cathode
In an electrolytic cell, the negative electrode, towards which positive particles (cations), usually in solution, are attracted. See electrolysis. The cathode is given its negative charge by connecting it to the negative side of an external electrical supply.
In a thermionic valve, cathode ray tube, or similar device, the cathode is the negative electrode, from which electrons are emitted.
In these cases, the flow of electrons is into the device at the cathode. The term is also inconsistently applied in some other cases to electrodes at which the flow of electrons is out of the device – for example, to the negative terminal of a battery.
cathode
In electronics, the part of an electronic device in which electrons are generated. In a thermionic valve, electrons are produced by the heating effect of an applied current; in a photocell, they are produced by the interaction of light and a semiconducting material. The cathode is kept at a negative potential relative to the device's other electrodes (anodes) in order to ensure that the liberated electrons stream away from the cathode and towards the anodes.
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