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drachefly
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Post by drachefly »

I would have some sharp words to say, but Saggiatore, you've said them all. Thanks.

And to repeat, where in the device explanation, flawed though it was, say that work was done on the electrons directly by magnetic forces? It didn't.
It did say there were forces that were due to permanent magnets... but those would be created in the normal manner as used in a normal generator. That is, changing magnetic fields create electrical fields!

This baseless semantic argument is completely unrelated to their massive error. To wit, it takes just as much energy to push it close as you get by letting it push you away.

So, even if Zentei were correct and electrons had no spin that was not attributable to spatial motions, it wouldn't matter -- his argument simply doesn't apply to the material at hand.
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Lord Zentei
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Post by Lord Zentei »

Il Saggiatore wrote:Except that I explained and supported my point.
You, on the other hand, started talking nonsense about static magnetic fields that do not do any work on magnetic moments:
Lord Zentei wrote:Incidentally, if we are going to pick nits, you are still mistaken: magnetic forces no work on magnetic dipoles either.
even though this is blatantly disproven by any compass needle in the world.And when I showed where you were wrong, you tried to evade the issue. Now, care to revise your statement?

<snip>

Can you explain how a compass needle, with constant magnetic moment, aligns itself parallel to the local, static, magnetic field?
Can you show this turning does not require work?
You can quit strawmanning me anytime. I never claimed that rotating a compass needle involved no work, merely that the magnetic field was not the fundamental agency responsible.
Which does not show that the magnetic moment is actually produced by a surface current.
It is clear that you missed the lecture where they explained that a correct treatment of magnetism in matter requires Quantum Mechanics.

<snip>

It is well known that a classical treament of magnetism in matter yields incorrect results (for example, Van Leeuwen's theorem proves that there is no diamagnetism in a classical treament; Ref.: Huanf, Statistical Mechanics, Ch. 7). So all your equations are pointless and avoid the issue, which is the work of a static magnetic field on a magnetic moment (hint: torque times rotation is work, whatever the origin of magnetic field and moment).
There is no doubt that the classical treatment is wanting. But even in quantum mechanics the dotproduct of the velocity and the magnetic part of the Lorentz-force vanishes for a non-relativistic particle without spin,
because the velocity components (momentum components) commute with each other.

As far as I'm aware (though I don't have the math), you may actually in quantum electrodynamics calculate the electron magnetic moment (not its spin) from the usual expression by integrating over rxJ expressed in terms of the quantized fields. This fact is not well known, but shows that one may also in quantum field theory view the magnetic moment as arising from electric currents.

The main difference between the classical and quantum treatments of magnetism lies in the inclusion of the spin of the electron, which is truly a quantum phenomenon.

I am still puzzled by your question about who does the work when the compass needle is turned towards the north. True enough there is apparently a moment of force acting on the dipole and the rate of work is the dotproduct of the moment of force with the rotation vector. But the way I understand it, is that this is only apparent, in the same way as for a falling loop in an electromagnetic field. Underneath, the true work is done by the emf that keeps the current running at the same value.
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TAX THE CHURCHES! - Lord Zentei TTC Supreme Grand Prophet

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Post by Lord Zentei »

drachefly wrote:This baseless semantic argument is completely unrelated to their massive error. To wit, it takes just as much energy to push it close as you get by letting it push you away.

So, even if Zentei were correct and electrons had no spin that was not attributable to spatial motions, it wouldn't matter -- his argument simply doesn't apply to the material at hand.
Fair enough, I seem to have misunderstood their claims. This was due to the following snippet:
They will both perform the same task, that of holding the ten kilos off the floor. The electro-magnet, however, has needed to be fuelled by electricity provided by a generator of some kind - it could be hydro, nuclear, wind, solar, coal or oil - and has cost a large amount in terms of energy. Much work (in the scientific sense) has been done to provide the constant electric current necessary to maintain its magnetic hold on the steel girder.
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TAX THE CHURCHES! - Lord Zentei TTC Supreme Grand Prophet

