if magnetism is the result of angular momentum

[lemur]

If something is spinning, it seems logical that the momentum of its spin could be transferred to something else and that work would have to be done to effect the transfer. So if magnetism is caused by electron spin, why can't that angular momentum be transferred to something else? Also, is there a way to calculate the amount of energy in the angular momentum of a magnet, like calculating the amount of energy in a given quantity of mass?

[ajb]

I think you may want to learn about the Ising model.

[lotek1]

So I know I am a simpleton when it comes to physics, but I had an idea. My idea deals with the Hallbach array, (kind of in a circular form) and that something to that effect might be the reason for non magnetic material. the groupings of negatives and positives cancel out any kind of magnetism on the outside of the material at the atomic level. I also thought, what if that kind of goes along with string theory so that at certain speeds it stays as a circular hallbach array and once the speed increases past a certain point, it breaks into a string and moves as a wave. would that make sense as to how the electrons travel the way they do?

[ajb]

So I know I am a simpleton when it comes to physics, but I had an idea. My idea deals with the Hallbach array, (kind of in a circular form) and that something to that effect might be the reason for non magnetic material. the groupings of negatives and positives cancel out any kind of magnetism on the outside of the material at the atomic level. I also thought, what if that kind of goes along with string theory so that at certain speeds it stays as a circular hallbach array and once the speed increases past a certain point, it breaks into a string and moves as a wave. would that make sense as to how the electrons travel the way they do?

 

I don't follow how this addresses lemur's opening questions. I suggest looking at the Ising model which is a statistical model of ferromagnetism. In particular the electrons spin is fundamental in understanding magnetism.

[lotek1]

bear with me..... if you have an electron spinning, but in actuallity it is not an electron, but a representation due to the magnetization and how the negative field is what we see based on its interaction with the world around it. So the electron portrays a negative field due to its quark arrangement and not the spin. If this is true, then it is only considered an electron because of the pattern that the quarks move in. Spin, according to the laws of a gyro would only have a torque 90 deg in relation to the applied force, and it does not make sense to me why spin would determine polarity. I guess what I am saying is I don't understand how spin would cause magnetism. Again I am a simpleton. I don't profess to know much, that is why I am here on this forum to learn.

[michel123456]

If something is spinning, it seems logical that the momentum of its spin could be transferred to something else (...)

 

Stop. It does not seem logical at all. We seem to accept too easily the propagation of force from something to something else through thin air. If you refute action at a distance, you understand nothing. As I do.

 

 

edited

Edited February 19, 2011 by michel123456

[swansont]

bear with me..... if you have an electron spinning, but in actuallity it is not an electron, but a representation due to the magnetization and how the negative field is what we see based on its interaction with the world around it. So the electron portrays a negative field due to its quark arrangement and not the spin. If this is true, then it is only considered an electron because of the pattern that the quarks move in. Spin, according to the laws of a gyro would only have a torque 90 deg in relation to the applied force, and it does not make sense to me why spin would determine polarity. I guess what I am saying is I don't understand how spin would cause magnetism. Again I am a simpleton. I don't profess to know much, that is why I am here on this forum to learn.

 

!

Moderator Note

Electrons are not comprised of quarks. Any followup on that part of your posts should go in a different thread

 

Classically, any charge that is on a spinning sphere would generate a magnetic field, and the direction of the spin determines it polarity. QM spin is an analogue to that. Something with a charge and angular momentum should have a magnetic moment.

 

Stop. It does not seem logical at all. We seem to accept too easily the propagation of force from something to something else through thin air. If you refute action at a distance, you understand nothing. As I do.

 

 

"Not seem logical" here is a personal observation. As such it really isn't an argument against anything. There is no guarantee that any concept will be understandable, much less easily understandable, to anyone. That doesn't make the concept wrong, or even illogical.

 

 

———

 

As to the OP, there isn't any energy "in" angular momentum. Both are properties of a system. The Ising model ajb mentions is a model of flipping (electron) spins, but a in ferromagnet that's not really an option, because you have fixed the atoms in a lattice. Such a magnet can transfer angular momentum, but it will have to be because you can rotate the magnet, or are exerting a torque on it.

