Editing Plate electrode (section)

{{Short description|Type of electrode used in vacuum tubes}}
[[Image:Triode-english-text.svg|thumb|Cutaway diagram of a triode vacuum tube, showing the plate (anode)]]
[[Image:Roehre anode el84.jpg|thumb|The plate from an [[EL84]] [[pentode]] tube widely used in audio amplifiers in 1960s era radios and televisions, and still used in guitar amplifiers]]  
[[File:Triode schematic labeled.svg|thumb|[[Schematic symbol]] used in [[circuit diagram]]s for vacuum tube, showing plate]]

A '''plate''', usually called '''anode''' in Britain,  is a type of [[electrode]] that forms part of a [[vacuum tube]].<ref>Thomas A. Edison {{US patent|307031}} "Electrical Indicator", Issue date: 1884</ref> It is usually made of sheet metal, connected to a wire which passes through the glass envelope of the tube to a terminal in the base of the tube, where it is connected to the external circuit.  The plate is given a positive [[electric potential|potential]], and its function is to attract and capture the electrons emitted by the [[cathode]].  Although it is sometimes a flat plate, it is more often in the shape of a cylinder or flat open-ended box surrounding the other electrodes.