And the LORD said, Let there be Bosons! Yea and let there be Bosoms too!
I'd rather be the great great grandson of a demon ninja than some jackass who grew potatos. -- Covenant
Dead cows don't fart. -- CJvR
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drachefly
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Post by drachefly »

As far as I'm aware (though I don't have the math), you may actually in quantum electrodynamics calculate the electron magnetic moment (not its spin) from the usual expression by integrating over rxJ expressed in terms of the quantized fields. This fact is not well known, but shows that one may also in quantum field theory view the magnetic moment as arising from electric currents.
I fail to see how this could be if you take a state with J = 0 for all locations. Say, a stationary Hydrogen atom with n = 0.
I am still puzzled by your question about who does the work when the compass needle is turned towards the north. True enough there is apparently a moment of force acting on the dipole and the rate of work is the dotproduct of the moment of force with the rotation vector. But the way I understand it, is that this is only apparent, in the same way as for a falling loop in an electromagnetic field. Underneath, the true work is done by the emf that keeps the current running at the same value.
In a conventional magnet, all of the magnetism is from electron spin. Earth is a conventional magnet, so is the compass needle. Therefore, the spin moments of the electrons of the Earth and the needle are directly interacting, and to bring in an induced EMF is inappropriate.
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Post by Lord Zentei »

drachefly wrote:
As far as I'm aware (though I don't have the math), you may actually in quantum electrodynamics calculate the electron magnetic moment (not its spin) from the usual expression by integrating over rxJ expressed in terms of the quantized fields. This fact is not well known, but shows that one may also in quantum field theory view the magnetic moment as arising from electric currents.
I fail to see how this could be if you take a state with J = 0 for all locations. Say, a stationary Hydrogen atom with n = 0.
As I when I learned of it. Apparently, it is not possible to see it in non-relativistic QM.
I am still puzzled by your question about who does the work when the compass needle is turned towards the north. True enough there is apparently a moment of force acting on the dipole and the rate of work is the dotproduct of the moment of force with the rotation vector. But the way I understand it, is that this is only apparent, in the same way as for a falling loop in an electromagnetic field. Underneath, the true work is done by the emf that keeps the current running at the same value.
In a conventional magnet, all of the magnetism is from electron spin. Earth is a conventional magnet, so is the compass needle. Therefore, the spin moments of the electrons of the Earth and the needle are directly interacting, and to bring in an induced EMF is inappropriate.
The Earth's magnetic field is sue to currents in the Earth's molten core. The work that appears to be done by the magnetic field is done by whatever is keeping the current going. Anyway, given the above, conventional magnets can be described as the result of currents.
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TAX THE CHURCHES! - Lord Zentei TTC Supreme Grand Prophet

And the LORD said, Let there be Bosons! Yea and let there be Bosoms too!
I'd rather be the great great grandson of a demon ninja than some jackass who grew potatos. -- Covenant
Dead cows don't fart. -- CJvR
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Il Saggiatore
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Post by Il Saggiatore »

Lord Zentei wrote:
Il Saggiatore wrote:Except that I explained and supported my point.
You, on the other hand, started talking nonsense about static magnetic fields that do not do any work on magnetic moments:
Lord Zentei wrote:Incidentally, if we are going to pick nits, you are still mistaken: magnetic forces no work on magnetic dipoles either.
even though this is blatantly disproven by any compass needle in the world.And when I showed where you were wrong, you tried to evade the issue. Now, care to revise your statement?

<snip>

Can you explain how a compass needle, with constant magnetic moment, aligns itself parallel to the local, static, magnetic field?
Can you show this turning does not require work?
You can quit strawmanning me anytime. I never claimed that rotating a compass needle involved no work, merely that the magnetic field was not the fundamental agency responsible.
A compass needle has a magnetic moment.
Rotating the needle in a static magnetic field requires work, because of the interaction between the field and the magnetic moment.
The energy of the interaction depends on the orientaton between magnetic moment and field, hence a change in orientation implies a change in energy: work.
(See Feyman's Lectures on Physics, Vol. 2, chapter on vector potential.)
But you said:
Lord Zentei wrote: magnetic forces no work on magnetic dipoles either

which is contradicted by the fact that a magnetic field does work to rotate a compass needle.

