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Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Anyone have any clue as to why the ground electrode in a flyback arc gets much hotter than the one at potential? I would think the one at +HV would get much hotter due to electrons bombarding it, but no...
It is + HV too, both my kilovoltmeter and a neon lamp said so.
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
Charges flow in the arc. But what moves is ions. Which way the charges move depends on the polarity of the current. The current is the same in the ground wire as the hot wire. The temperature depends on the mass of the conductor and the resistance of the coupling between the metalic state and the plasma. Unless you strike the arc in a vacuum, do you think any free electrons will get far? Welding technology would be a good place to seek answers, or even arc light designs have diffences between + and - terminals. Do Faraday's laws of electrolysis apply to current flowing in DC plasmas? Do charges flow at the same rate as ions? What is heavier, cations or anions.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Radiotech, electrons generally travel a lot faster than ions in plasma, do to the considerable difference in mass. They are both subjected to the same electrostatic force, assuming the ion is +1 charge.
You don't actually get much ion flow as such in an arc, compared to electron flow, though (unless you are welding). You will get ions in the plasma as electrons ionise the air molecules. The heat is generated by the electrons essentially losing kinetic energy when they enter the positive electrode.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
A modern LOPT ("flyback") has two high voltage outputs, one of typically 1.2kV which supplies a positive charge to the focusing anode though which the electron beam must travel, and the EHT output which typically provides 20 - 30kV both to the accelerating anode, and to the conductive internal coating of the tube - often aquadag - whose job is to to reduce picture distortion by catching the secondary emission electrons released from the screen by the impact of the electron beam.
The reason that these CRT electrodes are always positively charged, is because the electrons they attract and control are negative.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Yeah I knew flybacks put out +HV, but this still doesn't answer the question.
If electron bombardment doesn't heat the ground wire, what does? The difference in heating is quite substantial too. Iron nails melt when they are connected to ground, but the high voltage wire doesn't even get hot...
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