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. 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.