Date: Fri, 22 Mar 2002 09:28:25 -0800 (PST)

Author: William Beaty

Subject: Re: Safety of Van de Graaff Generators


On Fri, 22 Mar 2002, Karl I. Trappe wrote:

> Warren: This is a good Tap-L topic. My gut response is that if the
> VDG is, itself, safe, then most anything you do with is OK. By
> "safe", I mean if you have a dome *small enough* that the capacitance
> limits the total charge that can be supplied. I confess that I do
> not know a specific number. Perhaps it can be judged by arc length
> of the discharge in air, given that its about 8KV/cm of discharge.

One guy told me his VDG story from years ago. He had a large roll of
mylar drafting film, so he cut it into two lengths, got some rolls of
aluminum foil, and rolled himself a large capacitor. Then he hooked it up
to his VDG machine and let it run. After many hours he realized that he
didn't know how powerful the discharge would be (or whether it was working
at all), so he disconnected it, took it out to his backyard, and stuck it
into the goldfish pond so the charge could leak away.

He said that after the immense BANG, most of the water was missing from
the pond, and all of the fish were dead.

The moral: don't mess with VandeGraaff machines and Leyden jars, to say
nothing of mylar capacitors with hundreds of square feet of plates!

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