A poll: Will a neutral and charged conductor be attracted to one another?

[larry...@softhome.net]

Here's a basic question in electrostatics that I'd like to have some answers on, just to see how diverse the responses are:

Will two conductors, one neutral the other charged, be attracted to one another?

My answer: I did say no to start with, but on further thought--yes.

Regards,

Larry.

[Bert Hickman]

It may depend on the size of the conductors. Attraction will always
occur with larger, multi-particle conductors as charges within the
conductor shift to form a dipole with opposite polarity charges
concentrating on the side of the neutral conductor that is closest to
the nearby charged conductor.

But will a fundamental neutral and a fundamental charged particle (such
as a neutron and a proton or electron) show any attraction? I don't
think so...

Bert
--
Bert Hickman
Stoneridge Engineering
http://www.capturedlightning.com
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[Jos Bergervoet]

On 7/30/2012 7:48 PM, Bert Hickman wrote:
> larry...@softhome.net wrote:
>> Here's a basic question in electrostatics that I'd like to have some
>> answers on, just to see how diverse the responses are:
>>
>> Will two conductors, one neutral the other charged, be attracted to
>> one another?
>>
>> My answer: I did say no to start with, but on further thought--yes.
>>
>> Regards,
>>
>> Larry.
>>
>
> It may depend on the size of the conductors. Attraction will always
> occur with larger, multi-particle conductors as charges within the
> conductor shift to form a dipole with opposite polarity charges
> concentrating on the side of the neutral conductor that is closest to
> the nearby charged conductor.

Looks like the van der Waals force between two
*uncharged* objects, where random fluctuations
create a temporary dipole in one object, and the
other reacts in the way you describe! vdW force
drops like 1/r^7, IIRC. What would you expect
for the case here?

> But will a fundamental neutral and a fundamental charged particle (such
> as a neutron and a proton or electron) show any attraction?

Good question! But the example may not be
suitable.. The neutron is not an elementary
particle (as it contains three quarks) so it
might develop a dipole like you describe for
an ordinary multi-particle conductor.

A neutrino and an electron would be better.
But even then, your question (will they show
any attraction?) has the answer "yes!" They
will feel the Z-field (Z-boson exchange) since
they both have weak hypercharge (But the "weak
force" falls of exponentially, much faster
than the 1/r^n behavior for electric forces,
so it may be negligible for this purpose.)

Actually there isn't a known ideal candidate
for an electrically neutral particle which
*also* does not feel any other force. Perhaps
dark matter consists of such non-interacting
particles, but that is exactly why they haven't
yet been identified!

--
Jos

[Salmon Egg]

In article <dea2b3e1-4f6a-406b...@googlegroups.com>,

Polls don't count. Governments or democracies cannot pass laws of nature.

The answer, of course.is that they will attract. A small charged
conductor above a large conducting plate will be attracted tp the image
incuced in the plate.

--

Sam

Conservatives are against Darwinism but for natural selection.
Liberals are for Darwinism but totally against any selection.

[glen herrmannsfeldt]

Salmon Egg <Salm...@sbcglobal.net> wrote:
(snip)

>> Will two conductors, one neutral the other charged, be
>> attracted to one another?

(snip)

> Polls don't count. Governments or democracies cannot pass laws of nature.

> The answer, of course.is that they will attract. A small charged
> conductor above a large conducting plate will be attracted tp the image
> incuced in the plate.

OK, but how about two infinite planes, zero thickness, one charged
the other not?

-- glen

[Jos Bergervoet]

I think that in this ideal case they would
attract by gravity and also by the Casimir
effect, but not by electric force!

--
Jos

[Salmon Egg]

In article <jv7klk$5i2$1...@speranza.aioe.org>,

glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:

> OK, but how about two infinite planes, zero thickness, one charged
> the other not?

Now, there is a description of a physically realizable system. :=)

[Jos Bergervoet]

On 8/1/2012 12:09 AM, Salmon Egg wrote:
> In article <jv7klk$5i2$1...@speranza.aioe.org>,
> glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:
>
>> OK, but how about two infinite planes, zero thickness, one charged
>> the other not?
>
> Now, there is a description of a physically realizable system. :=)

O, Salmon, I hope you did not start constructing them
yet! Would you please also make them zero-mass?!

(J)

[larry...@softhome.net]

On Monday, July 30, 2012 5:58:33 PM UTC+1, larry...@softhome.net wrote:
> Here's a basic question in electrostatics that I'd like to have some answers on, just to see how diverse the responses are: Will two conductors, one neutral the other charged, be attracted to one another? My answer: I did say no to start with, but on further thought--yes. Regards, Larry.

Here's a video showing nicely the effect of a conductor attracted to a charged balloon, but misinterpreted by the poster as a magnetic effect.

"Testing the Magnetic Nature of MagneGas.mp4"
http://www.youtube.com/watch?v=bFsZ1NrtIMk

Larry.

[Jos Bergervoet]

I would also think this is electrostatic attraction.
This raises a new question: which one of the objects
is the charged one here, if any?

And another question: (after reading the YouTube claim)
is it really impossible that a gas can have a magnetic
field?

--
Jos

[glen herrmannsfeldt]

Jos Bergervoet <jos.ber...@xs4all.nl> wrote:

(snip)

> And another question: (after reading the YouTube claim)
> is it really impossible that a gas can have a magnetic
> field?

Oxygen is paramagnetic, but pretty much only noticable as liquid.

The density of a gas would be low enough (not counting supercritical)
that you wouldn't see the usual magnetic effect. (Sticking to iron.)

Otherwise, would molecules of a ferromagnetic gas attract enough
to stay liquid?

-- glen

[Jos Bergervoet]

A ferromagnetic gas is most likely not possible,
as the distance between the molecules will make
their interaction too weak to get the magnetic
ordering.. (Still, I'm not sure it can be ruled
out!)

But I was of course thinking of paramagnetic
gas and then holding a very strong magnet close
to it! I don't know whether it could ever give
you enough force to explain what the video shows.
But how can Larry be so sure it doesn't?!

--
Jos

[Jos Bergervoet]

On 8/1/2012 8:44 PM, Jos Bergervoet wrote:
> On 8/1/2012 8:29 PM, glen herrmannsfeldt wrote:

..

>> Otherwise, would molecules of a ferromagnetic gas attract enough
>> to stay liquid?
>
> A ferromagnetic gas is most likely not possible,
> as the distance between the molecules will make
> their interaction too weak to get the magnetic
> ordering.. (Still, I'm not sure it can be ruled
> out!)

There you are:
http://en.wikipedia.org/wiki/Ferromagnetism#Lithium_gas

"This demonstration is the first time that ferro-
magnetism has been demonstrated in a gas."

--
Jos

[glen herrmannsfeldt]

Jos Bergervoet <jos.ber...@xs4all.nl> wrote:

(snip, I wrote)

>> Oxygen is paramagnetic, but pretty much only noticable as liquid.

>> The density of a gas would be low enough (not counting supercritical)
>> that you wouldn't see the usual magnetic effect. (Sticking to iron.)

(snip on ferromagnetic gas)

> A ferromagnetic gas is most likely not possible,
> as the distance between the molecules will make
> their interaction too weak to get the magnetic
> ordering.. (Still, I'm not sure it can be ruled
> out!)

> But I was of course thinking of paramagnetic
> gas and then holding a very strong magnet close
> to it! I don't know whether it could ever give
> you enough force to explain what the video shows.
> But how can Larry be so sure it doesn't?!

I didn't see the video. Pouring liquid oxygen
through a magnetic field gradient does show a
visible deflection. I saw it done in a physics
lecture demonstration once.

-- glen