The basic idea is to connect the first circuit to a primary winding, typically of many turns of wire in some sort of coil shape which creates a concentrated zone of the high magnetic field on the inside of the coil. Then you want to place a secondary winding (or several) so that as many as possible of the magnetic field lines from the primary go through the secondary as well. This can be done by winding the primary and secondary into the same space, but often a more convenient method is to use a Magnetic core of material with a high magnetic Permeability and low Magnetomotive force. Magnetic field lines like to run in high permeability materials, so you can put the primary and secondary a convenient distance apart and use the core as a conduit to pipe the field lines between them.

Also Read: Induction motor definition and working principles

Then it’s just Faraday’s law twice over. If you apply a fixed voltage to the primary, a steadily increasing current will build up (except for the magnetic effects, a coil is a short circuit), creating an increasing magnetic field, and integrated across the area of the coil, a magnetic flux. According to Faraday’s law, there’s a back voltage generated equal to the rate of change of magnetic flux times the number of turns in the primary. The rate of increase of current will adjust itself until this back voltage is in equilibrium with the applied voltage.

Then, the same increasing magnetic flux is acting on the secondary, so a voltage is induced there as well, except there you multiply by the number of turns in the secondary. If the number of turns in the secondary is different, you have the voltage transforming action for which the transformer is named. More turns in the secondary give a step-up transformer which increases voltage; fewer turns gives a step-down transformer.

Of course, with a fixed input voltage, the poor transformer can’t keep up for more than a very brief time because the current can’t actually keep increasing indefinitely. Sooner rather than later the heating effect of all the current will cause a burnout. So in practice, you only ever use transformers with AC input, where the input voltage reverses regularly and the current never has a chance to build up too much.

Primary winding gets input voltage and produces flux in the iron core, then this settled flux get linked with the secondary winding. Because of ac supply flux will change its direction and magnitude ……so secondary coil will get inducement voltage.

Also Read: Induction motor definition and working principles

Induced voltage=-N(dphi/dt)

Where N is a number of turns in secondary windings and dphi/dt is the rate of change of flux.”-”ve sign describes Lenz’s law.

*As rate of change of flux is same for both,*

E1/N1=E2/N2

**E1/E2=N1/N2………****

**The transformer changes the voltage levels without affecting power.**

Power remains same for both sides.

P1=P2

E1I1=E2I2

E1/E2=I2/I1

**N1/N2=I2/I1(from…**).**

As it is a static device, losses are too small.

**Efficiency: 96℅to98℅**