A power transformer is a device that consists of a coil wrapped around an electromagnet that transfers electricity from one circuit to another without changing the frequency of the electric energy. Although the frequency of the electrical energy isn't changed, the voltage and current commonly change when passing through.
The most common types of transformers are the step-up and step-down transformers. The function of a transformer is to maintain a current of electricity by transferring energy between two or more circuits. This is accomplished through a process known as electromagnetic induction. A basic transformer consists of two windings around a shared core. The process of electromagnetic induction, through which electricity reacts to magnetism, transforms electric energy from one set of circuits to another. This allows the frequency of the electrical energy to remain stable and unchanged. Transformers vary widely in size and power, and power grid transformers can weigh hundreds of tons.