21.4. Transformers http://www.ck12.org
(a) Calculate the EMF of the secondary.
(b) If the secondary current is 3.0 A, what is the primary current?
(c) What power is drawn by the primary?- transformer: An electric device consisting essentially of two or more windings wound on the same core,
which by electromagnetic induction transforms electric energy from one circuit to another circuit such that the
frequency of the energy remains unchanged while the voltage and current usually change. - primary coil:A coil to which the input voltage is applied in a transformer.
- secondary coil:The coil in a transformer where the current is induced.
- step-up transformer:A step-up transformer is one that increases voltage.
- step-down transformer:A step-down transformer is one that decreases voltage.
Electrical resistance within a wire is dependent not only on the material of the wire, but on the length of the wire
and the amount of current flowing through it. By converting electrical power to high voltage and low current, power
companies can efficiently transfer energy over great distances with little loss. The power must be converted back at
the destination for use in homes and businesses.
Well-built transformers can function with virtually no loss as the transformation is the result of the expansion and
contraction of fields around a core, no resistor is necessary.