Magnets

[mizzou]

How do they work?

 

[disappoint]

I believe the current (no pun intended) theory is that virtual photons are the mediator particle for the EM (electromagnetic) force.

Well it looks like you're getting a bit of misinformation down there, so I'll elaborate a bit.

You might want to look up virtual photons, and read up on them a bit. Although there is the danger that you'll run into a lot of technical jargon that you don't understand so I'll give you the rundown in layman's terms as best as I can here though.

Put on your conceptualizing hat and imagine 2 ice skaters in a skating rink facing each other. One of them has a bowling ball in his hands. He throws this bowling ball at the other skater and the other skater catches it. What happens to the skater who caught the bowling ball?

He gets pushed backward, away from the first skater. This happens because there is a transfer of energy from skater #1 to skater #2 via the bowling ball. That energy pushed him backward.

The the mediator particle I alluded to earlier is like that bowling ball. It is a virtual photon emitted by charged particles or magnets causing a transfer of energy that is translated into a force when absorbed or emitted.

 

[TecHNooB]

http://www.youtube.com/watch?v=wMFPe-DwULM

According to my E&M book, it's the change in the energy in the magnetic field due to the change in distance between a north and south pole of a pair of magnets being pulled apart that causes the force you feel as you pull apart two magnets. As far as how magnets generate the field, currents create magnetic fields. The magnetic field in a magnet comes from the magnetic dipoles in a material. Electrons move around the atoms in the material, creating a bunch of mini current loops. A highly magnetic material has a bunch of these loops aligned such that the magnetic fields build on top of each other. In addition, some materials have these current loops which are not aligned but align easily when they come in contact with a weak magnetic field and thus are more considered more magnetic. That's my 2 cents b4 the experts come in and bash me

 

[Cogman]

AFAIK (and no, I'm not an expert) it is related to the fact that every particle has a north and south magnetic pole. Every atom does as well. When the north and south poles of a large group of atoms line up, BAM, you have a magnet.

Exactly how it works, I doubt you'll get a straight answer. We don't even know how gravity works. Why does any fundamental force of the universe behave the way it does? (I haven't taken advanced theoretical physics, so if it is answered there, I apologize for my ignorance. I was under the impression that we had a bunch of theories but no answers)

 

[mizzou]

http://www.youtube.com/watch?v=wMFPe-DwULM

According to my E&M book, it's the change in the energy in the magnetic field due to the change in distance between a north and south pole of a pair of magnets being pulled apart that causes the force you feel as you pull apart two magnets. As far as how magnets generate the field, currents create magnetic fields. The magnetic field in a magnet comes from the magnetic dipoles in a material. Electrons move around the atoms in the material, creating a bunch of mini current loops. A highly magnetic material has a bunch of these loops aligned such that the magnetic fields build on top of each other. In addition, some materials have these current loops which are not aligned but align easily when they come in contact with a weak magnetic field and thus are more considered more magnetic. That's my 2 cents b4 the experts come in and bash me

ohhhh good video

 

[MJinZ]

Two objects will never "touch". Only will they repel or react and become something else.

 

[disappoint]

ohhhh good video

It's an entertaining video, as Feynman often is. But I am disappoint (he he) that he evaded the question for so long and then ends up saying he can't explain it in terms you understand. I think I put it in terms you can understand in my earlier post just fine. Let me know if you understood what I wrote or if you have any questions on it.

Some links that might be useful:
http://en.wikipedia.org/wiki/Virtual_particle

Well I can't find any good links on mediator particles right now but I will edit this post to add one if I do.

Interesting vid about Feynman diagrams, virtual particles and QED in general.
http://www.youtube.com/watch?v=i8O_yQHxQos&feature=related

 

[bwanaaa]

virtual particles...hmmmm...what does that really mean. is it the same kind of thinking that leads people to invent dark matter, dark energy, and dark flow? I need to read more. tnx for the link.

 

[Born2bwire]

virtual particles...hmmmm...what does that really mean. is it the same kind of thinking that leads people to invent dark matter, dark energy, and dark flow? I need to read more. tnx for the link.