Lord Zentei wrote:
Which does not show that the magnetic moment is actually produced by a surface current.
It is clear that you missed the lecture where they explained that a correct treatment of magnetism in matter requires Quantum Mechanics.

<snip>

It is well known that a classical treament of magnetism in matter yields incorrect results (for example, Van Leeuwen's theorem proves that there is no diamagnetism in a classical treament; Ref.: Huanf, Statistical Mechanics, Ch. 7). So all your equations are pointless and avoid the issue, which is the work of a static magnetic field on a magnetic moment (hint: torque times rotation is work, whatever the origin of magnetic field and moment).
There is no doubt that the classical treatment is wanting. But even in quantum mechanics the dotproduct of the velocity and the magnetic part of the Lorentz-force vanishes for a non-relativistic particle without spin,
because the velocity components (momentum components) commute with each other.
Irrelevant. I was addressing your claim that all magnetic fields and moments are the result of moving charges:
Lord Zentei wrote: I have already explained why this makes the principle universal: all magnetic forces are due to moving charges.
which is disproven by the spin of the electron.

Instead of addressing this, you tried to sidestep the issue:
Lord Zentei wrote:Electrons not only spin, they also revolve aroun their nucleus. For simplicity, let's assume that the orbit is a circle of radius R.
and you went on talking about the orbital motion and the associated magnetic moment, completely avoiding the issue of the electron spin.


Lord Zentei wrote: As far as I'm aware (though I don't have the math), you may actually in quantum electrodynamics calculate the electron magnetic moment (not its spin) from the usual expression by integrating over rxJ expressed in terms of the quantized fields. This fact is not well known, but shows that one may also in quantum field theory view the magnetic moment as arising from electric currents.
As far as I understand, the electron spin arises from symmetry properties within a quantum-relativistic treament (Dirac's theory and QED).
Having both an electric charge and a spin, the electron has an intrinsic magnetic moment.
But since, for all we know, the electron is a point-like particle, the interpretation of the intrinsic magnetic moment as the result of electric current is at best far-fetched.
Lord Zentei wrote: The main difference between the classical and quantum treatments of magnetism lies in the inclusion of the spin of the electron, which is truly a quantum phenomenon.
There is no diamagnetism in classical physics.
A classical treament has no exchange interaction between electrons, which is the origin of many types of magnetic ordering in materials.
This paper might be of interest.


Lord Zentei wrote: I am still puzzled by your question about who does the work when the compass needle is turned towards the north. True enough there is apparently a moment of force acting on the dipole...
"Apparently" ?
You have a mass that goes from a state of rest to a state of rotaion: that's an acceleration, and (Newton's second law) it is due to a torque. And you can measure the force.
How do you think the first meters worked?
Lord Zentei wrote: ... and the rate of work is the dotproduct of the moment of force with the rotation vector. But the way I understand it, is that this is only apparent, in the same way as for a falling loop in an electromagnetic field. Underneath, the true work is done by the emf that keeps the current running at the same value.
And what if you have no loop, like the electron spin?
Consider the Zeeman effect: you have a splitting in the spectral lines because the electron has a different energy depending on its orientation with respect to the magnetic field.

What happens to your loop in a static magnetic field if it can only rotate?
You said:
Lord Zentei wrote:If you think of the magnet dipole as a small current loop, with the current maintained by a battery, then the rotation will change the Earth's magnetic flux through the loop and thereby induce a back emf in the loop.
What would make your loop start rotating in the first place?

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Lord Zentei
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Post by Lord Zentei »

Il Saggiatore wrote:A compass needle has a magnetic moment.
Rotating the needle in a static magnetic field requires work, because of the interaction between the field and the magnetic moment.
The energy of the interaction depends on the orientaton between magnetic moment and field, hence a change in orientation implies a change in energy: work.
(See Feyman's Lectures on Physics, Vol. 2, chapter on vector potential.)
But you said:
Lord Zentei wrote: magnetic forces no work on magnetic dipoles either

which is contradicted by the fact that a magnetic field does work to rotate a compass needle.
Once again, my statement was that the magnetic field is not the fundamental agency responsible, not that no work is done.
Irrelevant. I was addressing your claim that all magnetic fields and moments are the result of moving charges:
Lord Zentei wrote: I have already explained why this makes the principle universal: all magnetic forces are due to moving charges.
which is disproven by the spin of the electron.

