A transformer is an electrical equipment that can convert alternating current into direct current. It is used to step down the voltage of a high-voltage source, such as a power line or generator, to lower voltages that are needed by electrical systems. It also allows converting electrical energy into other forms of energy such as heat and light.

The most common type of transformer is the step-up transformer, which takes low voltage output from a battery or other source and steps it up to higher voltage for use in another system. A step-down transformer is usually used to decrease the voltage from a higher voltage source to a lower level for use in an appliance or circuit.