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Re: FUN: high-speed electrostatic air-threads

On Tue, 16 Jun 1998, Leigh Palmer wrote:

The electrons that leave the tip of the needle don't get very far
on their own, certainly not as far as a millimeter. They interact
with air molecules and do not retain their identities.

Yes, I would think that they would be captured by a Nitrogen molecule and
form a negative ion. But they would retain their identities as charged
particles, its just that the "particle" of e- charge suddenly grabbed a
whole bunch of mass.

In a vacuum
things would be quite different. "Field emission" may not be the
best term to characterize phenomena in air at centimeter distances
from the source.

Would they be so different? True, there would be no long collisionless
trajectories and relativistic speeds. But there still could be an
"electron beam", it would simply need to carry air along with it.

I would expect overall neutrality of the material in the stream. It
is composed of ions of both signs. The electrons (which predominate
the negative ions) are the more mobile, of course. The same thing
happens more dramatically in a lightning bolt. You have a large
current limiting element in your circuit; that's the difference.

When "electric wind" is created by the tip of a charged needle, isn't
there a net electric current? If equal amounts of + and - ions were
emitted, then the current would be zero. If equal and opposite ions were
emitted, then I don't understand why there would be "wind" in the first
place, since I assumed that the wind was the consequence of work done by
the fields as they fling negative air ions away from a negative needle tip
(or positive ions flung from a positive needle.)

OK, now I'm confused. What is the cause of "electric wind" if not a jet
of ions all of the same polarity flowing along a large gradient of
e-field?


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