Device in which, by electromagnetic
induction, an alternating current (AC) of one
voltage is transformed to another voltage,
without change of frequency. Transformers are
widely used in electrical apparatus of all
kinds, and in particular in power
transmission where high voltages and low
currents are utilized. A transformer has two
coils, a primary for the input and a
secondary for the output, wound on a common
iron core. The ratio of the primary to the
secondary voltages (and currents) is directly
(and inversely) proportional to the number of
turns in the primary and secondary coils.