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| John Schoenfeld |
 Posted: Wed Jun 02, 2004 3:36 pm |
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Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)? |
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| Robert J. Kolker |
| Posted: Wed Jun 02, 2004 3:43 pm |
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John Schoenfeld wrote:
[quote:6c5d0ce480]Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)?
[/quote:6c5d0ce480]
It will have to do. The only magenetic fields that have been seen are
solenoidal and at right angles to the current. If someone does come up
with a magnetic monople Maxwells's Equations will have to be altered.
Maxwell's Equations were not graven on tablets of stone and brought down
from a mountain peak. The were formulated to describe and predict
certain phehomena some of which were known empirically. M.E. cannot be
deduced a prior from a necessary synthetic a prior principle.
Bob Kolker |
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| Timo Nieminen |
| Posted: Wed Jun 02, 2004 4:58 pm |
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| Michael Moroney |
| Posted: Wed Jun 02, 2004 5:19 pm |
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"Robert J. Kolker" <robert_kolker@hotmail.com> writes:
[quote:c75755790a]John Schoenfeld wrote:
Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)?
It will have to do. The only magenetic fields that have been seen are
solenoidal and at right angles to the current. If someone does come up
with a magnetic monople Maxwells's Equations will have to be altered.
[/quote:c75755790a]
As written, Maxwell's Equations describe a world with no such thing as
magnetic monopoles. If magnetic monopoles exist, you'd have to change
the div B term, and most likely the curl E term (a "current" of monopoles
would generate an electric field around it). The modified Maxwell's
Equations would be symmetric, you could swap every electric and magnetic
field reference and every electric and magnetic "charge" and it would be
unchanged.
--
-Mike |
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| John Schoenfeld |
| Posted: Wed Jun 02, 2004 7:54 pm |
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Timo Nieminen <timo@physics.uq.edu.au> wrote in message news:<Pine.LNX.4.50.0406030856080.11833-100000@localhost>...
[quote:492e0f7e31]On Thu, 2 Jun 2004, John Schoenfeld wrote:
Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields?
No. See, for example, Jackson, Classical electrodynamics, 3rd ed, section
6.11.
div B = 0 is an experimental observation.
[/quote:492e0f7e31]
Yes an observation from steady currents. The observation does not
conclude in any way that all magnetic fields are caused by charges in
motion, does it? |
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| Sam Wormley |
| Posted: Wed Jun 02, 2004 8:00 pm |
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John Schoenfeld wrote:
[quote:75fceff754]
Timo Nieminen <timo@physics.uq.edu.au> wrote in message news:<Pine.LNX.4.50.0406030856080.11833-100000@localhost>...
On Thu, 2 Jun 2004, John Schoenfeld wrote:
Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields?
No. See, for example, Jackson, Classical electrodynamics, 3rd ed, section
6.11.
div B = 0 is an experimental observation.
Yes an observation from steady currents. The observation does not
conclude in any way that all magnetic fields are caused by charges in
motion, does it?
[/quote:75fceff754]
John--Describe how a magnetic field arises in permanent magnet
and the relevance of div B = 0 . |
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| John Schoenfeld |
| Posted: Wed Jun 02, 2004 8:02 pm |
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"Robert J. Kolker" <robert_kolker@hotmail.com> wrote in message news:<aSrvc.37813$eY2.10359@attbi_s02>...
[quote:ffddd4b801]John Schoenfeld wrote:
Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)?
It will have to do. The only magenetic fields that have been seen are
solenoidal and at right angles to the current. If someone does come up
with a magnetic monople Maxwells's Equations will have to be altered.
[/quote:ffddd4b801]
I don't see why they would require alteration since the equations are
considering only the special case of steady currents which may indeed
have a unique property of inducing solenoidal magnetic fields. I could
probably arrange solenoidal gravitational fields given some odd mass
arrangement, but this does not mean all gravitational fields are
necessarily solenoidal, does it?
[quote:ffddd4b801]Maxwell's Equations were not graven on tablets of stone and brought down
from a mountain peak. The were formulated to describe and predict
certain phehomena some of which were known empirically. M.E. cannot be
deduced a prior from a necessary synthetic a prior principle.
[/quote:ffddd4b801]
Thanks for the tip.
> Bob Kolker |
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| tj Frazir |
| Posted: Wed Jun 02, 2004 8:26 pm |
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If you spin a ball wount boath ends allways spin ¿ A diapole is 90
deg from electron and if dipoles all point in one direction pos or neg
it conductable as at one time the electron may belong to boath atoms at
once and will take the orbit of lest resistance of beeing pushed into
the orbit.
If the orbits dont overlap then its insulated .
If the orbits overlap but the slight change in direction takes more
energy as resistance. |
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| Timo Nieminen |
| Posted: Wed Jun 02, 2004 8:27 pm |
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On Thu, 2 Jun 2004, John Schoenfeld wrote:
[quote:9bf8648623]Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Thu, 2 Jun 2004, John Schoenfeld wrote:
Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields?
