An "invisible wall" created by static electricity?

RGClark

I copied below a post to sci.astro on a strange phenomenon involved with high-voltage static electricity. It concerns the creation of an "invisible wall" due to electrostatic charge from a large sheet of polypropelene film moving at high speed at a 3M plant:

David Swenson's electrostatic "invisible wall".
http://amasci.com/weird/unusua*l/e-wall.html

A perhaps related phenomenon is illustrated by this experiment on Hero's
Fountain:

Expt 013 -- Hero's Fountain.
http://chemmovies.unl.edu/chem*istry...mos/BD013.html

Here, a electrostatically charged balloon held near a Hero's Fountain
causes the fountain to dissipate. See the video at the link in step #4
in the Procedure section.

In the post to sci.astro, I suggest the effect at the 3M plant was due to the effect electrostatic charge has on polar molecules such as water. What would really seal this would be to see if the same "invisible wall" was observed to effect materials composed of non-polar molecules.
I would like to be able to estimate the possible force produced on a polar molecule such as water by an electrostatic charge and what would be the magnitude of the electrostatic voltage created by a Van de Graaff generator dependent on its dimensions.
Anyone know of any such formulas for this?


Bob Clark




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Newsgroups: sci.astro, sci.physics, sci.engr.mech, sci.space.policy, sci.chem
From: "Robert Clark" <rgregorycl...@yahoo.com>
Date: 10 May 2005 10:30:30 -0700
Local: Tues,May 10 2005 1:30 pm
Subject: Re: An "invisible wall" for ground-based scopes.[Re: An atmospheric envelope for ground-based telescopes.]

George Dishman wrote:
> <rgregorycl...@yahoo.com> wrote in message
> news:1115572029.828589.36910@z14g2000cwz.googlegroups.com...
> > George Dishman wrote:
> >> "Robert Clark" <rgregorycl...@yahoo.com> wrote in message
> >> news:1115565190.846069.40280@f14g2000cwb.googlegroups.com...
> >> > Astronomers like to wring every last photon from their observations so
> >> > having a physical cover at the top of the shroud may be problematical.
> >> > The tapered tower providing constant pressure with altitude idea is
> >> > also problematical.
> >> > So after a web search I was interested to see this report:
> >> > David Swenson's electrostatic "invisible wall".
> >> > http://amasci.com/weird/unusua*l/e-wall.html


> The page you quote is entirely speculative, they
> didn't actually find out what caused the effect.
> I know of a situation where there was a single
> turn of wire on the ground. Someone walking along
> put one foot in it and found he couldn't move.
> The coil undergoing a short circuit test and was
> carrying several thousand amps DC. It wasn't a
> direct force effect, the field was numbing the
> nerves in the guys legs. There are many
> possibilities in the case of the 3M effect and
> until they figure it out, reproduce it and find
> out how to control it you are wasting your time.
> ...


That the phenomenon observed was a true effect is suggested by
electrostatic experiments such as these:

J4-12: ELECTROSTATIC FORCE - MOVING LUMBER.
PURPOSE: To demonstrate polarization of water molecules.
http://jedlik.phy.bme.hu/~hartlein/p...cdem/j4-12.htm

This is from a page of undergraduate physics experiments. It
demonstates the effect of electrostatic charge on polar molecules such
as water. A piece of lumber is made to rotate over a low friction
support by bringing close a rod charged with static electricity by
rubbing with a wool cloth. The effect arises from the polar molecules
of water in the wood.
This is effect is also illustrated by this experiment:

J4-11: POLAR AND NONPOLAR LIQUIDS
PURPOSE: To demonstrate that non-uniform electric fields produce a
force on polar molecules.
http://jedlik.phy.bme.hu/~hartlein/p...cdem/j4-11.htm

Here a stream of water is deflected by a source of electrostatic
charge while a stream of carbon tetrachloride (CCl4), a non-polar
molecule, is not.

The static charge built up on a rod or a balloon by rubbing with a
cloth amounts to perhaps a few thousand volts. Dave Swenson in the
phenomenon observed at the 3M plant estimated the static electricity was in the megavolt range. Human beings and all living beings are composed of
mostly liquid water. Then considering the deflections of water at a few
thousand volts in these lab experiments, it is conceivable that voltages a thousand times higher could have the effect observed at the
3M plant.
If this is the explanation then this "invisible wall" would work
against human beings and other living things but not inanimate objects
that did not contain water.
However, it is known that large Van de Graaff generators can produce
static voltages in the megavolt range:

Construction of the Van de Graaff Generator.
http://www.mos.org/sln/toe/con*struction.html

Have experiments been done on the effect of such large generators on
large amounts of water?

Note that with this explanation of the 3M plant phenomenon it wouldn't
work to create an invisible wall around our telescope because it
wouldn't effect the non-polar molecules in the air.
The method of ionizing the air with lasers might still work though.


Bob Clark

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RGClark

This board sometimes inserts asterisks arbitrarily in links.
Here the corrected links:

David Swenson's electrostatic "invisible wall".
http://amasci.com/weird/unusual/e-wall.html

Expt 013 -- Hero's Fountain.
http://chemmovies.unl.edu/chemistry/beckerdemos/BD013.html

Construction of the Van de Graaff Generator.
http://www.mos.org/sln/toe/construction.html


Bob Clark

Mk

I've been here for a while, and I've never ever seen the astrerisks before! That's strange. Anyone have an explination for it?

RGClark

In the 3M phenomenon, there appears to be a repulsive effect.
I presume there is also a repulsive effect here in this case as well:

Expt 013 -- Hero's Fountain.
http://chemmovies.unl.edu/chemistry/...mos/BD013.html

since in the video the fountain is made to stop when the charged balloon is brought close to the stream.

But this page says a stream of falling water will be *attracted* to a charged balloon:

Lesson 1: Charge and Charge Interactions
Polarization.
http://www.glenbrook.k12.il.us/gbssc...ics/u8l1e.html

Also curious is what this page on this experiment says of it:

J4-11: POLAR AND NONPOLAR LIQUIDS.
"NOTE: Although the demonstration apparently works as predicted, this demonstration does not work according to theory, and should probably not be done and explained in the traditional manner."
http://www.physics.umd.edu/lecdem/se...osj4/j4-11.htm

And in this video version of the moving lumber experiment, the lumber is *attracted* to the charged rod whether it is charged positive or negative:

Question #131
http://www.physics.umd.edu/lecdem/ou...arch7/q131.htm



Bob Clark

zoobyshoe

Thoughts:

I've done some reading about electrostatic motors like the ones Ben Frankin made. They generally work on the principle that some element of the rotor is first attracted to an opposite charge, approaches closer, then becomes similarly charged itself and is repelled. I would think this "wall" is the same thing. The workers meet a sudden resistance when they get close enough to become charged to the same polarity as the film.

I don't think the wall has anything to do with water molecules. In fact the link is pretty clear that the effect was not present during times of high humidity.