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Transformer

A transformer is a static device consisting of a winding, or two or more coupled windings, with or without a magnetic core, for inducing mutual coupling between circuits. Transformers are exclusively used in electric power systems to transfer power by electromagnetic induction between circuits at the same frequency, usually with changed values of voltage and current. There are numerous types of transformers used in various applications including audio, radio, instrument, and power.

Working principle

A transformer is a static piece of apparatus by means of which electric power in one circuit is transformed into electric power of the same frequency in another circuit. It can raise or lower the voltage in a circuit but with a corresponding decrease or increase in current .The physical basis of a transformer is mutual induction between two circuits linked by a common magnetic flux. In its simplest form of consists of two inductive coils which are electrically separated but magnetically linked through a path of low reluctance.

Fig: Transformer primary and secondary windings
The two coils connected to a source of alternating voltage an alternating flux is set up in the laminated core, most of which is linked with the coil in which if produces mutually induced e.m.f. If the second coil circuit is closed, a current flows in it and so electric energy is transformed from the first coil to the second coil. The first coil, in which electric energy is fed from the a.c. supply mains, it called primary winding and other form which energy is drawn out, is called secondary winding. 
In brief, a transformer is a device that
  • Transformer electric power from one circuit to another
  • It does so without a change of frequency
  • It accomplishes this by electromagnetic induction
  • Where the two electric circuits are in mutual inductive influence of each other