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Magnetic Idyll
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Sue...
science forum Guru


Joined: 08 May 2005
Posts: 2684

PostPosted: Sun Jul 09, 2006 8:53 am    Post subject: Re: Magnetic Idyll Reply with quote

Tom Roberts wrote:
Quote:
Edward Green wrote:
The formal simularity of the Coriolis force and the Lorentz force law
-2w x v vs. -qB x v
suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.

Not really.

The Lorentz force law, written in terms of physical quantities in 4-d
spacetime using the language of tensors is:
f = q F.U
Where f is the covariant force 4-vector, F is the electromagnetic field
2-form (includes both B and E), and U is the 4-velocity of the particle
with charge q.

Using the same language, the "Coriolis force" is:
f = 0

I see no similarity here at all (Smile).

Because you did your transformation wrong so why the
big grin ?

http://farside.ph.utexas.edu/teaching/jk1/lectures/node28.html

Quote:

[Note, please, that "Coriolis force' is fictitious -- merely
an artifact of one's coordinates (your formula applies only to
rotating coordinates). It is _not_ a tensor; Lorentz force is.]


Besides, if this were truly a good analogy there would be an
electromagnetic analog to "centrifugal force" (which is usually much
larger than the "Coriolis force"). With your identification above, the
EM analogy would be B x (B x r), which does not appear in any usual
formula of classical electrodynamics that I am aware of (one applies
"centrifugal force" to a particle sitting still on a carousel, but a
charge sitting still does not "feel" B at all).

What in the world do you think moves the currents toward
surface in this experiment ?

http://www.esa.int/SPECIALS/GSP/SEM0L6OVGJE_0.html


Oh! ... I forgot. That is probably something you'd really
rather not see isn't it.

Sue...


Quote:


Bill Hobba wrote:
Cross products appear all over the place in physics. That does not imply
they are related any more than bacteria growth and monetary growth with
interest being exponential implies bacteria are related to money.

Lest anybody wonder why such different phenomena are described by
similar mathematics, let me point out that one makes similar
_approximations_ here: in the real world, the bacteria do not really
have exactly equal and constant reproduction rates, and the money does
not have exactly constant interest rate; by _approximating_ those as
constant one obtains similar differential equations with similar solutions.


Tom Roberts
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Sorcerer1
science forum Guru


Joined: 09 Jun 2006
Posts: 410

PostPosted: Sun Jul 09, 2006 8:36 am    Post subject: Re: Magnetic Idyll Reply with quote

"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:1152400330.145973.161020@s13g2000cwa.googlegroups.com...
| The formal simularity of the Coriolis force and the Lorentz force law
|
| -2w x v vs. -qB x v
|
| suggests that the magnetic field may correspond to a local rotation of
| space (inertial coordinate system) as seen by charge vs. that seen by
| mass.
|
| On the pro-side, one can easily list more hints that magentic effects
| have to so with something or other rotating. On the con side, there
| doesn't seem to be an obvious way in incorporate the centrifugal force
| into this analogy -- for purposes of "magnetic rotation", the test
| particle is always on axis.
|
| Comments?

1) Coriolis is a change of reference frame, not a force.
The laws of physics in this frame of reference say the ball curves
without being accelerated:
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/gifs/coriolis.mov

2) Single phase induction motors normally rotate in either direction, they
have
a starting winding to determine which. The Lorentz force is nothing more
than the equivalent of squeezing a dough ball so that it spreads out, or
stretching it so that it spreads in. A pastry chef understands physics
better than Lorentz, he knows what to do with a rolling pin.

3) This bottle is juggled from Mickey's left hand to his right and
back again. No forces are involved. If there were friction between
the bottle and the Mickey's frame then the bottle frame and Mickey
frame would try to combine. Then you have force.
http://www.androcles01.pwp.blueyonder.co.uk/Wilson/RotateMickeyLarge.gif

Androcles.
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Tom Roberts
science forum Guru


Joined: 24 Mar 2005
Posts: 1399

PostPosted: Sun Jul 09, 2006 5:34 am    Post subject: Re: Magnetic Idyll Reply with quote

Edward Green wrote:
Quote:
The formal simularity of the Coriolis force and the Lorentz force law
-2w x v vs. -qB x v
suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.

Not really.

