You may think that electricity is pretty standard but its voltage and frequency varies between countries and regions in a single country. Essentially, electrical transformers are used to change the voltage of electricity so that it is suitable for different appliances and locations.
WHERE ARE TRANSFORMERS USED?
You might see electrical transformers at the top of power poles or in electrical appliances. Electrical transformers can be as small as a fingernail and used in items like microphones, or they can be huge and heavy devices that are used in power grids. Power grids have very high voltage so that the electricity can travel long distances but this must be reduced in order for the electricity to be used in our homes. The voltage is stepped down through the transformer and then put into local wires at a substation where it may be stepped down again and again so we can use it.
As an example, the power from the grid may have a voltage as high as 765,000 volts, which is stepped down to 7,200 volts through a substation. Then a local power pole transformer may drop the voltage further to 220-240 volts before it is sent to your home. Larger appliances like water heaters and air conditioners may use this 220-240 volt electricity but others like computers and TVs may need it even lower at 110-120 volts.
HOW DO THEY WORK?
Transformers usually have two coils of wire in them and one has more coils than the other. When electricity in one of the windings transfers to a coil with less windings, then the electricity steps down. And if the electricity in the coil with less turns in the wire is transferred to a coil with more turns in the wire, the voltage steps up. One coil is connected to an input circuit and the other is connected to the output circuit.
However, there is also a type of transformer known as an autotransformer which has only one coil. Both circuits are connected to it at different points so that one circuit has more of the coil and more turns in the wire than the other. These autotransformers are often preferred because they are lighter, smaller, and have better overload tolerance and voltage stability.