Home > Encyclopedia of Science > Cathode

• Vacuum tubes
• Electrochemical cells
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A cathode is one of the two electrodes used either in a vacuum tube or in an electrochemical cell. An electrode is the part (pole) of a vacuum tube or cell through which electricity moves into or out of the system. The other pole of the system is referred to as the anode.

Vacuum tubes

A vacuum tube is a hollow glass cylinder from which as much air as possible has been removed. In a vacuum tube, the cathode is the negative electrode. It has more electrons on its surface than does the other electrode, the anode. Electrons can accumulate on the surface of a cathode for various reasons. For example, in some vacuum tubes, the cathode is heated to a high temperature to remove electrons from atoms that make...