# How does a mgnet work?

big prairie
Is there any evidence that particles are exchanged to mediate the magnetic force?

If there is how do these particles cause a one magnet to cause motion in a
particular direction for another magnet?

If there are no particles mediating this reaction how would a field line exert the
force?

What are magnetic fields made of?

Crazy Tosser
Is there any evidence that particles are exchanged to mediate the magnetic force?

No, particles are not exchanged in any way.

If there is how do these particles cause a one magnet to cause motion in a
particular direction for another magnet?

No D=

If there are no particles mediating this reaction how would a field line exert the
force?

In a raw piece of metal, domains of motion are all in disorted order. Magnet generates a magnetic field that aligns all those domains in one direction, thus forcing them to move towards the magnet.

What are magnetic fields made of?

Out of magnetic fields

Phlogistonian
Is there any evidence that particles are exchanged to mediate the magnetic force?

According to quantum electrodynamics, the magnetic force (and the electric force) is mediated by virtual photons. The theory makes very accurate predictions. See http://en.wikipedia.org/wiki/Precision_tests_of_QED

The evidence for virtual particles is indirect because an individual virtual particle cannot be observed. According to the theory, what we see are the aggregate effects of an infinite number of virtual particles. From a philosophical standpoint, one can argue that this does not really prove that virtual particles exist. And that is correct. It doesn't really prove it. But the theory works very well and will continue to be used until a better one comes along.

If there is how do these particles cause a one magnet to cause motion in a
particular direction for another magnet?

If there are no particles mediating this reaction how would a field line exert the
force?

Magnetism is a fairly complicated force. You can find a tutorial here: https://www.physicsforums.com/showthread.php?t=95523

What are magnetic fields made of?

Photons (maybe).

Phlogistonian
No, particles are not exchanged in any way.

That's the classical theory of electromagnetism. This is the quantum age. ;)

big prairie
1. Am I correct in believing that the dominantcurrent theory says that the mediator of the electromagnetic force is the virtual photon?
2. Is the transmission of virtual photons supposed to be the source of magnetic field lines?
3. How is it that virtual photons are thought to cause something to move toward something else?
4. Is it correct to say magnetic domains within a material are caused by groups of atoms that have aligned their electron spins? What is meant by saying that the electron spins are aligned?

I appreciate knowing when something is suggested by direct evidence and when it is implied by indirect evidence and when we just don't know.

Phlogistonian
1. Am I correct in believing that the dominantcurrent theory says that the mediator of the electromagnetic force is the virtual photon?

Yes.

2. Is the transmission of virtual photons supposed to be the source of magnetic field lines?

Yes. But one shouldn't think of the photons as traveling along the field lines. A virtual photon travels from one charged particle to another. The field lines are a way of representing the classical field. They are only indirectly related to the virtual photons.

3. How is it that virtual photons are thought to cause something to move toward something else?

One charged particle emits a virtual photon. Another charged particle absorbs it. In the process, the particles exchange some energy and momentum, and this causes a change in motion.

You can find a good explanation of the theory in the book "QED" by Richard Feynman.

4. Is it correct to say magnetic domains within a material are caused by groups of atoms that have aligned their electron spins?

Yes.

What is meant by saying that the electron spins are aligned?

"Spin" is the intrinsic angular momentum of the electron. The electron has some properties that are similar to what you would expect if it were a little spinning ball. (Purists will tell you that it's not really a spinning ball. It just has some properties that are like a spinning ball.) Anyway, if the spins are aligned, that just means that the electrons are spinning the same way. (Purists will tell you that's not the right way to think about it, but that's simplest way I can think of to explain it.)

Last edited:
big prairie
Phlogistonian,

I could see momentum pushing but how can it pull?

Last edited:
Phlogistonian
Phlogistonian,

I could see momentum pushing but how can it pull?

Good question. That's never been clear to me, either. I remember wondering about that, but when I learned QED, I got so bogged down in learning the details of the mathematics that I forgot about it. QED is very complicated. :yuck:

It bothers me that I don't know this, so I'll look into it, but it may take me days or weeks to figure it out. Maybe someone who understands it better can answer your question.

pallidin
Please excuse my laziness in research before asking this, but is magnetism associated only with electrons, or can other charged particles exhibit the magnetic phenomenon, such as the proton, etc...?

Phlogistonian
Please excuse my laziness in research before asking this, but is magnetism associated only with electrons, or can other charged particles exhibit the magnetic phenomenon, such as the proton, etc...?

Every charged particle with spin possesses an inherent magnetic field. And every charged particle in motion produces an additional magnetic field from the motion.