Leyden Jars increase spark length?

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Discussion Overview

The discussion revolves around the use of Leyden Jars in series with Van de Graaff generators and their effect on spark length. Participants explore the relationship between voltage, current, and the role of Leyden Jars as capacitors in this context, questioning the underlying principles and safety concerns associated with these setups.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question why Leyden Jars, treated as capacitors, seem to increase spark length despite the understanding that spark gap size is determined by voltage.
  • Concerns are raised about the safety of using Leyden Jars with Van de Graaff machines, with warnings about the potential danger involved.
  • One participant suggests that the capacitor can supply more current than the generator, which may influence the spark characteristics.
  • Another participant argues that the sparking voltage should remain the same, implying that the addition of Leyden Jars should not affect spark length.
  • Some participants believe that drawing more than a tiny current from the generator causes a significant voltage drop, which could affect performance.
  • Questions are posed about how connecting a Leyden Jar in parallel might reduce leakage from the generator, with some skepticism expressed about this effect.
  • Disagreement exists regarding the observation of increased spark length in videos, with some participants noting personal experience that contradicts the visual evidence.

Areas of Agreement / Disagreement

Participants express differing views on the effects of Leyden Jars on spark length and the underlying electrical principles. There is no consensus on whether the addition of Leyden Jars definitively increases spark length or how they interact with the generator's performance.

Contextual Notes

Participants acknowledge various factors that could influence the performance of the Van de Graaff generator and Leyden Jar setup, such as leakage current, humidity, and the specific characteristics of the machines used in demonstrations.

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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?
 
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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.
 
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tech99 said:
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.
Definitely a "don't try this at home kids" type of thing! [emoji23]
 
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The capacitor can supply more current than the generator.
 
David Lewis said:
The capacitor can supply more current than the generator.
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.
 
I believe when you draw more than a tiny current out of the generator, voltage drops significantly.
 
David Lewis said:
I believe when you draw more than a tiny current out of the generator, voltage drops significantly.
I agree with that, but assuming there is some leakage from the dome, how does connection of a Leyden Jar in parallel reduce leakage?
 
I can't see how the videos show that the spark length is increased.
 
Dadface said:
I can't see how the videos show that the spark length is increased.
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.
 
  • #10
tech99 said:
...how does connection of a Leyden Jar in parallel reduce leakage?
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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