[lemur]

Stop. It does not seem logical at all. We seem to accept too easily the propagation of force from something to something else through thin air. If you refute action at a distance, you understand nothing. As I do.

Who said anything about refuting action at a distance? How else would electrons and protons interact with each other? Far from seeking refutation, I am trying to better understand it by asking question that may turn out to be ludicrous, but at least have the potential to enlighten me as to what exactly makes them ludicrous. I'm thinking this question may boil down to the dynamics of electron-repulsion in terms of spin-to-spin. It seems that magnetism results in alignment of new iron electrons because of some asymmetry in the rotating field. Then it would also seem like this asymmetry doesn't so much allow for some kind of traction where angular momentum is transferred mechanically as it allows the contours of varying attraction and repulsion to harmonize vis-a-vis one another. Am I off in a wrong direction with this? If this is somewhat sensible, my question becomes whether the spins would have to harmonize in a way that compliment each other, i.e. by positive-strong areas in the field attracting to negative-strong areas in the field and then spinning in a way that minimizes same-charge repulsion.

 

the direction of the spin determines it polarity.

Meaning that the poles of the axis of rotations correspond to positive and negative magnetic poles, such as how the Earth's magnetic poles roughly correspond to its axis of rotation?

 

"Not seem logical" here is a personal observation. As such it really isn't an argument against anything. There is no guarantee that any concept will be understandable, much less easily understandable, to anyone. That doesn't make the concept wrong, or even illogical.

I think my wording was taken as some kind of insistence that something must be so because it "seems logical that . . ." The only reason I mentioned this was to contextualize the question of why or why not angular momentum at the atomic level can or can't transfer its momentum in the form of work. The "seeming logical" comment was as much a set-up for falsifying my application of logic as it was an invitation to consider the logic of momentum transfer in the context of angular momentum in terms of magnetism.

 

 

As to the OP, there isn't any energy "in" angular momentum. Both are properties of a system. The Ising model ajb mentions is a model of flipping (electron) spins, but a in ferromagnet that's not really an option, because you have fixed the atoms in a lattice. Such a magnet can transfer angular momentum, but it will have to be because you can rotate the magnet, or are exerting a torque on it.

How can there not be ANY energy? There must be SOME, however minute. Admittedly, if the electrons are already a circulating wave and then that pattern of circulation is spinning, which is what I understand by spin, then it would be odd to say that the total energy of the wave is greater because it is circulating in a slightly different macro-pattern. However, if momentum-transfer can happen as electric current goes through a wire, and perform work as a result, why wouldn't a current circulating at the level of the atom also have the potential to do work? Or maybe that is what photon-emission is.

 

I'm going to start a related thread because I have been thinking about another angle comparing magnetic polarity and ionization, but I don't want to convolute this thread more than it already is.

 

 

[Oldman]

The motion of a mass 'creates' angular monentum at a distance from an axis. This is very similar to the fact that the motion of a charge creates magnetic field (with N-S polarity) at a distance from an axis.

Both can be brought to be similar with a slight adjustment in the related vector products without any loss of physics.

In the following all symbols are vectors.

Angular monentum (moment of monentum): Lm = r x p.

Angular current (moment of current): Le = r x i.

Here p is lienar momentum vector; i the current vector.

 

I have completed a table of similarities, which I cannot discuss because of the Forum's rules.

 

Isn't Nature so simple and simlar?

[michel123456]

Who said anything about refuting action at a distance? (...)

 

Isaac Newton (about gravity).

"It is inconceivable that inanimate brute matter should, without the mediation of something else which is not material, operate upon and affect other matter, without mutual contact, as it must do if gravitation in the sense of Epicurus be essential and inherent in it. And this is one reason why I desired you would not ascribe 'innate gravity' to me. That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance, through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it." I.Newton, 1692, 3rd letter to Bentley. (emphasis mine)

[lemur]

Isaac Newton (about gravity).

