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Corona Discharge is either a cool effect or the bane of your existence depending on your point of view. Corona, in this respect, means the dimly fluoresceing gasses that are produced when electric charge leaks off of a high voltage source into the air.

My personal experience with Corona Discharge is when I was repairing a Van de Graaff generator at the Exploratorium. This particular generator got up to about 60,000 volts, which is quite exciting. However, this was a haggard and old piece of technology, and the sphere was damaged, scratched, and misshapen. All the points created by these injuries to the sphere provided metaphorical 'jumping off points' for the electrons to leak out into the atmosphere, instead of staying on the sphere.

So, in my case, it was a bane. That leakage prevented the generator from generating even higher voltages, by letting electrons leave the sphere.

Though, it can be cool! We (by we I mean a cool volunteer in the machine shop) built a Corona Motor, which is a rocket motor with no moving parts, and no fuel. It consists of the motor bar, and the stand. The motor bar is like an S that only has two 90 degree bends in it, and the end bits after the bends are sharpened. The stand has a coil that rests on the sphere, and has a point that rests in a hollow drilled out in the exact center of mass of the motor bar.

When this assembly is placed on top of a Van de Graaff generator's sphere, and let to charge up to 30,000 Volts or so, the escaping electrons will bump into the atoms in the atmosphere, bump some of their electrons up to higher energy levels, and cause them to emit light, but also to expand slightly, and heat up. This causes thrust. The assembly speeds up until it falls off.

If you actually want to see Corona Discharge, you must be in a really, really dark room. Like, a closet with no windows with towels stuffed around the door. And there should be a Van de Graaff generator in there. If you turn it on, in the dark, there'll be purple-blue glowing around where the sphere is losing charge, and if you do the Corona Motor in the dark, you'll see glowing clouds the size of your fingernail swirling around the top of the sphere. Pretty cool stuff!

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