Wikipedia:Reference desk/Archives/Science/2018 January 26

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

January 26

Practical implementation of system for electrostatic attraction for pulling and holding large mass

Is it possible to generate enough electrostatic charge to attract a body of 1000kg or higher and specially against gravity what will be the practical implementation a custom Van de graff generator as part of one body or any other practical implemenation because by Coulumbs law this is possible Please give a brief description or rough sketch of such practical system.The two bodies will be oppositely charged of course there may be charge dissipation capacitance dielectric etc. factors or is such a practical system impossible and can such a system be used for energy storage?

comment: Umweltheizung am 26.01.2018 20.01 Uhr This sounds pretty good. Where can I (we) find more Information about that "de graff Generator"?

Van de Graaff generator —107.15.152.93 (talk) 19:53, 26 January 2018 (UTC)

Yes it would be possible. It would not be practical. Think of a million VdG s each lifting 1g of material spread out over a square metre. The total mass lifted would be 1000 kg, the machine would cost 100s of millions of dollars. WAG on energy stored, .05*1000*10=500J, about half a normal 12V car battery. Greglocock (talk) 20:49, 26 January 2018 (UTC)

The idea of lifting a heavy object by electrostatic attraction is appealing. Coulomb's law governs the attraction, so if we were to try to lift a 50 kg (formerly 100 kg) volunteer from the reeducation through labor camp, we want 500 N of force; for a lifting electrode 1 meter away we take ke = 8.99×109 N m2 C−2 over that meter squared times two charges we'll suppose are equal, which means we want 500/sqrt(9x10^9) coulombs on the volunteer and the electrode. which is like 500 x 3.3 x 10^-4 = 1.6 coulombs. The catch is we ought to figure out what kind of voltage we're looking for, and for that we check capacitance, which surprisingly tells us the capacitance of a Van de Graaf generator electrode is 22.24 pF (dang that's precise). Which means for every 22.4 picocoulomb of charge we put on it, we need to increase the potential by a volt, so to get to that 1.6 coulombs we need, I think, a bit less than 10^11 volts. For comparison a little over one megavolt is the maximum power line voltage known to the writers of the Volt article. Arcing of a lightning bolt seems inevitable (Volt says lightning is 100 million volts, but that's all the way from cloud to ground, whereas this is 1 meter!). Note that an electron crossing this voltage would gain much more than the 1.022 MeV needed for pair production ... I'm not sure exactly how or if you can use this to postulate a maximum possible voltage in the situation. There would, in any case, be a few practical difficulties I think. Wnt (talk) 21:59, 26 January 2018 (UTC)

The breakdown voltage of dry air is about 3.4MV / m, so a discharge is inevitable. LongHairedFop (talk) 13:10, 27 January 2018 (UTC)

OP only specified the mass, not the gravity. With arbitrarily low gravity (think of a tiny asteroid) it can be done. However, it won't hold it stably. The body will have a tendency to either fall back to the ground or run into the electrostatic attractor. That in addition to abovementioned arcing problem. PiusImpavidus (talk) 10:56, 27 January 2018 (UTC)