Instead of addressing this, you tried to sidestep the issue:
Lord Zentei wrote:Electrons not only spin, they also revolve aroun their nucleus. For simplicity, let's assume that the orbit is a circle of radius R.
and you went on talking about the orbital motion and the associated magnetic moment, completely avoiding the issue of the electron spin.
I was not sidestepping anything. That was an example of how a magnetic force could appear responsible for work it did not perform. I aslo added the demonstration that magnetic moments can be described with current elements.
Lord Zentei wrote:As far as I'm aware (though I don't have the math), you may actually in quantum electrodynamics calculate the electron magnetic moment (not its spin) from the usual expression by integrating over rxJ expressed in terms of the quantized fields. This fact is not well known, but shows that one may also in quantum field theory view the magnetic moment as arising from electric currents.
As far as I understand, the electron spin arises from symmetry properties within a quantum-relativistic treament (Dirac's theory and QED).
Having both an electric charge and a spin, the electron has an intrinsic magnetic moment.
But since, for all we know, the electron is a point-like particle, the interpretation of the intrinsic magnetic moment as the result of electric current is at best far-fetched.
I do not have a link to the paper or article where the proof it to be found, alas.
Lord Zentei wrote: The main difference between the classical and quantum treatments of magnetism lies in the inclusion of the spin of the electron, which is truly a quantum phenomenon.
There is no diamagnetism in classical physics.
A classical treament has no exchange interaction between electrons, which is the origin of many types of magnetic ordering in materials.
This paper might be of interest.
This is true.
Lord Zentei wrote: I am still puzzled by your question about who does the work when the compass needle is turned towards the north. True enough there is apparently a moment of force acting on the dipole...
"Apparently" ?
You have a mass that goes from a state of rest to a state of rotaion: that's an acceleration, and (Newton's second law) it is due to a torque. And you can measure the force.
How do you think the first meters worked?
Cut it out. I have already explained my position several times: I am not claiming that no work is done on the compass needle, merely that it is not the magnetic force that is the fundamental agency responsible, despite it "appearing" to be the case.
Lord Zentei wrote: ... and the rate of work is the dotproduct of the moment of force with the rotation vector. But the way I understand it, is that this is only apparent, in the same way as for a falling loop in an electromagnetic field. Underneath, the true work is done by the emf that keeps the current running at the same value.
And what if you have no loop, like the electron spin?
Consider the Zeeman effect: you have a splitting in the spectral lines because the electron has a different energy depending on its orientation with respect to the magnetic field.
Then we can invoke the proof I mentioned earlier. Though since I cannot find a link to it, I'll fold on the issue, at least for now.
What happens to your loop in a static magnetic field if it can only rotate?
You said:
Lord Zentei wrote:If you think of the magnet dipole as a small current loop, with the current maintained by a battery, then the rotation will change the Earth's magnetic flux through the loop and thereby induce a back emf in the loop.
What would make your loop start rotating in the first place?
I have not found a complete solution to that, though I imagine that it would be akin to the effect on a weight suspended on a current loop that is being partially held in a magnetic field. The force on the current carrying wire may be due to the magnetic field, but if the weight rises, battery is the agency responsible for the actual work. The magnetic field is merely the agency that redirects the horisontal force of the battery on the electrons into a vertical force on the loop. Much like a normal force redirects the pull on an oxcart into vertical motion as it is pulled uphill.
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TAX THE CHURCHES! - Lord Zentei TTC Supreme Grand Prophet

And the LORD said, Let there be Bosons! Yea and let there be Bosoms too!
I'd rather be the great great grandson of a demon ninja than some jackass who grew potatos. -- Covenant
Dead cows don't fart. -- CJvR
...and I like strudel! :mrgreen: -- Asuka
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Il Saggiatore
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Post by Il Saggiatore »

