Applying the principle of magnetic induction between coils, an electrical transformer is a device which transforms the voltage from higher to lower. The electric transformer transfigures the alternating current or AC electric energy from one circuit into another with electromagnetic induction.

The transformers are composed of ferromagnetic core and two or more coils labeled as "windings". Any electrical changes in the primary winding create an alternating magnetic field in the core, which multiplies the field and the flux through the secondary windings. This in turn, incites alternating voltage in each of the secondary coils.

If another wire is present near an electric current that is changing strength, the electricity will flow into that wire as magnetism changes. An electrical transformer takes in electricity at a higher voltage and allows it to flow through several coils wound around an iron core.

The magnetism in the core changes as the electric current does. Surrounding the core is an output wire with fewer coils. The electric current within the wire is derived from the fluctuating activity in the magnetism. If the coils are fewer, the voltage is low. This incidence is called "stepped-down" voltage.

Electrical transformers are used in utility poles of electric companies and in changing the voltage in a toy train set. In the household application, when electricity moves from a power plant, it is placed into a high voltage to enable it to travel long distances. The high voltage lines can range between 155,000 to 765,000 volts to have the capacity to travel hundred of miles.

In order to use the electricity in a household or store, it needs to be at a lower voltage. The electricity should be on a "stepped-down" to a lower level using an electrical transformer.

The lower voltage electricity is placed into local electric wires at a substation, which breaks down the larger amount of power into smaller electricity at a lower voltage. Hence, the voltage is stepped-down.

Now, when the smaller transformers take the voltage down to 7,200, the power leaves such substation. The transformer on a utility pole or underground wires transfigures the 7,200 volts into 220-240 volts, which is then sent into your household over three wires.

These three wires go through the electric meter that measures the amount of electricity consumed. Two of the wires are electrical-charged and the other wire serves ground. The Step-up transformer contains greater number of windings on the side where it outputs the energy. It increases the voltage as it reduces the current. It is used in appliances that use 220 volts.

The step-down electrical transformer is used to reverse the winding ratio. Examples of its applications include a battery-run device than can be plugged into the wall, so the radio may run on 12v batteries, and on 110v through adapters having a step-down transformer inside.

Isolation electrical transformers have many applications. They break circuits into primary and secondary. They are also used to prevent capacitance buildup between the primary and secondary which causes high-frequency noise.