If Magnetic fields are "solid" AND "UNMOVING", How can they "attract" another magnet?

[Bender]

12 hours ago, JohnMnemonic said:

QM doesn't deal with mechanics of solid objects. To use QM in such case, you would have to describe the behavior of all the particles, which create a macroscale object. It might be possible - but I won't even try...

That is the point I want to make. To describe the magnetic field caused by an electric current, QM is worthless, because there are too many particles involved. Classical models work perfectly, though.

12 hours ago, JohnMnemonic said:

Hmm, then explain me, how works a pernament magnet, without using QM.

The magnetic material has a magnetisation term added to the magnetic field strength, depending on the suscepibility. Add in a memory effect, and you have a nice hysteresis with a remanent field.

Edited February 27, 2018 by Bender

[JohnMnemonic]

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It depends what level you want to understand it. Classical theory is perfectly good enough for most everyday cases.

Well, if you want to understand something - you need to understand it as deep, as you can

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That is not really the role of physics. Physics describes how things with those properties behave. (It is possible that some future theory might explain why some of those properties exist, but there will be other unexplained things.)

But of course - physics is about discovering and understanding all the aspects of physical reality. But I see no reason, to assume, that something is beyond our understanding.

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The Lorentz transform of the electric field.

Well, a neutron has no net electric charge and has it's own magnetic moment.

Besides electron orbitals can't be considered as movement of point charges. Properties of electrons are undetermined due to the superposition

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Then this depends on your definition of explain. That light has different wavelengths and frequencies is observed. Why this is the case may require QM, but that is not a prerequisite for explaining refraction and reflection, which can be done classically.

Funny thing is, that there's not so many differences between both ways

Compare light with sound - where is the border between QM and acoustics?

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The "why" is not part of the science, though, so this lack of knowledge is not a failing of the science. 

Of course it's not... But wouldn't be nice to look for some possible solutions to this problem...?

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That is the point I want to make. To describe the magnetic field caused by an electric current, QM is worthless, because there are too many particles involved. Classical models work perfectly, though.

QM works just fine. In an electric current magnetic moment of electrons is perpendicular to the direction of current - alignment of magnetic moments creates a magnetic field

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The magnetic material has a magnetisation term added to the magnetic field strength, depending on the suscepibility. Add in a memory effect, and you have a nice hysteresis with a remanent field.

And what's the memory effect? How magnetisation affects the structure of matter? What is the smallest pernament magnet, which scientists created? QM can explain it. Alignment of magnetic moments in atom creates a magnetic field, just like the alignment of magnetic moments of star systems in a galaxy, creates a galactic magnetic field. Magnetic field is the same in micro and the macroscale...

Edited February 27, 2018 by JohnMnemonic

[swansont]

13 hours ago, JohnMnemonic said:

Well, if you want to understand something - you need to understand it as deep, as you can

Then we understand nothing, since we will inevitably reach a question that we can't answer. So this is not a particularly useful definition of understand.

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Well, a neutron has no net electric charge and has it's own magnetic moment.

Neutrons are not the only (or even a typical) source of magnetic fields.

You said "no part of physics, which would explain magnetism" and I gave an example. I only need to give one. That you can give another is irrelevant to your claim.

13 hours ago, JohnMnemonic said:

 Besides electron orbitals can't be considered as movement of point charges. Properties of electrons are undetermined due to the superposition

Angular momentum is what matters, and this is not undetermined.

 

On 2/14/2018 at 5:19 PM, JohnMnemonic said:

Moving charges = quantum stuff.

Moving charges is completely covered by classical physics. Lorentz transform the electric field, and you have the magnetic field.

[Bender]

19 hours ago, JohnMnemonic said:

QM works just fine. In an electric current magnetic moment of electrons is perpendicular to the direction of current - alignment of magnetic moments creates a magnetic field

But the magnetic field of a current is not perpendicular to the current. Your explanation makes no sense. At least the right hand rule has the direction of the magnetic field right.

Your explanation also suggests that a neutron beam produces a magnetic field similar to an electron beam, while an alpha beam produces none. That doesn't sound right.

20 hours ago, JohnMnemonic said:

And what's the memory effect? How magnetisation affects the structure of matter? What is the smallest pernament magnet, which scientists created? QM can explain it. Alignment of magnetic moments in atom creates a magnetic field, just like the alignment of magnetic moments of star systems in a galaxy, creates a galactic magnetic field. Magnetic field is the same in micro and the macroscale...

That's not what you asked. You asked me to explain a permanent magnet without QM, and I did. Moreover, my explanation is much more useful when actually using a magnet. 

[JohnMnemonic]

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Then we understand nothing, since we will inevitably reach a question that we can't answer. So this is not a particularly useful definition of understand.

Everything can be answered, if you search for the answer deep enough

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Neutrons are not the only (or even a typical) source of magnetic fields.

