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Electrically charged gas

  1. Feb 16, 2013 #1
    Hello, could you please share some insights on the matters i'm about to ask.

    The examples will be without any numbers of real physical dimensions more like theoretical concepts.

    In a fluorescent lamp or gas discharge lamp the electrons flow from cathode to cathode(anode ??) as I believe they change places 50/60 times a second because the ac current does so either, but that's not of highest importance here , so the electrons flow exciting the gas(mercury vapor)) atoms which give a UV photon emission on the phosphor coating on the walls which in turn radiate em radiation in the visible spectrum at a certain wavelength.
    The questions is while does electrons are traveling in the lamp they not only excite the mercury atoms but create and emf right? Like every moving charge does.So if I would wrap windings of copper around the long tube fluorescent bulb would I see some voltage induced?
    Or in this case most if the electron energy is wasted as visible light rather than other forms of em frequencies?


    The second question would be , imagine a tube like (possibly made of glass) enclosure , then low pressure gas in it and electrodes at both ends of the tube. A dc current source applied to the electrodes making one cathode the other anode depending on the polarity.
    Now assume the voltage is high enough for the gas to conduct, when this happens again the tube has some windings wound in the middle of it would there be induced voltage/current in those windings because of the electron flow perpendicular to them?
     
  2. jcsd
  3. Feb 16, 2013 #2

    mfb

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    As every variable current flow, it generates a variable magnetic field, indeed. So what?
    There are significant non-radiative losses, but a good fraction of the energy gets converted to visible light.
     
  4. Feb 17, 2013 #3
    Ok, then if the fluorescent gas discharge lamp would be powered from dc source , not taking into account the need for limited current and so just the fact a dc power source now the one end become the cathode the other the anode , electrons flow would that electron flow through the tube induce emf in those windings around the tube or in this case it wouldn't ?
    I know that dc has a uniform static magnetic field but I always wondered what happens when that dc is passed along a gas or some other conducting environment ? I guess the same as when it is passed along a wire but still someones approval of my thinking and little explanation would be great.
     
  5. Feb 17, 2013 #4

    mfb

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    That does not matter, you get the same results as with a metallic conductor.
    In this case: No induced voltage.
     
  6. Mar 1, 2013 #5
    Winding a copper wire around the tube will indeed induce a current the wire that is useful enough to charge phone batteries ect. I was in Nigeria a few years ago and saw this regularly done!
     
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