Force of attraction between a charged object and neutral object follows 1/r law
frank...@yahoo.com
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
hanging sphere.
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
paper.
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
xxxxxx
x x |
x x | - wire hung down from end of wire
xxxxxx |
xx |
xx 0 - aluminum sphere
xx
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
surprising.
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:
http://www.geocities.com/franklinhu/theory.html
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
invalid.
I open this experiment to peer review.
fhuexp
Helmut Wabnig
>I open this experiment to peer review.
>
Idiotic hope.
Learn to measure.
And think.
You know that "neutral" charge is a charge of "zero",
you do know, do you?
Ever heard about "potential difference"
You are an (......) (your choice)
w.
John C. Polasek
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
out.
John Polasek
http://www.dualspace.net
frank...@yahoo.com
John C. Polasek wrote:
> 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.
There is a 1/r magnetic field strength relationship for the field
surrounding a straight wire. I think this is what you were referring
to, and this does not predict the strength of the electrostatic field
surrounding a straight wire. I have not found any direct examples of
how the electrostatic field strength varies with distance from a wire,
do you know of any, or some bit of logic that shows the electrostatic
field strength is the same as the magnetic field strength? However,
even if you can show this, the setup I used wouldn't seem applicable
since the formula relies on the wire extending infinitely up and down
in the area being measured, whereas my experiment has the wire
terminating above the area being measured. According to our standard
knowledge of fields, this should just radiate out in a spherical
pattern whether it terminates in a pointy wire or a large ball, the
field shape should be the same extending below the wire.
There is also a practical problem with terminating at a point wire.
Such points cannot contain high electrostatic charge and tend to bleed
off the charge into space. A large smooth ball helps to distribute the
charge so it doesn't escape out so easily and allows a large
electrostatic field to develop.
You are correct that I cannot shield against the total effects of the
nearby Van De Graff generator and the suspending wire. However, I did
perform this experiment using a 10in piece of charged PVC pipe held in
the vertical position. This would help eliminate some of the stray
electrostatic sources and would act like a straight wire to a certain
extent. I was also able to observe a 1/r force-distance relationship in
this setup as well. However, the best way to test this would be to use
a torsion-balance setup which uses a spherical charged and uncharged
ball.
PD
frank...@yahoo.com 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.
In that case, you're not searching the web carefully or thoroughly
enough. Of course, if you took the time to buy a textbook and read it,
you would see that the explanation is not only available but easily
found.
On the other hand, it is still quite possible to find the answer on the
web, if you know what you're looking for.
http://www.glenbrook.k12.il.us/gbssci/phys/Class/estatics/u8l1e.html
>
> 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.
Excellent!
>
> 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.
A torsion balance is easy to make, especially if one is only interested
in uncalibrated measurements suitable for determining ratios (which is
what you're doing) and as long as you're ok with 5% precision.
> 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
> hanging sphere.
Unfortunately, this won't be a spherically symmetric field once you
bring a charged or neutral conductor in the vicinity of it, because the
sphere is a conducting sphere and the charge redistributes itself on it
to make the surface an equipotential. You would be better off using a
charged ping-pong ball.
That's correct. See my comments above about your assumptions, however.
>
> 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.
Yup, and one should check your experimental set-up as well as check
what the theory says in a case like this.
>
> 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.
I did this experiment as an undergraduate. It is tricky to do right.
frank...@yahoo.com
PD wrote:
> frank...@yahoo.com 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.
>
> In that case, you're not searching the web carefully or thoroughly
> enough. Of course, if you took the time to buy a textbook and read it,
> you would see that the explanation is not only available but easily
> found.
> On the other hand, it is still quite possible to find the answer on the
> web, if you know what you're looking for.
> http://www.glenbrook.k12.il.us/gbssci/phys/Class/estatics/u8l1e.html
>
I have seen this article, it does not indicate the force/distance
relationship - only that neutral matter can be attracted to a charge.
Can you find one which does indicate the force/distance relationship?
> >
> > 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.
>
> Excellent!
>
> >
> > 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.
>
> A torsion balance is easy to make, especially if one is only interested
> in uncalibrated measurements suitable for determining ratios (which is
> what you're doing) and as long as you're ok with 5% precision.
>
>
> > 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
> > hanging sphere.
>
> Unfortunately, this won't be a spherically symmetric field once you
> bring a charged or neutral conductor in the vicinity of it, because the
> sphere is a conducting sphere and the charge redistributes itself on it
> to make the surface an equipotential. You would be better off using a
> charged ping-pong ball.
I'm not sure I understand your concern. An equipotential surface is
what I was trying to get with the conducting sphere. I don't bring any
conductors near the sphere, so where is the problem? I would agree a
ping-pong ball would be better. I did repeat the experiment with a
statically charged PVC pipe held in the vertical position and got the
same results.
Are you sure you did this experiment (neutral/charged relationship) and
not the normal charged/charged relationship experiment? Can you tell me
if you found the 1/r relationship? This is what I want to confirm.
PD
A charged conductor (an equipotential surface) will not necessarily
have a field that goes as 1/r^2, even if the conductor is a sphere.
We found a relationship that was something in between a 1/r^2
dependence and a 1/r^3 dependence. We showed in our analysis that some
of the geometric features of the experiment could reasonably account
for the non-ideal behavior.