Leyden Jars increase spark length?

[Invictos]

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?

 

[tech99]

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.

 

[Invictos]

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]

 

[David Lewis]

The capacitor can supply more current than the generator.

 

[tech99]

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.

 

[David Lewis]

I believe when you draw more than a tiny current out of the generator, voltage drops significantly.

 

[tech99]

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?

 

[Dadface]

I can't see how the videos show that the spark length is increased.

 

[tech99]

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.

 

[David Lewis]

...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.