referred to as mutual induction. This phenomenon occurs when a varying current in the primary coil produces a changing magnetic field, which then induces an electromotive force (EMF) in the nearby secondary coil. The mutual induction is crucial in transformer operations, where it allows energy transfer from one coil to another efficiently without direct electrical connections.

The term emphasizes the interaction between two coils, highlighting that the induction in the second coil is a result of the influence of the primary coil's magnetic field. This is fundamental to understanding electromagnetic principles and devices that rely on the coupling of magnetic fields between coils, such as inductors and transformers used in electrical systems.