Explain in detail about the Transformer with Definition, Types, Principle, Construction, Working and Uses.

Explain in detail about the Transformer with definition, types, principle, construction, working and uses.
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Definitions: A transformer is an electric device which is used for changing the a.c. voltages.
A transformer which increases the a.c. voltages is called a step-up transformer. A transformer which decreases the a.c. voltages is called a step-down transformer.
Principle: A transformer is based on the principle of mutual induction, i.e. whenever the amount of magnetic flux linked with the coil changes, an emf is induced in the neighbouring coil.
Construction: The transformer consists of two coils of insulated wire wound onto a laminated soft-iron frame. The two coils may be wound on top of one another or on opposite sides of the frame.
Working: An alternating current is passed through the primary coil and this sets up a varying magnetic field which cuts the secondary coil. By electromagnetic induction, an EMF is induced into the secondary circuit.
Step-up transformer: In this, the number of turns in the primary coil is less than that in the secondary coil. The primary coil is made up of thick insulated copper wire, with less number of turns, while the secondary coil is made up of thin insulated copper wire, with large number of turns. It converts a low voltage at high current into high voltage at low current. 
Step-down transformer: In this, the number of turns in the primary coil is more than that in the secondary coil. The primary coil is made up of thin insulated copper wire with larger number of turns, while the secondary coil is made up of thick copper wire with less number of turns. It converts a high voltage at low current into low voltage at high current.
Types of Transformers
1. Static transformer: It has been described above.
2. Variable transformer: This consists of a primary and a secondary coil and is made so that one of them can be altered in length. The primary coil has a number of tappings and a movable contact can be placed on any one of these by turning a knobs. There is a step up voltage in the secondary coil. In this way, a very crude control of voltage is obtained.
3. The autotransformer: It consists of a single coil of wire with four contact points coming from it. It works on the principles of electromagnetic induction, but it has the disadvantage that it allows only a small step up and does not render the current earth free.
Energy Losses in a Transformer
1. Copper loss: It is the energy loss in the form of heat in the copper coils of the transformer. This is due to Joule heating of conducting wires.
2. Iron loss: It is the energy loss in the form of heat in the iron core of the transformer. This is due to formation of eddy currents in iron core. It is minimized by taking laminated cores.
3. Leakage of magnetic flux: It occurs in spite of best insulations. Therefore, rate of change of magnetic flux linked with each turn of S1 S2 is less than the rate of change of magnetic flux linked with each turn of P1 P2.
4. Hysteresis loss: This is the loss of energy due to repeated magnetization and demagnetization of the iron core when a.c. is fed to it.
5. Magnetostriction: That is humming noise of a transformer. Therefore, output power in a transformer is roughly 90% of the input power.
Uses of Transformer
A transformer is used in almost all a.c. operations, e.g.
1. In voltage regulators of TV, refrigerator, computer, air conditioner, etc.
2. In the induction furnaces
3. A step down transformer is used for welding purposes.
4. In the transmission of a.c. over long distances.