Lord Zentei wrote:
Il Saggiatore wrote:A compass needle has a magnetic moment.
Rotating the needle in a static magnetic field requires work, because of the interaction between the field and the magnetic moment.
The energy of the interaction depends on the orientaton between magnetic moment and field, hence a change in orientation implies a change in energy: work.
(See Feyman's Lectures on Physics, Vol. 2, chapter on vector potential.)
But you said:
Lord Zentei wrote: magnetic forces no work on magnetic dipoles either

which is contradicted by the fact that a magnetic field does work to rotate a compass needle.
Once again, my statement was that the magnetic field is not the fundamental agency responsible, not that no work is done.
So your "no work" was just a misunderstanding?
It does not actually mean "no work".
Following this excuse, electric fields do "no work" on electric charges as well, and the Earth's gravitational field is doing "no work" on a falling apple.

What did you say in your first post in this thread?
Ah yes:
Lord Zentei wrote:Yet another pseudoscientist who does not know the meaning of the word "work" in the physics sense. Work is about raising energy states, not maintaining an energy state, for fuck's sake.
Do you remember this?
Il Saggiatore wrote:the energy of a magnetic dipole interacting with a magnetic field is given by -µ۰B (Ref.: Feynman's Lectures on Physics, vol. 2, ch. 15 "The Vector Potential")
Lord Zentei wrote:
Irrelevant. I was addressing your claim that all magnetic fields and moments are the result of moving charges:
Lord Zentei wrote: I have already explained why this makes the principle universal: all magnetic forces are due to moving charges.
which is disproven by the spin of the electron.

Instead of addressing this, you tried to sidestep the issue:
Lord Zentei wrote:Electrons not only spin, they also revolve aroun their nucleus. For simplicity, let's assume that the orbit is a circle of radius R.
and you went on talking about the orbital motion and the associated magnetic moment, completely avoiding the issue of the electron spin.
I was not sidestepping anything. That was an example of how a magnetic force could appear responsible for work it did not perform.
The issue was the electron spin, which I brought as an example of magnetic moment which is not due to moving charges.
You avoided the issue and started talking about the orbital moment.
That was a clear attempt of evasion.
Lord Zentei wrote: I aslo added the demonstration that magnetic moments can be described with current elements.
And it was entirely irrelevant to the issue.
I brought an example of magnetic moment that cannot be modelled as due to a current, and you evaded the point.

Lord Zentei wrote:
Lord Zentei wrote:As far as I'm aware (though I don't have the math), you may actually in quantum electrodynamics calculate the electron magnetic moment (not its spin) from the usual expression by integrating over rxJ expressed in terms of the quantized fields. This fact is not well known, but shows that one may also in quantum field theory view the magnetic moment as arising from electric currents.
As far as I understand, the electron spin arises from symmetry properties within a quantum-relativistic treament (Dirac's theory and QED).
Having both an electric charge and a spin, the electron has an intrinsic magnetic moment.
But since, for all we know, the electron is a point-like particle, the interpretation of the intrinsic magnetic moment as the result of electric current is at best far-fetched.
I do not have a link to the paper or article where the proof it to be found, alas.
Proof of what?
Try this: Dirac's Nobel lecture (PDF):
P.A.M. Dirac wrote:The new variables a, which we have to introduce to get a relativistic wave equation linear in W, give rise to the spin of the electron. From the general principles of quantum mechanics one can easily deduce that these variables a give the electron a spin angular momentum of half a quantum and a magnetic moment of one Bohr magneton in the reverse direction to the angular momentum.