Generally single subatomic particles are not the source of magnetic field in macroscale. The smallest magnet was created, by combining 5 atoms

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You said "no part of physics, which would explain magnetism" and I gave an example. I only need to give one. That you can give another is irrelevant to your claim

That's because science seems to ignore the ALIGNMENT of magnetic polarities in the process of magnetic field creation...

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Angular momentum is what matters, and this is not undetermined.

But angular momentum IS undetermined in the case of an electron in an electron cloud. Not to mention, that quantum spin is not an angular momentum a mechanical understanding: electron is not a tiny, spinning ball - it's a probability distribution...

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Moving charges is completely covered by classical physics. Lorentz transform the electric field, and you have the magnetic field.

Lorenz Law doesn't describe the cause of EM induction - it just describe how, but no why it happens. Besides the border between EM and QM is VERY thin...

Is this QM or EM:

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But the magnetic field of a current is not perpendicular to the current. Your explanation makes no sense. At least the right hand rule has the direction of the magnetic field right.

But right hand rule shows, that magnetic field IS perpendicular to electric current

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Your explanation also suggests that a neutron beam produces a magnetic field similar to an electron beam, while an alpha beam produces none. That doesn't sound right.

https://en.wikipedia.org/wiki/Neutron_magnetic_moment

https://www.sciencedirect.com/science/article/pii/S0921452697005425

"The magnetic moment of the neutron allows some control of neutrons using magnetic fields, however,^[34][35] including the formation of polarized neutron beams. One technique employs the fact that cold neutrons will reflect from some magnetic materials at great efficiency when scattered at small grazing angles.^[36] The reflection preferentially selects particular spin states, thus polarizing the neutrons. Neutron magnetic mirrors and guides use this total internal reflection phenomena to control beams of slow neutrons."

I couldn't find the answer, if neutron beams produce magnetic fields through EM induction, just like electrons - but they seem to react to an external magnetic field, similar to electrons... Alpha particles have no magnetic moment - as the spins of neutrons and protons cancel eachother out...

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That's not what you asked. You asked me to explain a permanent magnet without QM, and I did. Moreover, my explanation is much more useful when actually using a magnet. 

But without explanation, terms like: "magnetisation" or "magnetic memory" have no actual meaning...

Edited March 2, 2018 by JohnMnemonic

[Bender]

21 hours ago, JohnMnemonic said:

But right hand rule shows, that magnetic field IS perpendicular to electric current

That is obviously not the right hand rule I was referring to, since the magnetic field that causes a force on the moving charge is an external field and not caused by the moving charge.

I would advice you to study classical EM theory some more before you delve deeper in QED.

 

21 hours ago, JohnMnemonic said:

But without explanation, terms like: "magnetisation" or "magnetic memory" have no actual meaning.

Sure they do. They have predictable and quantifyable effects. They are perfect to select the right magnet for an application.

21 hours ago, JohnMnemonic said:

https://en.wikipedia.org/wiki/Neutron_magnetic_moment

https://www.sciencedirect.com/science/article/pii/S0921452697005425

"The magnetic moment of the neutron allows some control of neutrons using magnetic fields, however,^[34][35] including the formation of polarized neutron beams. One technique employs the fact that cold neutrons will reflect from some magnetic materials at great efficiency when scattered at small grazing angles.^[36] The reflection preferentially selects particular spin states, thus polarizing the neutrons. Neutron magnetic mirrors and guides use this total internal reflection phenomena to control beams of slow neutrons."

I couldn't find the answer, if neutron beams produce magnetic fields through EM induction, just like electrons - but they seem to react to an external magnetic field, similar to electrons... Alpha particles have no magnetic moment - as the spins of neutrons and protons cancel eachother out...

It is not because magnetic fields have some effect on neutrons, that it is similar to the effect on charged particles, as described by the right hand rule you gave. For the effect on charged particles, classic theory suffices. For the much smaller effect on neutrons, I agree that QM is unavoidable.

But we were discussing magnetic fields caused by particles, and classic theory predicts no such fields around a neutron beam, which is at least a good approximation. Even with QM spin I don't think a non polarised neutron beam would cause a net external field, but I could be wrong.

Moving Alpha particles cause a magnetic field, but if you claim otherwise, I would like to see your evidence.

Edited March 3, 2018 by Bender

[swansont]

On 3/2/2018 at 3:58 PM, JohnMnemonic said:

 That's because science seems to ignore the ALIGNMENT of magnetic polarities in the process of magnetic field creation...

Well, no. It's required for the explanation of domains in ferromagnetic materials, so I really have no idea what you're on about.

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But angular momentum IS undetermined in the case of an electron in an electron cloud. Not to mention, that quantum spin is not an angular momentum a mechanical understanding: electron is not a tiny, spinning ball - it's a probability distribution...

You can spin polarize atoms. There are a number of experiments that depend on this ability, plus some interesting tricks to keep the spin polarization from degrading.

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Lorenz Law doesn't describe the cause of EM induction - it just describe how, but no why it happens. 

That wasn't your claim. "Magnetic field of a moving charge can be explained only with QM", which is BS.