"It is inconceivable that inanimate brute matter should, without the mediation of something else which is not material, operate upon and affect other matter, without mutual contact, as it must do if gravitation in the sense of Epicurus be essential and inherent in it. And this is one reason why I desired you would not ascribe 'innate gravity' to me. That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance, through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it." I.Newton, 1692, 3rd letter to Bentley. (emphasis mine)

This is an interesting issue, but I'm not sure why you're raising it in this thread. I suppose it has to do with the problem of electrons acting on each other without direct contact? But what basis is there for electrons or matter generally to "make contact" except through force-interactions between interacting fields? What is matter except atoms consisting of nuclear particles and electrons that attract and repel each other? How can you call it "action at a distance" when the electrons of two particles collide, bounce off each other, and transfer momentum? This reminds me of another thought I had relating to this thread, which is whether the shape of electrons in different levels could allow them to transfer angular momentum? For example, if an electron is "ballooned out" on either side of the nucleus, wouldn't its angular momentum propel the sides of the "dumbbell" like hammers that would transfer that momentum to other "hammer shaped" electrons by more direct collision?

[swansont]

How can there not be ANY energy? There must be SOME, however minute. Admittedly, if the electrons are already a circulating wave and then that pattern of circulation is spinning, which is what I understand by spin, then it would be odd to say that the total energy of the wave is greater because it is circulating in a slightly different macro-pattern. However, if momentum-transfer can happen as electric current goes through a wire, and perform work as a result, why wouldn't a current circulating at the level of the atom also have the potential to do work? Or maybe that is what photon-emission is.

 

 

I didn't say there wasn't any energy, I said there isn't any energy "in" angular momentum. You can have energy without having any angular momentum at all. They are separate concepts.

 

 

I have completed a table of similarities, which I cannot discuss because of the Forum's rules.

 

(Emphasis added)

 

?

 

Isaac Newton (about gravity).

"It is inconceivable that inanimate brute matter should, without the mediation of something else which is not material, operate upon and affect other matter, without mutual contact, as it must do if gravitation in the sense of Epicurus be essential and inherent in it. And this is one reason why I desired you would not ascribe 'innate gravity' to me. That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance, through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it." I.Newton, 1692, 3rd letter to Bentley. (emphasis mine)

 

You've been here long enough to know that argument from authority carries no weight, and that physics has advanced some since 1692.

[lemur]

I didn't say there wasn't any energy, I said there isn't any energy "in" angular momentum. You can have energy without having any angular momentum at all. They are separate concepts.

Was I not specific enough about the kind of energy I was referring to? I was referring to energy that would transfer from being angular momentum of the electron in question to being some other form of energy/work. There would be conservation of energy in that the spin would be reduced as an equal amount of energy transferred to another medium. Another way to put it might be to ask whether spin reflects an increase in the energy of the electrons' motion or just a change in the pattern of that motion?

[swansont]

You can't transform angular momentum into energy. CAN'T. It's not energy. A system with angular momentum will ALSO have energy, and that is what can be transferred.

 

The spin of an electron is quantized, and the magnitude of it cannot be changed. It is a spin - 1/2 particle. It always has 1/2 hbar of angular momentum.

[lemur]

You can't transform angular momentum into energy. CAN'T. It's not energy. A system with angular momentum will ALSO have energy, and that is what can be transferred.

Isn't any form of momentum an expression of the energy put into accelerating the moving object to its given speed? Does that not apply to angular momentum of atomic electrons?

 

The spin of an electron is quantized, and the magnitude of it cannot be changed. It is a spin - 1/2 particle. It always has 1/2 hbar of angular momentum.

So it either spins or it doesn't; and when it goes from spinning to not, does it lose energy and if so, how much? Where does/can the energy go? Likewise, when a magnet heats up enough for its spins to go out of alignment, does that involve a release of energy that was stored in the spin-alignment as frozen by the lattice?

[Cap'n Refsmmat]

So it either spins or it doesn't; and when it goes from spinning to not, does it lose energy and if so, how much? Where does/can the energy go? Likewise, when a magnet heats up enough for its spins to go out of alignment, does that involve a release of energy that was stored in the spin-alignment as frozen by the lattice?

I think you misinterpreted. Either it spins or it spins. Electrons always have [imath]\frac{1}{2} \hbar[/imath] spin angular momentum.

[lemur]

I think you misinterpreted. Either it spins or it spins. Electrons always have [imath]\frac{1}{2} \hbar[/imath] spin angular momentum.

So what does the spin do, then, besides create a "magnetic moment?" Does it change directions due to interaction with other particles? If so, does the direction-change involve inertial resistance?

