Plate electrode

A plate, usually called anode in Britain, is a type of electrode that forms part of a vacuum tube.

The plate is given a positive potential, and its function is to attract and capture the electrons emitted by the cathode.

In low power tubes it is usually given a black coating, and often has "fins" to help it radiate heat.

In power vacuum tubes used in radio transmitters, it is often made of a refractory metal like molybdenum.

To prevent this most plates in modern tubes are given a chemical coating which reduces secondary emission.

Cutaway diagram of a triode vacuum tube, showing the plate (anode)
The plate from an EL84 pentode tube widely used in audio amplifiers in 1960s era radios and televisions, and still used in guitar amplifiers
Schematic symbol used in circuit diagrams for vacuum tube, showing plate