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I Leyden Jars increase spark length?

  1. Oct 22, 2016 #1
    Good Evening/Morning/Afternoon Everyone,

    Question: Why is it that demonstrations of Van de Graff generators use Leyden Jars in series to get bigger sparks? If a spark gap's size determined by voltage, and Leyden jars are simply to be treated as capacitors which wouldn't increase voltage, why does adding a Leyden jar seem to increase spark gap and therefore voltage?

    Examples (the only reason I say "increase spark gap" is because there is no way generators of these sizes could make those sparks otherwise)



    Is there some fundamental concept I'm missing here? or are the Leyden jars just there to...look cool?...maybe?
     
  2. jcsd
  3. Oct 23, 2016 #2
    Still thinking about that one.
    But please note that using a Leyden Jar with a VdG machine is very dangerous. Whereas the basic machine is safe, with a Leyden Jar it can kill.
     
  4. Oct 23, 2016 #3
    Definitely a "don't try this at home kids" type of thing!
     
  5. Oct 24, 2016 #4

    David Lewis

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    The capacitor can supply more current than the generator.
     
  6. Oct 25, 2016 #5
    I agree, but the sparking voltage should be the same, giving the same spark length, because the two capacitors (dome and Leyden jar) are in parallel across the generator.
     
  7. Oct 27, 2016 #6

    David Lewis

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    I believe when you draw more than a tiny current out of the generator, voltage drops significantly.
     
  8. Oct 28, 2016 #7
    I agree with that, but assuming there is some leakage from the dome, how does connection of a Leyden Jar in parallel reduce leakage?
     
  9. Oct 28, 2016 #8
    I can't see how the videos show that the spark length is increased.
     
  10. Oct 28, 2016 #9
    Good point. I just know from experience that a 50mm spark is typical but in the video using a Leyden Jar it looks about 200mm. Maybe you are right and it is just a very good machine.
     
  11. Oct 28, 2016 #10

    David Lewis

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    It doesn't, as far as I know. Some current unavoidably flows to ground, depending on the voltage of the dome and humidity in the air, etc., whether the generator is connected to a Leyden jar or not.
     
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