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# Question: Dielectric breakdown of air

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Hi,

I want to find out if there's any specific equipment to measure the dielectric breakdown of air? Or is there any way to construct something which can do so?

Also, if I wanted to conduct an experiment to measure the dielectirc breakdown of air; what are the dependent and independent variables, and what factors would have to be held constant?

Any help would be much appreciated!

Thanks

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Hi,

I want to find out if there's any specific equipment to measure the dielectric breakdown of air? Or is there any way to construct something which can do so?

Also, if I wanted to conduct an experiment to measure the dielectirc breakdown of air; what are the dependent and independent variables, and what factors would have to be held constant?

Any help would be much appreciated! :)

Thanks

I think that if you hold voltage and pressure and humidity constant and vary the distance between electrodes you can take a measure of the dielectric breakdown of air when a spark jumps. Then change the voltage and repeat. Then start again but vary the humidity. Then the pressure. Then try the variables I have missed. ;)

PS & addendum: Dielectric constant - Wikipedia, the free encyclopedia

Measurement

The relative dielectric constant εr can be measured for static electric fields as follows: first the capacitance of a test capacitor C0 is measured with vacuum between its plates. Then, using the same capacitor and distance between its plates the capacitance Cx with a dielectric between the plates is measured. The relative dielectric constant can be then calculated as

For time-varying electromagnetic fields, the dielectric constant of materials becomes frequency dependent and in general is called permittivity.

list of dielectric constants >> http://www.asiinstr.com/technical/Dielectric%20Constants.htm

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Alright. Thanks a lot! ;)

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Would something like this work?

img528.imageshack.us/img528/6016/untitledfo9.png

Someone suggested that I set up a circuit like that. Would it be able to measure the breakdown accurately?

Thanks

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Would something like this work?

img528.imageshack.us/img528/6016/untitledfo9.png

Someone suggested that I set up a circuit like that. Would it be able to measure the breakdown accurately?

Thanks

I'm not qualified to say if the circuit will work. The 'HT' generator marked on the drawing I take is 'High tension' generator? Off hand I know about just Van de Graff generators, and that will definately give you sparks trhough air. Good luck with the project. :doh:

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... Off hand I know about just Van de Graff generators, and that will definately give you sparks trhough air. Good luck with the project.

Here's an article on Van de Graff generators. >> Van de Graaff generator - Wikipedia, the free encyclopedia

My roomy and I bought a desktop size Van de Graff from a science company for about \$150 US. We played/experimented with it for about 2 weeks and then returned it for our money back less about \$20 for shipping. It came with a book describing quite a few experiments & we drew some arcs through air up to about 8". I think it was rated at 20,000 volts.

I confess that I have no idea how you would take measurements of the type you need, even using a Van de Graff. :moon:

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Would something like this work?

img528.imageshack.us/img528/6016/untitledfo9.png

Someone suggested that I set up a circuit like that. Would it be able to measure the breakdown accurately?

Thanks

Interesting project. I'm not quite sure if it will be very valid if you just attribute your observations to wether you see a spark or not. Use a galvanometer to measure the current that may flow once the breakdown occurs.

In theory, it all should work well with the little addition. The Van-de-Graff generator should do just fine if you replace the -ve plate with an earthed one, in the case with some generators, they already replace the plate with a sphere.

You could standardise stuff by separating the spheres of the generator with something with a much higher resistance and dielectric breakdown potential (glass?). Then connecting the spheres to plates of identical dimensions, kept apart with glass.

Hmm... you'll need to find a voltmeter with very high effectiveness, so that it can measure a large potential, and have a huge resistance. The galvanometer must be sensitive, but it might get damaged if the current flow gets worse then acceptable limits. If you go ahead with these ideas, be sure to estimate the current that's gonna flow with the spark.

Gee, now I wanna do this project.

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