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Cathode

From Academic Kids

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Copper_cathode.png
Diagram of a copper cathode

In chemistry a cathode is the electrode of an electrochemical cell at which reduction occurs. It comes (from the Greek word κάθοδος = 'going down'). In an electrolytic cell the cathode is negatively charged and in a galvanic cell the cathode is positively charged. The oppositely charged electrode in that same cell is referred to as the anode.

In physics a cathode is an electrode in a vacuum tube or other vacuum system which produces electrons. Electrons are extracted from metal electrodes either by heating the electrode, causing thermionic emission, or by applying a strong electric field and causing field emission.

Cathodes used for field emission are called cold cathodes. Heated electrodes, frequently called filaments, are much more common. They form the source of the electron beam in cathode ray tubes and the electrodes for fluorescent lamps.

See also

de:Kathode eo:Katodo fr:Cathode it:Catodo nl:Kathode ja:カソード pl:Katoda ru:Катод sl:Katoda sv:Katod

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