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Re: Capacitor charge, were is it?
On Thu, 31 Oct 1996, Tesla List wrote:
> >A vacuum diode passes charge when the heated cathode boils electrons off
> >and they are drawn towards the anode. If you turn the filament off, the
> >vacuum diode stops conducting and becomes a vacuum capacitor.
> >
>
> Makes sense to me. But the vacuum is still a conductor of electrons when
> the electrons are freed from the cathode.
To preface this, I'm not a physicist, and so I'm probably as confused as you
are, but...
Yes, electrons travel through a vacuum, but not in the conventional sense
of conduction of electricity through matter. The way I understand it, the
conduction of electricity through matter is more of a field phenomenon
where electrons actually move at a very small fraction of the speed of
what we consider to be "current. The individual electrons only make short
jumps between atoms, but the disturbance that one electron has on the next
travels from one end of the wire to the next at nearly the speed of light
Sort of like a crowded highway at rush hour...a disturbance at one end of
the line of traffic can propagate back through the line of cars much
faster than the cars can actually move.
Conductors pass the electrons on easily between atoms, insulators hold
onto their electrons and don't let them go as easily. The better the
insulator, the stronger the hold on the electrons. Vacuum has nothing to
retard the electrons. Once the electron breaks free, it's free to go,
governed only by it's initial momentum and the surrounding electric and
magnetic fields.
So in a sense, it seems like once an electron breaks away from a conductor
into the vacuum, a perfect vacuum could actually be considered a perfect
conductor. I guess what makes a vacuum an "insulator" is the fact that the
only way the electrons get launched into it is by outright emission from
the surface, which is a function of the applied voltage, the work function
of the electrode, the temperature of the surface, etc... and is in NO way
related to the properties of the vacuum itself? Help, Mr. Wizard!
Steve (looking for support) Roys.