Lord Zentei wrote:
Lord Zentei wrote: The main difference between the classical and quantum treatments of magnetism lies in the inclusion of the spin of the electron, which is truly a quantum phenomenon.
There is no diamagnetism in classical physics.
A classical treament has no exchange interaction between electrons, which is the origin of many types of magnetic ordering in materials.
This paper might be of interest.
This is true.
Lord Zentei wrote: I am still puzzled by your question about who does the work when the compass needle is turned towards the north. True enough there is apparently a moment of force acting on the dipole...
"Apparently" ?
You have a mass that goes from a state of rest to a state of rotaion: that's an acceleration, and (Newton's second law) it is due to a torque. And you can measure the force.
How do you think the first meters worked?
Cut it out. I have already explained my position several times: I am not claiming that no work is done on the compass needle, merely that it is not the magnetic force that is the fundamental agency responsible, despite it "appearing" to be the case.
So, what if the magnetic field is produced by the current in a superconducting loop (no work necessary to maintain the current) or by the magnetic moment of an electron?

Lord Zentei wrote:
Lord Zentei wrote: ... and the rate of work is the dotproduct of the moment of force with the rotation vector. But the way I understand it, is that this is only apparent, in the same way as for a falling loop in an electromagnetic field. Underneath, the true work is done by the emf that keeps the current running at the same value.
And what if you have no loop, like the electron spin?
Consider the Zeeman effect: you have a splitting in the spectral lines because the electron has a different energy depending on its orientation with respect to the magnetic field.
Then we can invoke the proof I mentioned earlier. Though since I cannot find a link to it, I'll fold on the issue, at least for now.
What proof?

Lord Zentei wrote:
What happens to your loop in a static magnetic field if it can only rotate?
You said:
Lord Zentei wrote:If you think of the magnet dipole as a small current loop, with the current maintained by a battery, then the rotation will change the Earth's magnetic flux through the loop and thereby induce a back emf in the loop.
What would make your loop start rotating in the first place?
I have not found a complete solution to that,....
So you don't actually know how it is explained by the current theory of electromagnetism.
Simple: the interaction of the magnetic field with the magnetic moment result in a torque.

Lord Zentei wrote: ... though I imagine that it would be akin to the effect on a weight suspended on a current loop that is being partially held in a magnetic field. The force on the current carrying wire may be due to the magnetic field, but if the weight rises, battery is the agency responsible for the actual work. The magnetic field is merely the agency that redirects the horisontal force of the battery on the electrons into a vertical force on the loop. Much like a normal force redirects the pull on an oxcart into vertical motion as it is pulled uphill.
What if there is no weight, and what if the loop is a superconductor?

Where does the energy of a battery come from?
Electric fields interacting with electric charges. But if we accept your opinion that magnetic fields do "no work" on magnetic dipoles, the same is valid for electric fields interacting with electric charges.
So, where does the work come from?

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Lord Zentei
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Post by Lord Zentei »

Il Saggiatore wrote:So your "no work" was just a misunderstanding?It does not actually mean "no work".
Following this excuse, electric fields do "no work" on electric charges as well, and the Earth's gravitational field is doing "no work" on a falling apple.
Don't be daft. That does not follow at all.
Il Saggiatore wrote:The issue was the electron spin, which I brought as an example of magnetic moment which is not due to moving charges.
You avoided the issue and started talking about the orbital moment.
That was a clear attempt of evasion.
Bullshit. I may have been unclear, but I was not attempting to evade anything.

I do not have a link to the paper or article where the proof it to be found, alas.
Proof of what?
Then we can invoke the proof I mentioned earlier. Though since I cannot find a link to it, I'll fold on the issue, at least for now.
What proof?
The proof I mentioned to drachefly. That dipoles in relativistic QM can indeed be modeled as due to currents.


Cut it out. I have already explained my position several times: I am not claiming that no work is done on the compass needle, merely that it is not the magnetic force that is the fundamental agency responsible, despite it "appearing" to be the case.
So, what if the magnetic field is produced by the current in a superconducting loop (no work necessary to maintain the current) or by the magnetic moment of an electron?
You still need to work against the back emf.
Lord Zentei wrote:... though I imagine that it would be akin to the effect on a weight suspended on a current loop that is being partially held in a magnetic field. The force on the current carrying wire may be due to the magnetic field, but if the weight rises, battery is the agency responsible for the actual work. The magnetic field is merely the agency that redirects the horisontal force of the battery on the electrons into a vertical force on the loop. Much like a normal force redirects the pull on an oxcart into vertical motion as it is pulled uphill.
What if there is no weight, and what if the loop is a superconductor?
You tell me. Are you suggesting that the magnetic field does the work in such cases? Incidentally, you'll always have some weight.
Where does the energy of a battery come from?
Electric fields interacting with electric charges. But if we accept your opinion that magnetic fields do "no work" on magnetic dipoles, the same is valid for electric fields interacting with electric charges.
So, where does the work come from?
How the hell does that follow?
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TAX THE CHURCHES! - Lord Zentei TTC Supreme Grand Prophet

