Hi Bill,
----- Original Message -----
From: "William Beaty" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Sunday, June 03, 2007 2:55 AM
Subject: Re: [Vo]:ion currents in pingpong balls
> On Sat, 2 Jun 2007, Kyle R. Mcallister wrote:
>
>> About to go on some travels, will get some incense while I am out,
>> preferably something that smells nice and not like a house of ill repute. :)
>
> Y'know, I think incense smoke might give misleading results. Here's a
> weird phenomenon:
>
> Aim a HV needle at a small grounded electrode plate. The electrode
> diameter should be smaller than the distance between the needle and
> electrode. Include a microamp meter in the ground wire to the plate.
>
> Power up the needle. The meter registers significant electric wind
> (significant microamps.)
>
> Now blow your breath across the space between the needle and the plate.
> This should waft the charged air off to the side, and greatly lower
> the microamps reading. But instead, nothing happens! The microamps
> remain the same.
>
> Add a wide grounded ring around the plate with the microamp meter. Now
> if the crosswind deflects the electric wind, it can flow to a separate
> ground rather than going through the meter circuit. Result? No change
> in microamps during crosswinds! WEIRD!
>
> Really blast some air through the path of electric wind. Still the
> microamps remains the same (maybe it fluctuates just a bit.) Rats!
> This means I can't easily build an air-blast VandeGraaff generator
> using a small DC fan in place of a moving rubber belt. And I can't
> make a wind-speed meter with no moving parts, using deflected ion-wind
> to measure crosswise air flows or to sense wind direction. Damn.
>
> - Possible conclusion: electric wind is composed of few ions going very
> fast through a large population of neutral air molecules that move little
> or not at all.
Yes this is correct. Only they are not filamentary in the monopolar drift area
(most of their path), they spread around more or less evenly because they
repell each other. Due to frequent collisions the smoothed law of motion is:
v=µ*E (they only slightly zigzag around the field lines, which they affect
by the space charge they create)
where velocity v is in m/s, e-field E in V/m and mobility µ is 2 x 10^-4 m/s /
V/m for air ions in air (happens to be the same for positive and negative air
ions). So for an average field of 10^6 V/m (1 kV for each mm of gap, about the
max you can do when one of your electrodes is sharp as in the present case) you
get a velocity of 2 x 10^-4 / 10^6 = 200 m/s. The neutrals are much slower as
you observed, about 100 times less. The neutral wind is what is called
inappropriately the ion wind, and that's what the smoke will show.
> If electric wind *had* contained many slow ions, then a
> crosswind of a few MPH would have a huge effect upon the ion paths and
> upon the meter reading.
>
> - Speculation: moving ions self-organize into very thin "filaments"
> having cores of fast-moving ions. (See Electrostatic Air Threads
> website.) Such a structure has high Reynolds number: high velocity
> attained, but without any transistion to turbulence. It's like the
> laminar smoke-stream above a cigarette.
>
> - Prediction: incense smoke will not detect electric wind paths. The
> narrow filaments made of few/fast ions will go right through the smoke
> without dragging it along. Yet the KE in this "undetected wind" will
> still be significant.
>
> - Impact on "lifter" physics: if the thin corona-wires emit just a few
> fast ions (perhaps organized as arrays of filaments, or as fast-moving 2-D
> sheets,) then any coupling to the air will be minimal, and efficiency will
> be VERY low. Thrust is low and energy is wasted, since fast ions deposit
> all their KE by impacting the foil plates, rather than by dragging large
> volumes of air along slowly. The high velocity of the ions is "shorting
> out" the lifter supply but without creating wind.
Efficiency is indeed very low a few % at most, but the ions don't short out the
supply in fact, they hit a neutral at least every micron, can't remember the
exact figure.
Michel
>
> - "Lifter" possibilities: If there was a way to force the fast ions to
> slow down and drag more neutral air along, then "lifter" efficiency might
> increase drastically. It's like the wide 1980s turbofan engines, versus
> the small-diameter 1950s airline engines.
>
> What happens if we place some high-freq deflection electrodes near the
> path of the electric wind in a lifter? Perhaps if we can wiggle the fast
> ion trajectories rapidly back and forth, any filament-shaped flows will be
> disrupted, and the electric wind will become a slower, large-volume flow.
> Turn on the high-freq "turbulence" electrodes, and suddenly the thrust
> increases? This is just one more idea I've never tried testing.
>
>
>
> (((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))
> William J. Beaty SCIENCE HOBBYIST website
> billb at amasci com http://amasci.com
> EE/programmer/sci-exhibits amateur science, hobby projects, sci fair
> Seattle, WA 425-222-5066 unusual phenomena, tesla coils, weird sci
>
