magnetic field

[Ken]

Hi,

I would like to know what is a magnetic field. I mean what is it composed
of.
I searched google , asked people around me , no one seems to know.
Obviously everyone knows where how, but not what.
I thought it was electrons, but that cant be.

thank you

ken

 

[E. Rosten]

Repeating Rifle wrote:

It is only assymmetrical because there are no magnetic charges. Magnetic
charge does not appear Maxwell's equations. The symmetries or lack of them
show up more strongly in the four-vector relativistic formulations.

IIRC, magnetic charges (known also as magnetic monopoles) are
theoretically possible (according to some physicists). This leads to the
very minor addition to Maxwell's Equations that

div B = m

which is analogous to

div D = rho


However, magnetic monopoles are thought to exist at such high energies
that can never be observed.

-Ed




--
(You can't go wrong with psycho-rats.) (er258)(@)(eng.cam)(.ac.uk)

/d{def}def/f{/Times findfont s scalefont setfont}d/s{10}d/r{roll}d f 5/m
{moveto}d -1 r 230 350 m 0 1 179{1 index show 88 rotate 4 mul 0 rmoveto}
for /s 15 d f pop 240 420 m 0 1 3 { 4 2 1 r sub -1 r show } for showpage

 

[Checkmate]

On Mon, 27 Sep 2004 17:01:03 -0500, No Spam put forth the notion that...

Repeating Rifle wrote:
in article cj8eqs$9kd$0@pita.alt.net, Checkmate at LunaticFringe@The.Edge
wrote on 9/27/04 12:15 AM:


I think Heisenberg first developed that theory, but I'm not certain.


Planck introduce the concept of a quantum of energy in order to explain the
spectral distribution of black body radiation. Einstein and others were able
to extend the concept to explain specific heat and photoemission. Bohr first
applied it to atomic physics. Heisenberg developed the first modern theory
of quantum mechanics. Shrödinger formulated a wave equation that was much
more familiar to physicists of the day. The big surprise was that the
Schrödinger formulation gave identical results to that of Heisenberg's in
spite of appearing to be very different. The Schrödinger formulation was
much easier for making calculations while the Heisenberg formulation was
better suited to understanding essence of what quantum physics was all
about.

Bill

And I thought Checkmate was being funny. ;-)

That was the idea, anyway... tough crowd.

--
Checkmate
Copyright Š 2004
all rights reserved

 

[Tom Del Rosso]

"Repeating Rifle" <salmonegg@sbcglobal.net> wrote in message
news:BD7ED1F2.24867%salmonegg@sbcglobal.net

It is only assymmetrical because there are no magnetic charges.
Magnetic charge does not appear Maxwell's equations. The symmetries
or lack of them show up more strongly in the four-vector relativistic
formulations.

Kevin said, "a magnetic field is created as an electric field changes,
and an electric field is created as a magnetic field changes".

I thought a magnetic field is proportional to the current, not the
change in current. Whereas an induced current is proportional to the
rate of change of magnetic field. That's the assymetry I refered to,
but I'm seeking clarification. Am I wrong or are we both right?

 

[Sir Charles W. Shults III]

In a nutshell, a magnetic field is a virtual photon field where all
their spins are aligned. It is impressed on the vacuum and the photons
aren't really there at all (just like electrical charge is the emission and
absorption of virtual photons). Think of it as a spin field impressed on
the vacuum that makes any virtual photons that appear be aligned in a
specific way.

Cheers!

Sir Charles W. Shults III, K. B. B.
Xenotech Research
321-206-1840

 

[Sylvia Else]

Tom Del Rosso wrote:

"Repeating Rifle" <salmonegg@sbcglobal.net> wrote in message
news:BD7ED1F2.24867%salmonegg@sbcglobal.net

It is only assymmetrical because there are no magnetic charges.
Magnetic charge does not appear Maxwell's equations. The symmetries
or lack of them show up more strongly in the four-vector relativistic
formulations.


Kevin said, "a magnetic field is created as an electric field changes,
and an electric field is created as a magnetic field changes".

I thought a magnetic field is proportional to the current, not the
change in current. Whereas an induced current is proportional to the
rate of change of magnetic field. That's the assymetry I refered to,
but I'm seeking clarification. Am I wrong or are we both right?

If you think about it, you'll see that a constant current is equivalent
to a constant RATE OF CHANGE of charge at two places.