And the LORD said, Let there be Bosons! Yea and let there be Bosoms too!
I'd rather be the great great grandson of a demon ninja than some jackass who grew potatos. -- Covenant
Dead cows don't fart. -- CJvR
...and I like strudel! :mrgreen: -- Asuka
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Il Saggiatore
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Post by Il Saggiatore »

Lord Zentei wrote:
Il Saggiatore wrote:So your "no work" was just a misunderstanding?It does not actually mean "no work".
Following this excuse, electric fields do "no work" on electric charges as well, and the Earth's gravitational field is doing "no work" on a falling apple.
Don't be daft. That does not follow at all.
Magnetic, electric and gravitational interaction are all conservative forces.
If we accept that the magnetic field does no work on a magnetic dipole, then the electric field does no work on an electric charge or an electric dipole, and gravity does no work on a mass.

If "the magnetic field is not the fundamental agency responsible", what is it?

Do you remember this?
Il Saggiatore wrote: the energy of a magnetic dipole interacting with a magnetic field is given by -µ۰B (Ref.: Feynman's Lectures on Physics, vol. 2, ch. 15 "The Vector Potential")
Lord Zentei wrote:
Il Saggiatore wrote:The issue was the electron spin, which I brought as an example of magnetic moment which is not due to moving charges.
You avoided the issue and started talking about the orbital moment.
That was a clear attempt of evasion.
Bullshit. I may have been unclear, but I was not attempting to evade anything.

You are a dishonest little dipshit: in this post you started saying
Lord Zentei wrote:Electrons not only spin, they also revolve aroun their nucleus.
and from then you talked only about the orbital component of magnetic moment, without mentioning the spin once.

It is painfully obvious that you tried to evade the issue of electron spin, because it does not fit your claim that "all magnetic forces are due to moving charges".
Unless, of course, you have no clue what you are talking about and you are confusing spin and orbital components.

Lord Zentei wrote:
I do not have a link to the paper or article where the proof it to be found, alas.
Proof of what?
Then we can invoke the proof I mentioned earlier. Though since I cannot find a link to it, I'll fold on the issue, at least for now.
What proof?
The proof I mentioned to drachefly. That dipoles in relativistic QM can indeed be modeled as due to currents.
"Can be modelled": and how does that show that they are?
And can it be applied to the electron spin?

Lord Zentei wrote:
Cut it out. I have already explained my position several times: I am not claiming that no work is done on the compass needle, merely that it is not the magnetic force that is the fundamental agency responsible, despite it "appearing" to be the case.
So, what if the magnetic field is produced by the current in a superconducting loop (no work necessary to maintain the current) or by the magnetic moment of an electron?
You still need to work against the back emf.
Show us that in a superconducting loop you need to do work against the back emf.
Show us that there is a back emf when the magnetic field is produced by the spin of the electron.

Start backing up your claims.

Lord Zentei wrote:
Lord Zentei wrote:... though I imagine that it would be akin to the effect on a weight suspended on a current loop that is being partially held in a magnetic field. The force on the current carrying wire may be due to the magnetic field, but if the weight rises, battery is the agency responsible for the actual work. The magnetic field is merely the agency that redirects the horisontal force of the battery on the electrons into a vertical force on the loop. Much like a normal force redirects the pull on an oxcart into vertical motion as it is pulled uphill.
What if there is no weight, and what if the loop is a superconductor?
You tell me. Are you suggesting that the magnetic field does the work in such cases? Incidentally, you'll always have some weight.
Still trying to evade.
It is your claim and you have the burden of proof:
Il Saggiatore wrote:What happens to your loop in a static magnetic field if it can only rotate?
You said:
Lord Zentei wrote: If you think of the magnet dipole as a small current loop, with the current maintained by a battery, then the rotation will change the Earth's magnetic flux through the loop and thereby induce a back emf in the loop.
What would make your loop start rotating in the first place?
Time to answer the question (your "I imagine that it would be akin to the effect..." is not an answer).


