Find Van De Graaff charge?

[Albertgauss]

Greetings,

Does anyone know of a way to measure the actual charge of a Van De Graaff generator, in Coloumbs?

One way I thought might be to measure the voltage potential around the generator, and calculate the charge from V = kQ/r, but would this work in just regular air? What obstacles would prevent me from finding V to get Q in regular air, if this method would not work?

Is there any way to control whether a Van De Graaff generator can be charged positive or negative?

 

[berkeman]

Do you have a capacitance meter? If so, can you just measure the capacitance (with the generator off, of course) between the upper conductor and ground? If you know the output voltage, it seems like that should get you close on how much charge is stored when the generator is on... (but I don't know much about VDG generators...)

https://store.schoolspecialty.com/OA_HTML/xxssi_ibeGetWCCImage.jsp?docName=F1635436&Rendition=Large

 

[Albertgauss]

I didn't know they had a capacitance meter. I suppose I should have realized that this technology is made. I can get one. Its going to be a few weeks before I can get one, so this method of determining the charge is going to take awhile, limited by the time it takes to find a capacitance meter.