Sylvia.

 

[operator jay]

"Sylvia Else" <sylvia@not.at.this.address> wrote in message
news:4157853f$0$20129$afc38c87@news.optusnet.com.au...

I'm not disagreeing with Kevin, but there is a simple thought experiment
that shows how careful one must be about taking a theory, such as that
of James Clerk Maxwell, and attempting to use it as anything more than a
description.

Take two electrons, separated in space, stationary relative to some
observer. There's an electric field, obviously, but no magnetic field.
Now take another observer moving perpendicularly to the line joining the
electrons. This observe sees the electrons in motion. Electrons in
motion are an electric current, and an electric current produces a
magnetic field, so for that observer there is a magnetic field present.

So one observer finds a magnetic field present where another observer
finds none. The notion that a magnetic field has a concrete existence is
clearly problematic. This paradox doesn't appear in the theory itself,
because it simply tells you what will happen (or more exactly, what your
measurements will show). It doesn't say anything about what is "really"
there.

Sylvia.

I was told that Einstein showed that there is not actually any magnetic
field and that what we see happen in motors etc. can be explained by
relativistic effects. Maybe this is related to this thought experiment? I
didn't get any further explanation, and I never did look into it any. Hang
on...




[from a google on:
einstein "no magnetic field"

http://www.analogzone.com/col_1028b.htm

Nobody Loves A Transformer, Part 2: Wire Again
by Brian McGinty


....it took Albert Einstein to figure them out. Stationary electrons don't
have a magnetic field. A single electron moving through empty space doesn't
have a magnetic field. Two electrons moving together, still no magnetic
field.

When electrons move relative to each other - towards each other, away from
each other, past each other - a magnetic field appears out of nowhere. In
fact, Einstein discovered the magnetic field is just the electric field as
viewed through changing frames of reference. Considered by many to be quite
a sharp guy, ...




j

 

[Sylvia Else]

operator jay wrote:

"Sylvia Else" <sylvia@not.at.this.address> wrote in message
news:4157853f$0$20129$afc38c87@news.optusnet.com.au...

I'm not disagreeing with Kevin, but there is a simple thought experiment
that shows how careful one must be about taking a theory, such as that
of James Clerk Maxwell, and attempting to use it as anything more than a
description.

Take two electrons, separated in space, stationary relative to some
observer. There's an electric field, obviously, but no magnetic field.
Now take another observer moving perpendicularly to the line joining the
electrons. This observe sees the electrons in motion. Electrons in
motion are an electric current, and an electric current produces a
magnetic field, so for that observer there is a magnetic field present.

So one observer finds a magnetic field present where another observer
finds none. The notion that a magnetic field has a concrete existence is
clearly problematic. This paradox doesn't appear in the theory itself,
because it simply tells you what will happen (or more exactly, what your
measurements will show). It doesn't say anything about what is "really"
there.

Sylvia.



I was told that Einstein showed that there is not actually any magnetic
field and that what we see happen in motors etc. can be explained by
relativistic effects. Maybe this is related to this thought experiment?

For sure, since it is exactly that relativistic model that prompted my
use of the idea in the thought experiment.

However, I wouldn't want anyone to get that idea that the field, and
resulting forces, are in some way produced by a relativistic "effect". I
make again my point that the theories only describe - they don't
explain - and they certainly don't produce effects.

Sylvia.

 

[Repeating Rifle]

in article vLOdnVlOc7ZOKMTcRVn-sw@comcast.com, Perion at
RazroRog@hotmail.com wrote on 9/28/04 12:04 PM:

"Sylvia Else" <sylvia@not.at.this.address> wrote in message
news:4157853f$0$20129$afc38c87@news.optusnet.com.au...

I'm not disagreeing with Kevin, but there is a simple thought experiment
that shows how careful one must be about taking a theory, such as that
of James Clerk Maxwell, and attempting to use it as anything more than a
description.

Take two electrons, separated in space, stationary relative to some
observer. There's an electric field, obviously, but no magnetic field.
Now take another observer moving perpendicularly to the line joining the
electrons. This observe sees the electrons in motion. Electrons in
motion are an electric current, and an electric current produces a
magnetic field, so for that observer there is a magnetic field present.