The Lorentz force law, written in terms of physical quantities in 4-d
spacetime using the language of tensors is:
f = q F.U
Where f is the covariant force 4-vector, F is the electromagnetic field
2-form (includes both B and E), and U is the 4-velocity of the particle
with charge q.

Using the same language, the "Coriolis force" is:
f = 0

I see no similarity here at all (Smile).

[Note, please, that "Coriolis force' is fictitious -- merely
an artifact of one's coordinates (your formula applies only to
rotating coordinates). It is _not_ a tensor; Lorentz force is.]


Besides, if this were truly a good analogy there would be an
electromagnetic analog to "centrifugal force" (which is usually much
larger than the "Coriolis force"). With your identification above, the
EM analogy would be B x (B x r), which does not appear in any usual
formula of classical electrodynamics that I am aware of (one applies
"centrifugal force" to a particle sitting still on a carousel, but a
charge sitting still does not "feel" B at all).


Bill Hobba wrote:
Quote:
Cross products appear all over the place in physics. That does not imply
they are related any more than bacteria growth and monetary growth with
interest being exponential implies bacteria are related to money.

Lest anybody wonder why such different phenomena are described by
similar mathematics, let me point out that one makes similar
_approximations_ here: in the real world, the bacteria do not really
have exactly equal and constant reproduction rates, and the money does
not have exactly constant interest rate; by _approximating_ those as
constant one obtains similar differential equations with similar solutions.


Tom Roberts
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Bill Hobba
science forum Guru


Joined: 02 May 2005
Posts: 2138

PostPosted: Sun Jul 09, 2006 1:24 am    Post subject: Re: Magnetic Idyll Reply with quote

"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:1152400330.145973.161020@s13g2000cwa.googlegroups.com...
Quote:
The formal simularity of the Coriolis force and the Lorentz force law

-2w x v vs. -qB x v

suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.

Cross products appear all over the place in physics. That does not imply
they are related any more than bacteria growth and monetary growth with
interest being exponential implies bacteria are related to money.

Quote:

On the pro-side, one can easily list more hints that magentic effects
have to so with something or other rotating.

Sure - usually electron spin or electrons 'rotating' around atoms. Of
course these are quantum effects but in a very crude way it is rotation.

Bill

Quote:
On the con side, there
doesn't seem to be an obvious way in incorporate the centrifugal force
into this analogy -- for purposes of "magnetic rotation", the test
particle is always on axis.

Comments?
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Sue...
science forum Guru


Joined: 08 May 2005
Posts: 2684

PostPosted: Sat Jul 08, 2006 11:33 pm    Post subject: Re: Magnetic Idyll Reply with quote

Edward Green wrote:
Quote:
The formal simularity of the Coriolis force and the Lorentz force law

-2w x v vs. -qB x v

suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.

On the pro-side, one can easily list more hints that magentic effects
have to so with something or other rotating. On the con side, there
doesn't seem to be an obvious way in incorporate the centrifugal force
into this analogy -- for purposes of "magnetic rotation", the test
particle is always on axis.

Comments?

What rotates is an ensemble of electric charges.
"The origin of permanent magnetism"
http://farside.ph.utexas.edu/teaching/302l/lectures/node62.html
"Visualizations"
http://web.mit.edu/8.02t/www/802TEAL3D/teal_tour.htm

If you take a Machian view of inertia, the the dielectric propeties
of free space don't make too bad an analogy to the gravitational/
inertial field established by nearby matter.

There are numerous way to incorporate the
magnetic force into gravity/inertia. You are building bricks
with little houses. Try it the other way round. Surprised)

http://www.esa.int/SPECIALS/GSP/SEM0L6OVGJE_0.html
http://www.mypage.bluewin.ch/Bizarre/GRAV.htm

Sue...
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Edward Green
science forum addict


Joined: 21 May 2005
Posts: 95

PostPosted: Sat Jul 08, 2006 11:12 pm    Post subject: Magnetic Idyll Reply with quote

The formal simularity of the Coriolis force and the Lorentz force law

-2w x v vs. -qB x v

suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.

On the pro-side, one can easily list more hints that magentic effects
have to so with something or other rotating. On the con side, there
doesn't seem to be an obvious way in incorporate the centrifugal force
into this analogy -- for purposes of "magnetic rotation", the test
particle is always on axis.

Comments?
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