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Valve little common sense
From;  Author:Stand originally
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One, thermionic blast off

Learn in electrician in, of concerned electric current directional be such: Directional motion of the electron formed electric current, so, this electron from why and come? We know, between electronic theory, have " blast off thermionicly " phenomenon, those who say is, in metallic atom, the electron with card the outerest nucleus is sucked to his as a result of nucleus lead force lesser, have a plenty of what can move between atom, this is the free electron that we say. Although its are OK mobile, the appeal that gets nucleus is lesser also, but still can't leave metallic outside, but we discover at the same time again, when temperature heighten, the athletic rate of these free electron increases, kinetic energy can increase, when its kinetic energy is more than when what needing transgression power, the electron can overcome the gravitation of nucleus and fly from metallic surface, this is " thermionic blast off " phenomenon.


2, the cathode of valve


1, the sort of cathode


Electronic object blasts off to call cathode in valve, the cathode sort of inchoate valve is not much, now the progress as a result of science and technology, the sort of cathode becomes increasing, but wait to still take mainstream place like carbonization cathode, oxide cathode, tungsten cathode.


Tungsten cathode: Just as its name implies, this is the negative electrode that makes with tungsten filament, it needs to control ability to be able to launch more electron in 2300 Celsius, should achieve such temperature energy apparently very much use up very can big, but tungsten is very stable element, its stability is so good, and life is long also, so multi-purpose in high-power transmitting tube.


Carbonization cathode: It is the negative electrode that makes with carbon and oxidation thorium in the apply on tungsten filament, it controls emissive electron in 1700 Celsius about, compare with tungsten cathode photograph, its specific power consumption is low, but stability is inferior to tungsten cathode and cannot work to be pressed in Gao Bing, because this is multi-purpose at medium power transmitting tube.


Oxide cathode: It is the negative electrode that the oxide such as strontium, calcic, barium besmear is on nickel silk and makes, in about 800 Celsius the left and right sides can launch more electron, this kind of cathode relatively before 2 kinds emissive electric current will be a lot of bigger, but have the job again at the same time the not stable, defect that cannot work to ion is pounded and be damaged at Gao Bing pressing, Yi Shouzheng, so multi-purpose be in charge of at receiving message or make small-power valve, have a fever the tube that friend uses also is oxide cathode valve more.


2, cathode of straight hot formula and hot type cathode
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