This month is National Static Electricity Month (At least in Sylmar, anyway). I am using my six foot tall Van de Graaff generator to shock F-16 canopies in order to prove that they can withstand and safely drain away static built up in flight. Bad canopies shock ground crew and pilots. One pilot was badly shocked by his canopy during flight. The current grounded through the wrist strap that holds his hand on the control stick paralyzing his wrist for a few seconds. F-16 pilots consider this to be a bad thing.
A Van de Graaff generator uses a non-conducting belt to carry static to the inside of a metal globe. They are popular items for science teachers. My generator on a good day will throw three foot sparks. The continuous current carried by the belt is only about .00005 amps. A 12 volt car battery will give ten or twenty. But my globe stacks it up where it has no place to go, so the voltage gets into the hundreds of thousands of volts. If you think static generating carpets are annoying, try working with a six foot Van de Graaff generator. Just standing in the same room you pick up charges that remind you electricity is not your friend. But enough tech talk, you want to here what strange things it does.
My strangest demonstration is to throw a tiny scrap of tinfoil into the air near the globe. The tinfoil dances in air around the globe. It flutters around, now touching the globe, now orbiting a few inches away. But now I am working on a new trick. Not as sciencey, but more daring.
Some days (depending on humidity and dust conditions) the generator likes to spark, other days it tends to generate coronas, a.k.a. St. Elmo's Fire. If I slowly move a grounding rod near the globe it will usually generate a corona before it sparks. If the generator is adjusted right then the corona drains as much current as the belt replaces, and no spark happens. I happened to know from experience that direct sparks from the globe are unpleasant, to say the least. [*Z*A*P*] Last week I worked up the nerve to test the corona more personally.
It was a good corona day. My handy dandy grounding rod was making corona easily enough. ZZZzzzzzzzzzz [corona noise.] So I slowly moved the back of my hand up to the globe. It is just like feeling for static on a computer monitor. Try it now. The difference is, you felt static from a quarter inch away, and I felt it from thirty inches away. When I felt the static I slowly extended my finger. ZZZzzzzzzz. It worked just like it should. I could see and feel the corona on my fingertips, and it did not hurt in the slightest. I was holding on to the grounding rod at the same time so I would not pick up a strong charge. It was beautiful. I could do this finger. ZZzzzzz. I could do that finger. ZZzzzzz. It was enough to make you forget that electricity is not your friend.
A while later I was putting the generator away after running a test. I gave it one more try, but in my overconfidence I did not check the conditions or move slowly enough. I reached out with my finger, and *Z*A*P*! [Jump up and down in annoyance at self] Oh well. I guess it still needs some work.