No. See, for example, Jackson, Classical electrodynamics, 3rd ed, section
6.11.
div B = 0 is an experimental observation.
Yes an observation from steady currents.
[/quote:9bf8648623]
No. It's from observations of steady currents, slowly-varying currents,
rapidly varying currents, and zero currents.
It's simply the non-observation of magnetic charge. First noted, AFAIK, by
Gilbert back in around 1600.
[quote:9bf8648623]The observation does not
conclude in any way that all magnetic fields are caused by charges in
motion, does it?
[/quote:9bf8648623]
To stray somewhat from classical EM, is there any particle with an
intrinsic magnetic moment? Is the field from such a particle caused by
charges in motion?
Do note that people have looked for, and do look for, magnetic monopoles.
These people do so because there is no fundamental reason why they should
not exist according to classical EM theory.
Note also that the necessary modifications to the Maxwell equations if
magnetic monopoles are found have been known for a long time. 1931 if not
earlier (possibly much earlier).
--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html |
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| Old Man |
| Posted: Wed Jun 02, 2004 10:20 pm |
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"John Schoenfeld" <j.schoenfeld@programmer.net> wrote in message
news:a98beaaa.0406021336.196c4a30@posting.google.com...
[quote:dab150776c]Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)?
[/quote:dab150776c]
Maxwell's equations can be modified to be completely
symmetric in electric and magnetic fields. This allows
magnetic, as well as electric monopoles. Because magnetic
monopoles aren't observed, we do nothing more than snip
out a few terms to obtain what is commonly known as
"Maxwell's Equations".
Here's a link to hypothetical magnetic monopoles:
http://www.iw.net/~jakoepke
[Old Man] |
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| Gregory L. Hansen |
| Posted: Thu Jun 03, 2004 4:29 am |
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In article <a98beaaa.0406021336.196c4a30@posting.google.com>,
John Schoenfeld <j.schoenfeld@programmer.net> wrote:
[quote:79845eb08d]Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)?
[/quote:79845eb08d]
There's no theoretical reason to prohibit magnetic monopoles. It's an
experimental matter.
More precisely, it's an experimental matter as to whether all particles
have the same ratio of electric to magnetic charge. As long as the ratio
is the same, the fields can be transformed to distribute the charge among
electric and magnetic monopoles as you please, and it's just a convention
to set div B = 0.
If a magnetic monopole was found, that would explain the quantization of
charge. But there's no reason I can think of that quantized charges must
imply magnetic monopoles.
Jackson discusses these things with some sophistication in section 6.12.
--
"Let us learn to dream, gentlemen, then perhaps we shall find the
truth... But let us beware of publishing our dreams before they have been
put to the proof by the waking understanding." -- Friedrich August Kekulé |
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| Richard Herring |
| Posted: Thu Jun 03, 2004 6:29 am |
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In message <a98beaaa.0406021802.20b74de4@posting.google.com>, John
Schoenfeld <j.schoenfeld@programmer.net> writes
[quote:36256b644f]"Robert J. Kolker" <robert_kolker@hotmail.com> wrote in message
news:<aSrvc.37813$eY2.10359@attbi_s02>...
John Schoenfeld wrote:
Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)?
It will have to do. The only magenetic fields that have been seen are
solenoidal and at right angles to the current. If someone does come up
with a magnetic monople Maxwells's Equations will have to be altered.
I don't see why they would require alteration since the equations are
considering only the special case of steady currents
[/quote:36256b644f]
Really? Which part of Maxwell's equations implies steady current?
--
Richard Herring |
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| Sam Wormley |
| Posted: Thu Jun 03, 2004 7:04 am |
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| Guest |
| Posted: Thu Jun 03, 2004 8:53 am |
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j.schoenfeld@programmer.net (John Schoenfeld) wrote in message news:<a98beaaa.0406021336.196c4a30@posting.google.com>...
[quote:f085b7f482]Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)?
[/quote:f085b7f482]
Nobody has mentioned the Dirac magnetic monopole quantization
condition. (In this thread, as far as I've seen, anyway.)
Provided you satisfy this condition, you can mod Maxwell's
equations to include magnetic charge and current. And that's
the signature most people use to look for magnetic charge.
Other than that, other people's comments have covered things
pretty well.
Socks |
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| BllFs6 |
| Posted: Thu Jun 03, 2004 8:58 am |
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[quote:80e9803b17]Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)?
[/quote:80e9803b17]
I seem to vaguely recall that one/some/all/current? theory(s) required at least
ONE magnetic monopole in the whole"universe"....but of course if there was only
ONE your chances of detecting it would be pretty slim :)
Does anyone else know/recall such a thing and have a better recollection of the
how and why of such a thing....assuming I am remotely remembering right in the
first place?
take care
Blll |
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