 

 

 

[mississippichem]

So what does the spin do, then, besides create a "magnetic moment?" Does it change directions due to interaction with other particles? If so, does the direction-change involve inertial resistance?

 

It causes further splitting of the already quantized energy levels. Without it, the Pauli Exclusion principle wouldn't hold. Much chemistry is governed by the pairing and spin rules of fermions, namely electrons.

Edited February 20, 2011 by mississippichem

[DrRocket]

If something is spinning, it seems logical that the momentum of its spin could be transferred to something else and that work would have to be done to effect the transfer. So if magnetism is caused by electron spin, why can't that angular momentum be transferred to something else? Also, is there a way to calculate the amount of energy in the angular momentum of a magnet, like calculating the amount of energy in a given quantity of mass?

 

 

http://en.wikipedia.org/wiki/Einstein%E2%80%93de_Haas_effect

[lemur]

http://en.wikipedia....3de_Haas_effect

From reading that article, I can't see how anything about the physicality of the spin is proven as claimed. But maybe I'm misunderstanding the experiment. The magnet is suspended inside the coil and when electric current is used to create a rotating magnetic field in the coil, the magnet spins along with it? Then somehow another magnetic field is detected within the spinning ferromagnet that spins in the opposite direction as the magnet itself? And that shows that angular momentum is conserved?

 

I think I'm understanding it wrong because I would just think the electric current generates a magnetic field and that pulls the ferromagnet along with it, the way compasses turn if you turn a magnet near them. But this experiment seems to be reporting some magnetic field other than an alignment between the electric-current and the suspended magnet?

 

 

[Moontanman]

Is the property of spin the same thing as a spinning top or a spinning ball? I though the property of "spin" was a way to describe something that has no real world counterpart like "Color" and "Charm" when dealing with sub atomic particles.

[DrRocket]

From reading that article, I can't see how anything about the physicality of the spin is proven as claimed. But maybe I'm misunderstanding the experiment. The magnet is suspended inside the coil and when electric current is used to create a rotating magnetic field in the coil, the magnet spins along with it? Then somehow another magnetic field is detected within the spinning ferromagnet that spins in the opposite direction as the magnet itself? And that shows that angular momentum is conserved?

 

I think I'm understanding it wrong because I would just think the electric current generates a magnetic field and that pulls the ferromagnet along with it, the way compasses turn if you turn a magnet near them. But this experiment seems to be reporting some magnetic field other than an alignment between the electric-current and the suspended magnet?

 

 

 

We must be reading different articles.

 

In simple terms they took a cylinder of iron (a ferromagnetic material) hit it with a pulse magnetic field to align the magnetic domains (think atoms) in the cylinder and it started rotating. To conserve angular momentum something inside the cylinder must be rotating in the opposite direction. That something is related tp "spin".

 

What is also interesting is that Einstein actually did an experiment.

Edited February 20, 2011 by DrRocket

[lemur]

In simple terms they took a cylinder of iron (a ferromagnetic material) hit it with a pulse magnetic field to align the magnetic domains (think atoms) in the cylinder and it started rotating. To conserve angular momentum something inside the cylinder must be rotating in the opposite direction. That something is related tp "spin".

So the iron cylinder was not a permanent magnet? Then the coil around did what exactly to magnetize it (e.g. was it just a conductor with a current going through it?)? Then as the current went through it, the iron cylinder rotated because the magnetic field generated by the coil was rotating? So I still don't get what shows that there was something else spinning counterdirectionally within the iron cylinder?

 

What is also interesting is that Einstein actually did an experiment.

What do you mean? I thought Einstein flew around in spaceships looking at clocks through telescopes and built nuclear power plants? I thought Einstein was to physics what Indiana Jones was to archaeology.

 

 

[swansont]

Is the property of spin the same thing as a spinning top or a spinning ball? I though the property of "spin" was a way to describe something that has no real world counterpart like "Color" and "Charm" when dealing with sub atomic particles.

 

Same property (angular momentum). The "unphysical" part is that the electron is so small that it cannot be physically spinning sphere with a charge distribution— you would need to exceed the speed of light, and the fact that it is quantized.

[michel123456]

I thought the electron was something like a cloud.