A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification, since it "straightens" the direction of current. Physically, rectifiers take a number of forms, including vacuum tube diodes, wet chemical cells, mercury-arc valves, stacks. Before the development of silicon semiconductor rectifiers, vacuum tube and copper oxide- or selenium-based stacks were used. The first vacuum tube diodes designed for recti. Rectifier circuits may be or multi-phase. Most low power rectifiers for domestic equipment are single-phase, but three-phase rectification is very important for industrial applications and for the transmission of e.
