Transformers:
A device used to transfer the energy using inductive coupling of wires between two cores. The varying current in the primary winding induces emf in the secondary winding through a varying magnetic flux in the core.

The transformer works on Faraday's law. When an electric current passes through a long coil of wire, then there will be a strong magnetic field inside the coil and weak in the outer the coil. The lines of the magnetic field would run through the coil which would spread out from one end, and go round the outside.

The current in the secondary coil is produced due to its own magnetic flux, which would be opposite to that of primary coil. If the current in the secondary coil increases by increasing the load, then the flux in the core gets reduced. Hence, the back e.m.f. in the primary coil therefore falls and the current in the primary increases. Eventually the situation will stabilize.

Ideal transformers will have no losses in its flux or energy, whereas there would be some energy loss in the real transformers:

1. Heat produced by the coils. This loss of energy as heat can be reduced by using oil.
2. Eddy currents in the core. This can be reduced using laminated core.
3. Hysteresis loss– As the direction of the magnetizing fields change, some of energy would be lost due to heating and realignment of magnetic domains in the core. This can be reduced using soft Iron for the core.

There are two types of transformers: (a) Step up and (b) step down transformers. (a) Step up transformers: A step up transformer is used to convert a low voltage to high voltage. Its secondary voltage is greater than the primary voltage. This kind of transformer “steps up” the voltage applied to it.

(b) Step down transformers: A step down transformer is used to convert a high voltage to low voltage. Its secondary voltage will be less than the primary voltage. This type of transformer “steps down” the voltage applied to it.