A rectifier is an electrical apparatus that converts alternating current, which periodically reverses direction, to direct current, which flows in only one direction. Rectifiers have several uses but are often found serving as components of DC power supplies and high voltage direct current power transmission systems.
Rectification serves many roles other than to generate direct current for use as a source of power. In alternating current, known as AC, the electric charge changes order periodically. Not only current but also the voltage changes because of the change in the current flow. Direct current flows in one direction in case of direct current.