transformer 1. A device using electromagnetic induction
to transfer electrical energy from one circuit
to another (i.e., without direct connection
between them). In its simplest form, a transformer
consists of separate primary and secondary
coils wound on a common core of
ferromagnetic material, such as iron. When an alternating
current flows through the primary coil,
the resulting magnetic flux in the core induces an
alternating voltage across the secondary coil; the
induced voltage can cause a current to flow in an
external circuit. Also see AIR-CORE TRANSFORMER,
INDUCTION, INDUCTIVE COUPLING,
IRON-CORE TRANSFORMER, and TURNS RATIO.
2. A section of radio-frequency (RF) transmission
line used to match impedances.
Also see
LINEAR TRANSFORMER.