In electronics, a valve is a device consisting of two or more metal plates enclosed in an evacuated glass bulb. One of the metal plates is heated, causing electrons to be emitted. If a positive charge is applied to the other plate, the electrons will move towards it and the valve will conduct electricity. Valves have largely been superseded by transistors which are smaller.


Opens to allow air into or exhaust out of the engine and close to seal the combustion pressure within the chamber.

Mechanical Engineering

Numerous mechanical devices by which the flow of liquid, gas, or loose material, in bulk may be stopped, started, or regulated by a moveable part that opens, shuts, or partially obstructs one or more passageways.

See also: Acorn Valve, Ball Valve, Buncher Grid, Butterfly Valve, Differential Pressure Valve, Flow Control Valve, Heptode, Modulating Valve, Needle Valve, Pop Valve, Pressure Relief Valve, Thermostatic Valve, Triode, Two Position Valve, Two-Way Valve.

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Subjects: Electronics Engines Mechanical Engineering

Valtorc International A major supplier in the industrial control and actuated valves market worldwide supplying ARRA CERTIFIED Ball Valves, Butterfly Valves, V-Port Ball Valves and many more American made products since 1980.