Lord Zentei wrote:
Where does the energy of a battery come from?
Electric fields interacting with electric charges. But if we accept your opinion that magnetic fields do "no work" on magnetic dipoles, the same is valid for electric fields interacting with electric charges.
So, where does the work come from?
How the hell does that follow?
See above: if we accept that the magnetic field does no work on a magnetic dipole, then the electric field does no work on an electric charge or an electric dipole, and gravity does no work on a mass.
If the magnetic field is not the "fundamental agency", the same "reasoning" can be applied to the electric field and to the gravitational field.

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Post by Lord Zentei »

Il Saggiatore wrote:You are a dishonest little dipshit: in this post you started saying
Lord Zentei wrote:Electrons not only spin, they also revolve aroun their nucleus.
and from then you talked only about the orbital component of magnetic moment, without mentioning the spin once.

It is painfully obvious that you tried to evade the issue of electron spin, because it does not fit your claim that "all magnetic forces are due to moving charges".
Unless, of course, you have no clue what you are talking about and you are confusing spin and orbital components.
I have already clarified why I brought that up. But beleive whatever you want, Skippy.
Still trying to evade.
Still with this.

"Can be modelled": and how does that show that they are?
And can it be applied to the electron spin?
Show us that in a superconducting loop you need to do work against the back emf.
Show us that there is a back emf when the magnetic field is produced by the spin of the electron.

Start backing up your claims.
Selective reading comprehension, I see:

"Then we can invoke the proof I mentioned earlier. Though since I cannot find a link to it, I'll fold on the issue, at least for now. "
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Post by Il Saggiatore »

Lord Zentei wrote:
Il Saggiatore wrote:You are a dishonest little dipshit: in this post you started saying
Lord Zentei wrote:Electrons not only spin, they also revolve aroun their nucleus.
and from then you talked only about the orbital component of magnetic moment, without mentioning the spin once.

It is painfully obvious that you tried to evade the issue of electron spin, because it does not fit your claim that "all magnetic forces are due to moving charges".
Unless, of course, you have no clue what you are talking about and you are confusing spin and orbital components.
I have already clarified why I brought that up. But beleive whatever you want, Skippy.
Are you referring to this?
Lord Zentei wrote:That was an example of how a magnetic force could appear responsible for work it did not perform.
This has nothing to do with the electron spin, but apparently you don't think that you were avoiding the issue.
The conclusion is then that you simply don't understand what you are talking about.

Lord Zentei wrote:
Still trying to evade.
Still with this.
Of course.
You never addressed this point:
what if the magnetic field is produced by the current in a superconducting loop (no work necessary to maintain the current) or by the magnetic moment of an electron?
which is quite important if you claim that all magnetic forces originate from moving charges, or that the magnetic field does not do directly work on a magnetic dipole.

Lord Zentei wrote:
"Can be modelled": and how does that show that they are?
And can it be applied to the electron spin?
Show us that in a superconducting loop you need to do work against the back emf.
Show us that there is a back emf when the magnetic field is produced by the spin of the electron.

Start backing up your claims.
Selective reading comprehension, I see:

"Then we can invoke the proof I mentioned earlier. Though since I cannot find a link to it, I'll fold on the issue, at least for now. "
So, you cannot support your claims.

That's alright.

"This is the worst kind of discrimination. The kind against me!" - Bender (Futurama)

"Why waste time learning, when ignorance is instantaneous?" - Hobbes (Calvin and Hobbes)

"It's all about context!" - Vince Noir (The Mighty Boosh)
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