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Re: [Phys-l] x-ray machine



Hi,

An electron gun is not Ohmic. The number of electrons per second depends on the filament temperature and the extraction potential.
Only after this do the electrons "feel" the main accelerating voltage. Changing this potential by an order of magnitude will do little to change the number of electrons per second.

Thanks
Roger Haar
Physics - UA of AZ

Anthony Lapinski wrote:
I saw a new dentist a few weeks ago. I could easily see the x-ray from the
chair, and wrote down some information. I often use "real"
devices/appliances in my classes when discussing electricity, Ohm's Law,
etc.

x-ray machine:
60 kV
7 mA

Using Ohm's Law, we get:

R = (60,000 V)/(0.007 A) = 8.57 x 106 ohms

I thought this result was interesting -- either very high or Ohm's Law
does not apply well in this case. Any ideas?

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