Technoob has already posted the classical electromagnetic explanation. Materials contain microscopic loop currents which are also called magnetic moments. These magnetic moments normally point in random orientations which gives rise to no net magnetic fields. However, under the influence of an applied magnetic field, these dipoles will line up and generate secondary magnetic fields that oppose the applied field. This is how the permeability of a material works. In ferromagnets, large regions, called domains, naturally have a preferred direction for their dipoles without any applied fields. If we can induce these domains to line up and stay that way (which we can do by heating and applying a very large magnetic field), then we can create a permanent magnet since we can cause large numbers of these dipoles to line up and work together to create a magnetic field.

In quantum mechanics, we find that the atoms create these dipole moments, which were loop currents in classical electromagnetics, by two ways. The primary means is the intrinsic spin of the particles. Electrons and protons have a permanent magnetic dipole associated with them due to their "spin." It is the electron's spin that gives rise to the main magnetic field. There is also another magnetic field contribution from the electron's orbital momentum as it orbits the nucleus. These two small microscopic moments give rise to the macroscopic atomic magnetic fields.

disappoint is talking about quantum electrodynamics which discusses the nature of the electromagnetic field in terms of a relativistic quantum field theory. In QED, the basic constituents of the electromagnetic field are the scalar and vector potentials, not the electric and magnetic fields. The fields, instead, are the observables of the quantized potentials. The fields are propagated by photons and it is an easily acceptable picture for most people to view this in terms of electromagnetic waves. We state that electromagnetic waves, which are the time-varying coupled electric and magnetic fields, are propagated by photons and people can easily imagine these photons going out in space creating the fields as they go along. Eh, close enough. However, electomagnetic fields do not exist at DC. At DC, the electric and magnetic fields are completely decoupled and the question then becomes how do we mediate the electromagnetic force when there are no photons (only the waves have photons).

This is solved by the idea of virtual particles. It is important to point out that virtual particles are a mathematical tool and one should not try to glean too much physical insight from them as a result. What it comes down to is that on very small time scales, the Heisenberg Uncertainty Principle states that we will observe a very large spread of energies in the associated wavefunction. In this case, what we mean is that on very short time intervals, the electromagnetic field, or the vacuum field even if we have no sources, can have widely fluctuating energy levels. Using the equivalence principle from Relativity, we know that energy and matter are interchangeable and thus if the energy fluctuates high enough, a particle can pop out of the vacuum. However, because the energy only fluctuates over a very small time interval, this particle must quickly turn back into energy and return to the vacuum.

In short, there are "virtual" photons that pop in and out of existence over very very small time intervals. We call them virtual because they do not persist in time. These virtual photons are the mediators of the static fields.

 

[Ken g6]

Clear?

 

[Cogman]

Clear?

DAMN YOU AND YOUR FLUX!!!!!


GAhhh. Sorry, just had some flash backs of flux calculations for non-trivial objects...

 

[ModestGamer]

How do they work?

No one definatively knows how a magnet actually works. There are a great many thoeries about it however.

I'll give you my take. There is a undefined and hard to quantify 3 dimensional substrate of either energy or matter the exists in the universe. This medium allows for the creation of voids or conversly they create areas of high depression in the field.. The voids are the propertys we associate with magnetism,gravity and the Strong and weak nuclear force. all other forces represented are voids in the substrate that create certain behaviors. when rim areas around the voids reach a certain proportion they become particles. these particles then assemble into ever greate piece of matter.

still working on it. but its getting somewhere.

I am leaving out a tremendous amount of detail on how this works but it is as good as any other explination. but my account does not require bizare quantum behaviors.It also is not limited by the speed of light which magnetism seems to not care about.

 

[Born2bwire]

Clear?

Uggg... do they have to mix the integral and flux notations like that? Hell it manages to make even more confusing by obscuring the coupling of the time-varying electric and magnetic fields.

 

[Cogman]

Uggg... do they have to mix the integral and flux notations like that? Hell it manages to make even more confusing by obscuring the coupling of the time-varying electric and magnetic fields.

Flux is the amount of flow through some sort of surface (real or imaginary). The little circle on the integral indicates that it is a closed surface (IE a sphere).

It is still about taking an integral, just a complex one.

 

[Born2bwire]

Flux is the amount of flow through some sort of surface (real or imaginary). The little circle on the integral indicates that it is a closed surface (IE a sphere).

It is still about taking an integral, just a complex one.

Yeah, but the point is that you don't immediately know what flux is from the equations. It's better to keep the equations confined to fields and sources explicitly.