On Dec 3, 2011, at 11:38 AM, Peter Heckert wrote:
Am 03.12.2011 16:20, schrieb Horace Heffner:
I suggest that the dark zone at the tip of the needle is not due
to a vacuum there. It is more likely due to the average delay for
recombination of the ions and electrons. Electron recombination
with ions is likely what produces most of the light.
I believe there is a vacuum for these reasons:
1) I placed a charged needle 1-2 cm above a water surface. The air
blow makes a sharp, mm deep and mm wide hole into the water surface.
If I assume, that the air stream originates from the needle's tip,
wich is measured in µm, the blowing pressure and the repulsion at
the needles tip in a µm distance must be 100 to 1000 times stronger.
The sudden electrostatic acceleration of electrons and ions must
create a vacuum.
This experiment was done with some kV only. I had to turn the
voltage down to avoid sparks, because I had only 1 or 2 cm distance
to the water.
In pressurized air the voltage can be some 100 kV.
2) The electrostatic repulsion is strong enough to drive the
electrons out of the metal.
I believe the force required for this must be many times stronger
than the air pressure.
A side note:
It is interesting that a positive needle blows and also a negative
needle blows.
One should expect that a negative needle would attract the nuclei
and repel the electrons and should suck instead blow.
This does not happen, both needles blow.
So I think, directly at the needles surface, if it is negatively
charged, there should be a vacuum, but not empty, the vacuum must
contain a dense electron cloud.
Peter
You should keep in mind that the ions are replaced with air molecules
at the speed of sound.
The intense field at the tip can deposit electrons on gas molecules
or remove them, depending on tip charge.
BTW, you might enjoy checking the archives for posts by Bill Beaty on
the ability of HV needle tips to generate threads of water molecules
from humidity in the air. Some thread names I recall are "Air
threads" and "Filament ion jets" from 2007.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