So one observer finds a magnetic field present where another observer
finds none. The notion that a magnetic field has a concrete existence is
clearly problematic. This paradox doesn't appear in the theory itself,
because it simply tells you what will happen (or more exactly, what your
measurements will show). It doesn't say anything about what is "really"
there.
And so with any motion related phenomena. Person A is on a flatbed rail car.
Just as the train passes a road crossing A tosses a tennis ball straight up to
a
height h and catches it as it comes back down. Person A calculates the
distance
the ball has traveled as 2h. Person B is stopped at the crossing watching the
train go by and sees the ball as moving through a parabolic arc. He
calculates
that the ball has moved a distance through space equal to the length of the
parabola, greater than 2h. The two observers arrive at completely different
values and describe completely different trajectory geometries. So, how far
did
the ball REALLY move through space and what was its ACTUAL trajectory? What
was
the ball's ACTUAL kinetic energy in the direction of the train's motion? A
says
zero, B says it's half the mass of the ball times the velocity of the train
squared. Either the ball has energy or doesn't - who's right. The problem is
that even notions as simple as "trajectory" or "kinetic energy" aren't
entities
in themselves but arise as part of a relationship between the motion of
observer
with observed.

Perion


Both are observing the same invariant phenomenon. Both descriptions are

correct. The Lorentz transformation can be derived by modifying Newtonian
theory the make both descriptions correct.

Bill

 

[Watson A.Name - \"Watt Su]

"Ryan Wheeler" <mojo@nospam_netscape.com> wrote in message
news:_7L5d.147268$Q7D.76117@twister01.bloor.is.net.cable.rogers.com...

Ken wrote:

Hi,

I would like to know what is a magnetic field. I mean what is it
composed of.
I searched google , asked people around me , no one seems to know.
Obviously everyone knows where how, but not what.
I thought it was electrons, but that cant be.

thank you

ken

look at this one http://www.who.int/peh-emf/en/

What I see at that URL is basically no information at all about magnetic
fields.

> search word in google is: emf

 

[Watson A.Name - \"Watt Su]

"Sylvia Else" <sylvia@not.at.this.address> wrote in message
news:4157853f$0$20129$afc38c87@news.optusnet.com.au...

Kevin Kilzer wrote:

On Sun, 26 Sep 2004 18:53:21 -0400, "Ken" <lera@sympatico.ca> wrote:


I would like to know what is a magnetic field. I mean what is it
composed
of.
I searched google , asked people around me , no one seems to know.
Obviously everyone knows where how, but not what.
I thought it was electrons, but that cant be.


Basically, both electric and magnetic fields store electromagnetic
enegy. Electric fields can be created by something as simple as a
battery, and magnetic fields come from magnets or from electrical
coils while a current flows. Why magnets make magnetic fields is a
question for quantum physics.

With respect to Sylvia, James Clerk Maxwell expressed a relationship
between electric and magnetic fields in the mid 1800's. Maxwell's
contribution was to show that a magnetic field is created as an
electric field changes, and an electric field is created as a
magnetic
field changes. The result is that if I switch an electric field off
and on, I get a magnetic field that swells and collapses with each
on-off transistion.

If I flip the swith fast enough at some frequency, I will find that
the magnetic field comes and goes with the same frequency. But,
since
a changing magnetic field will create its own electric field, the
effect moves out to this new field, which makes another magnetic
field, and so on, and that is radio.

Kevin


I'm not disagreeing with Kevin, but there is a simple thought
experiment
that shows how careful one must be about taking a theory, such as that
of James Clerk Maxwell, and attempting to use it as anything more than
a
description.

Take two electrons, separated in space, stationary relative to some
observer. There's an electric field, obviously, but no magnetic field.
Now take another observer moving perpendicularly to the line joining
the
electrons. This observe sees the electrons in motion. Electrons in
motion are an electric current, and an electric current produces a
magnetic field, so for that observer there is a magnetic field
present.

First off, electrons aren't 'stationary'. They're always moving. And
then you can't 'observe' them because the act of observing them disturbs
them. It's the old Heisenberg's Uncertainty Principle.

If you ask me, we're getting into the "Blind Men and the Elephant"
territory.

So one observer finds a magnetic field present where another observer
finds none. The notion that a magnetic field has a concrete existence
is
clearly problematic. This paradox doesn't appear in the theory itself,
because it simply tells you what will happen (or more exactly, what
your
measurements will show). It doesn't say anything about what is
"really"
there.

Sylvia.