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Shocked by Van de Graaff Generator

  1. May 14, 2007 #1
    Today I got my first accidental shock when I touched a Van de Graaff generator in my physics class after it had been on for a while and after it had built up charge. I wasn't thinking at the time and didn't realize that I should have put my hand on the V.D.G.G. before it turned on so it couldn't build up charge like that and so I wouldn't get the current all at once.)

    The shock hurt at the moment, and maybe for a little while later (like a couple minutes or so) and then after that I just felt really jittery from being nervous and surprised by the shock. I'm not sure what the voltage was on it (there was a scroll setting that I assume adjusted voltage) but it was a V.D.G.G. in my high school AP Physics classroom, for whatever that's worth.

    Anyways, I'm a bit worried that the shock could have harmful effects on me (long-term or short-term). I really don't like the idea of high currents running through me. I'm freaked out by how it can mess up the brain, nervous system, and burn things... like organs... and did I mention mess up the brain?

    Logically I know that this happens all the time to physics students and teachers all over the world. Another physics teacher of mine told me that he asked his doctor the same question, and got the response: "in general, if the shock doesn't get you there and you don't hurt long afterwards, you'll be fine". I also know that the physics teacher who was in the room at the time witnessed my accident and set the voltage beforehand himself (he expected me to put my hand on the generator before it started up), and if there was really something to worry about, he probably would have made sure I was okay. Furthermore, I have heard that Van de Graaff generators have very little amperage.

    Despite this logical argument against the shock harming me in any way, I'd just like a little reassurance that I have nothing to worry about :P Also, is the general rule of thumb "if the shock doesn't get you right there, and you don't hurt long afterwards, you should be fine" trustworthy? Furthermore, can someone confirm that Van de Graaff generators have little amperage despite their high voltage?


    In addition to the above questions, I have an additional theoretical question that this incident has brought to mind. Would the severity of the shock be the same in both of the following cases: (Case 1 is the one that happened to me that's described above; Case 2 is something that a lot of people do in V.D.G.G. experiments).

    Case #1: Turn the Van de Graaff generator on, let it build up charge for a little while, and then touch it and get shocked.
    Case #2: Put your hand on the Van de Graaff generator, becoming an extension of the conductor. Turn the V.D.G.G. on. Touch some ground with your other hand, such as a sink faucet.

    My thinking is that the severity in both of the above cases should be the same, since the voltage is around the same in both cases, and the resistance of your body remains constant. But if there were to be a human chain and it were to happen, then the resistance of the multiple bodies in the chain would lessen the shock.
    Last edited by a moderator: May 14, 2007
  2. jcsd
  3. May 15, 2007 #2


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    1) "Amperage" is not a word. You're looking for the word "current."

    2) Van de Graff generators can only supply current for a very short period of time. It's just static electricity. When you walk across carpet in the wintertime, and touch a doorknob, you get a jolt of some tens of thousands of volts. Current flows for a very brief period of time -- perhaps a few microseconds -- until the charge is equalized. A shock from a doorknob can also make a finger or even an arm a little numb for a while, but causes no permanent damage. Your shock from the generator should similarly have no long-term effect.

    3) The two cases you mention would be identical, if they involve the same difference in potential. If you start grounded, but then touch a generator at 30 kV, you'll get a 30 kV shock. If you start grounded, then slowly build up a 30 kV potential, and then touch something grounded, you'll get a 30 kV shock. Even if the electrons are moving in the opposite direction, it'll feel the same, and have the same physiological consequences.

    - Warren
  4. May 17, 2007 #3
    I think the jitteriness is a direct result of stimulation of the nervous system by the electricity. I could easily be wrong, but I've found that electric shocks (I've had very many) always have this effect on me, whereas other kinds of pain (say, soldering iron burns) don't.

    Your worries about "lasting damage", I'm happy to tell you, are ridiculous. Repeated electroshock therapy directly into people's brains is even used as a medical procedure. And as you point out, some of us get shocked all the freakin' time and there's nothing wrong with us. Us. Us us . Us. :biggrin:

    The body can heal from major things, and a static shock (especially from a VDGG of all things) is a very minor thing. Classroom VDGG's can't really hurt you as far as I know. It's a toy. Really, it's hard to play with one of those and not get shocked. When my elementary school class used to go where they had one of those, we went around shocking each other as a game.
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