Re: Force of attraction between a charged object and neutral object follows 1/r law
- From: John C. Polasek <jpolasek@xxxxxxxxxx>
- Date: Tue, 27 Sep 2005 13:27:55 GMT
On 26 Sep 2005 22:27:00 -0700, franklinhu@xxxxxxxxx wrote:
>It is well known that the force between charged objects falls as 1/r^2.
>But what about the force between a charged object and a neutrally
>charged object? In intensive search of the internet shows that it is
>well understood that a charged body can attract an uncharged body, but
>the nature and strength of the force is never explained.
>Since I couldn't find any experimental results that describe this
>force, I decided to do my own experiment to determine the relationship
>between force and distance for a charged and neutral body.
>It would have been ideal to use a torsion balance which is often used
>to characterized the force between charged objects, but I don't have
>access to this very expensive piece of lab equipment. So I created my
>own setup to determine the force relationship.
>For a strong electrostatic source, I took a Van De Graff generator and
>I hung a straightened coat hanger wire across the top. I then dropped a
>wire off the end of the wire and hung an aluminized ball at the end.
>This effectively created a condentrated spherical electrostatic field
>of constant stregnth which was far enough away from the Van De Graff
>generator so that I would only see the electrostatic field from the
>If I take a bit of aluminnum and bring it near the sphere, it will be
>attracted to the charged sphere and jump up to the sphere if you get
>close enough. This is similar to how a comb can attract neutral bits of
>To determine the nature of the force verus distance, I created test
>masses out of aluminum foil. I started with a 1cm^2 piece. Doubling
>that produced a 2cm^2 mass which was exactly twice as much as the first
>test mass and so on for increasing masses. Each of these masses was
>crumpled into a ball of approximately the same size.
>Since I know what the relative mass of each of the masses are, I can
>measure the distance at which the test mass overcomes the force of
>gravity and is attracted upward toward the charged sphere. The mass
>tells me how much force is present and the distance can be measured, so
>this provides a way to measure the effect of force over distance.
>The way I measured the distance was by placing the test mass on a non
>conducting tip (nylon bristle) which was mounted on a tripod directly
>below the charged ball. I could adjust the test mass distance using the
>tripod and when the test mass left the tip, I could measure the
>distance on a scale attached to the tripod.
>In ASCII, the setup looked something like this:
> ___________________ - wire attached to top of generator
> x x |
> x x | - wire hung down from end of wire
> xxxxxx |
> xx |
> xx 0 - aluminum sphere
> xx * - test mass
> xx ^
> xx |
> xxxxxxxxxx / \ -tripod
>I performed the experiment with masses range from .5 to 18 cm^2 of
>aluminum foil. The result was that the relation ship of the force over
>distance was 1/r.
>This result could not be predicted from standard theories of how the
>attraction of a neutral body to a charged body due to the separation of
>charges within the neutral body. Such a theory would predict a force
>relationship closer to 1/r^3, so this result is very unexpected and
>This significance of this discovery is that it shows that we really
>don't fully understand the nature of how a neutral body is attracted to
>a charged object on a macroscopic level. There is a huge difference
>between a 1/r force and a 1/r^3 force. This is a case where you cannot
>do "arm-chair" physics and presume you know how forces react by
>calculating them with pen and paper. You always must go into the field
>and directly measure the empirical result. In this case, there is a
>huge and unexplained mismatch.
>It is also suprising that I could find no other reference to
>experiments like this in the literature. If it really were as simple as
>1/r, then I would have expected that this experiment would have been
>routinely performed and the result posted alongside the results for
>charged bodies which is 1/r^2.
>I would be very interested if someone could repeat this experiment
>using the same setup that I used or using a torsion balance. Since the
>result is not well known, it might make a good topic for a published
>paper. (Although I can hardly believe that nobody has done this simple
>and fundamental experiment before.) Perhaps someone else can fill me in
>on previous results in this area if they exist.
>The original motivation for this experiment was to determine if gravity
>could be caused by an electrostatic charge. This is part of my "Theory
>of Everything" which can be found at:
>I was looking for a 1/r^2 result for the attraction of a neutral body
>to a charged source. I did not find that result, but found that the
>force was a stronger 1/r force. However, in my model, the net
>graviational force is due to the attraction of neutral matter minus the
>repulsion due to all objects having a residual net positive charge. So
>the 1/r force might still be reduced to a 1/r^2 force. However, I
>suspect that there are other mechanisms in play if the electrostatic
>force is truly responsible for gravity.
>In any case, one of the arguments used against an electrostatic graivty
>is that the force relationship should be 1/r^3. My experiments have
>shown this to be false and at the very least, we don't understand how
>the attraction actually works until somebody comes up with a formula
>that can explain the 1/r force relationship or why my experiment was
>I open this experiment to peer review.
You are deceiving yourself, to think the electric field comes from
your terminal ball. The ball and wire are obviously at equipotential.
The field intensity from the straight wire will be vastly greater than
from the ball, it seems to me. The straight wire would I believe give
you a 1/r field, but with an ill defined geometry it would be wrong to
predict a straight inverse or inverse squared result.
Try it without the ball and see if there is any difference. It might
be instructive. It's nice to see someone here actually try something
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