Tom's question about the "influence machine", posted yesterday, prompted me
to go to the library and to look for a better answer than an improvised guess.
In the "Collected Papers of Lord Rutherford" I see how "a long insulated wire,
15 m long, suspended outside the laboratory window" was "charged by means of
a Wimshurst machine driven by a motor". The wire potential was -26,000 volts
and it was normally exposed for about 30 min. The radioactivity collected was
shown to decay (to background level) in three hours. The paper was published
in 1902; Rutherford was at McGill University at that time.
This reminds me a thread we had two years ago. If you were not a phys-L-er
at that time try the following. Go to a screen of your TV (after it was on
for an hour or so, or to your computer screen, and wipe its dirt with a wet
tissue paper. Then put the dirt in front of your GM tube and count for
about 5 minutes. Most likely you will observe at least two or three times
more counts than without the tissue. The dominant half-life, if I recall
correctly was something like 40 minutes. Then a tail with T=10 hrs or so.
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: Gedanken-ing is not enough; physics is an experimental science! :
: Inspired by thinking about phys-L messages on capacitors :
: Ludwik Kowalski :
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kowalskiL@alpha.montclair.edu http://www.csam.montclair.edu/~kowalski