rectifier, component of an electric circuit used to change alternating current to direct current. Rectifiers are made in various forms, all operating on the principle that current passes through them freely in one direction but only slightly or not at all in the opposite direction. One early type of rectifier was the diode electron tube. Semiconductor rectifiers are essentially diodes made large enough to safely dissipate the heat caused by current flow. For heavy currents, they are often equipped with cooling fins or heat sinks. Rectifiers are commonly used in power supplies for electronics. There are two kinds of mechanical rectifiers. One, for polyphase alternating current, is a rotating switch that is synchronized with the fluctuations of the alternating current. The other uses a synchronized vibrating reed to change single-phase alternating current into pulsating direct current. Both have been largely superseded by solid-state devices.
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