Re: Magnetic lines like these ?

[brian whatcott <inet@intellisys.net>]

At 08:49 3/2/98 -0800, Bill wrote:
[Ludwik]
> > Vacuum also "conducts" charged particles
> > when an electric field, E, is applied.
>
> I disagree.  Vacuum only conducts when electrons are present, but then
> that is not a vacuum, that is an electron plasma.  A perfect vacuum is a
> perfect conductor.  A hot filament changes the vacuum by adding an
> electron plasma, which is itself a conductor. 
....
> William J. Beaty 

I am uncomfortable with the phrase, "electron plasma."

When Langmuir coined the phrase "plasma oscillation" whence sprang
 the use of the word "plasma", he was observing a highly ionized gas
in a gas-discharge tube, and the idea of a rough parity of electrons 
and ions as a property of the plasma state, persists.
 This is not how one would describe the electron current in a vacuum 
tube, in my view. (The getter was meant to mop up stray ions/atoms 
after all.)

 It's interesting to recall that the oscillation that Langmuir named 
could promote oscillations at 1 GHz which were capable of scattering 
an electron stream more than the gas collision model predicts.

Whatcott