Question about the internal working of the traditional electron tube
LoopyByteloose
Posts: 12,537
Tubes relied on three main components, an anode, a cathode, and a heater element in a vacumn. Of course there was a screen to act as a valve, but it is not important in this discussion.
Of late, I was reading about physics in general.· It occured to me that the heater may be a misnomer as you really cannot transfer heat in a vacumn.
So what is really going on inside the vacumn tube?· I suspect that the heater is creating infrared frequency photos and that hit the cathode and loosen electrons.
In other words, it has nothing directly to do with 'heat'.· It seems to me that a photoelectric effect was used to get the electrons to move across the gap.
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It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
Of late, I was reading about physics in general.· It occured to me that the heater may be a misnomer as you really cannot transfer heat in a vacumn.
So what is really going on inside the vacumn tube?· I suspect that the heater is creating infrared frequency photos and that hit the cathode and loosen electrons.
In other words, it has nothing directly to do with 'heat'.· It seems to me that a photoelectric effect was used to get the electrons to move across the gap.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
Comments
Are you saying the Sun's heat won't travel through the vacuum of space to reach the Earth and make life possible?
What physics book did you read anyway?
In the typical vacuum tube, the heater is part of the cathode. It doesn't heat by radiative transfer but uses direct conduction into the emiting surface, so no photons are involved. The material on the surface of the cathode is designed to emit electrons when heated. The potential between the cathode and the anode then causes the eletrons to "flow" from the cathode to the anode.
I wasn't questioning the Edison Effect at play here, I was wondering where Kramer got the idea thermal infrared light won't travel through a vacuum.
That reminds me of the time i was working on a circuit with a vacuum tube ignitron controlling motor speed of a newspaper press magine. The ignitron was pulling 800 amps at 1200 volts and boy was I nervous. You should have seen the pretty colors dancing around inside the ignitron. What a light show!
The "B" [noparse][[/noparse]B+] battery was for the anode (your high voltage pile.)
Whether direct or indirect, the electrons are "boiled off" of the cathode.
I stand corrected, I do remember those tubes for battery operated devices.
I'm suprised there was no comment about the ignitron tube. They don't have a heater at all. A small cat whisker is touching a pool of mercury on the cathode. Some ignitrons cathode is the pool of mercury. When voltage is applied to the ignitor (cat whisker) mercury electrons are liberated which starts an arc between the cathode to the anode. A very high powered rectifier.
Just looking at one made the hair stand up on the back of my head. I got the impression the tubes going to explode any minute now.
Thermonic emission seems to be the text book answer. But the word itself was likely invented without quantum physics in mind. Does the sun's heat simple come across a vacumn without photons as the carrier, or are photon's colliding with mass of earth [noparse][[/noparse]including the atmosphere] and creating a transfer of heat. That is what I am trying to sort out.
In my experience, most tube filaments are isolated electrically from the other elements. I have an RCA tube manual here for reference. There may be an occasional exception.
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It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
The attached is from "Handbook for Electronics Engineering Technicians", Kaufman & Seidman, McGraw-Hill Book Co., 1976, pg. 18-11.
The heat balance of an object is the sum of energy entering and leaving, by radiation, conduction and convection, plus whatever internal sources there are.
The same is true in a vacuum tube with the heater separate from the cathode in a vacuum. The heat transfer is by radiation (of photons from the heater). The cathode itself reaches a uniform temperature within itself by conduction. The electrons in the phosphor coating on the cathode require only a low energy to break away and break out from the surface, where they drift in the electric field toward the (+) plate. In a power tube, the cathode and plate can also become hot due to power dissipation.
Like the direct sunlight or a radiant heater.
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Tracy Allen
www.emesystems.com
(see attached)
Post Edit -- "The Materials and Shapes of Vacuum Tube Heaters"
http://www.thevalvepage.com/valvetek/heater/heater.htm
090808 -- Indirectly-heated cathodes are electrically-isolated but mechanically-coupled to their heaters with a thermally-conductive ceramic (beryllium oxide, aluminum oxide).
Post Edited (PJ Allen) : 9/8/2008 11:28:36 PM GMT