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[Phys-L] Re: Looking for electricity demo apparatus

Wilson J. Gonzalez-Espada wrote:
Here at Tech we had two 14" handheld "sparkers" (dated 1963) that we
used for electricity demos.

John Denker and Bernard Cleyet rightly pointed out that you don't get
any distance with the x-rays produced in air because of the immediate

So...OK, guys, I'll bite...on what electricity demos do you use the
hand held tesla? ...besides your fingers, that is...and nevermind
what the frat boys use it for.

I know the chemists and glass blowers use them for leak checking
their glass apparatus for cracks, but that is under vacuum, and they
generally don't have it on very long before they find the leak. On
what electricity demos do you use the induction spark coil *in air*?

Now for my *real* stupidity part: John or Bernard: I understand
about the MFP in air. What I don't understand is what happens to the
x-rays produced in x-ray tubes or x-ray apparatus when they leave the
tube and enter air. Are they stopped in a few cm of air and rendered
harmless? What's going on in medical applications, for example? Is
it that the tubes operate at higher than 10 KV and have high enough
energy to travel far enough to penetrate and be stopped in the body?
Is there another mechanism I am overlooking? I am missing some basic
physics, which is probably straight forward to the nuclear
experimentalists. Karl

Dr. Karl I. Trappe, outreach consultant Home (512) 264-1616
Research Scientist Associate V (retired)
Senior Lecturer in Physics (retired)
Physics Department, Mail Stop C-1600
The University of Texas at Austin
Austin, Texas 78712-1081
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