Can magnetism exist independently of current or charge?

[MannyP2011]

Can magnetism exist independently of current or charge?
I'm just curious because the intertwining relationship between E&M.

 

[Vanadium 50]

No. If there were no electric charges, there would be no magnetic fields.

 

[MannyP2011]

I asked my professor( he has a PhD in Particle Physics) and he said magnetism can exist independently of charges but he didn't explain why during a E&M class.
I ask this because I wonder why the speculation of magnetic monopoles if magnetism is just an effect of moving charges and there are only certain ways that charges can move through space and obviously if all of the possibilities of motion must have to been exhausted since the nobel prize in the waiting if they where found.
Why do people still speculate about magnetic monopoles existing?

 

[kcdodd]

his remark probably comes from Maxwells equations, which has solutions when charge and current density is zero.

 

[Phrak]

I asked my professor( he has a PhD in Particle Physics) and he said magnetism can exist independently of charges but he didn't explain why during a E&M class.
I ask this because I wonder why the speculation of magnetic monopoles if magnetism is just an effect of moving charges and there are only certain ways that charges can move through space and obviously if all of the possibilities of motion must have to been exhausted since the nobel prize in the waiting if they where found.
Why do people still speculate about magnetic monopoles existing?

A perm. magnet can have a magnetic field without charge or current.Magnetic monopoles (or magnetic charge, really) bring a beautiful symmetry to Maxwell's equations that beg for expression. --the problem being, of course, that no one has seen any in vacuum.

Actually, I found a cheat--a classical way around it--at least in part. I'm bragging here, a little. Maxwell's equations can be formulated with complex electromagnetic potential in place of real valued potential.

A <-- A + iZ​

This would gives rise to magnetic charge. So how do we get ride of this seemingly nonphysical result? Global gauge fixing the complex phase would be sufficient.

A <-- Ae^iM is unmeasurable​

Local gauge fixing would allow magnetic charge at a distance, but at the same time, any necessarily local measurement of magnetic charge or current would return a null result.By the way, in the nonclassical world Dirac monopoles are connected by Dirac strings. Results from recent research in solid state physics seems to have measured effects attributable to Dirac strings. The background space, in this case, is not the vacuum of course, though I wouldn't be surprised if strings will be measured sometime soon between media separated in space with opposite magnetic charge associated with the separated media.

 

[Vanadium 50]

A perm. magnet can have a magnetic field without charge or current.

The magnetization arises from the electrons in the atom. If you got rid of electric charge you would also get rid of this permanent magnetization.

I don't dispute that people can write down a theory other than Classical Electrodynamics that permits different solutions (although I didn't follow yours). But that's not the focus of a forum called "Classical Physics".

 

[Phrak]

Vanadium, I don't disagree with you. When someone says that someone says magnetism can exist without charge, we may not be getting the whole context.

Except the bit about Dirac strings, I was speaking classically.

 

[Meir Achuz]

The magnetization arises from the electrons in the atom. If you got rid of electric charge you would also get rid of this permanent magnetization.

I don't dispute that people can write down a theory other than Classical Electrodynamics that permits different solutions (although I didn't follow yours). But that's not the focus of a forum called "Classical Physics".

Ferromagnetism is caused by the electron's magnetic moment, not its charge.

 

[Vanadium 50]

If an electron were neutral, it would have no magnetic moment.

 

[Naty1]

So magnetism exists without current, but not without charge.

 

[mburt]

A moving magnetic field can create a current, a stationary magnetic field cannot.

So to answer the question (as above), a stationary permanent magnet yields no current, but the converse is true as well. A stationary current (well, a coil with no moving electrons) yields no magnetic field.

There is a somewhat classical way to answer the question I guess

 

[kcdodd]

How do you define a moving magnetic field? A moving current?

 

[mburt]

Well an example of a moving magnetic field would be moving a permanent magnet over (or through) an electromagnetic (this would induce a current).

And by moving current, I just meant moving electrons. I stated it that way to enforce the converse statement

 

[mquirce]

The magnetism of electron mass particle, support idea that this particle is structured by two electric charge that move toward each other. It is not enough to have electric charge. neNeeded the moviment of this charge to create magnetism. This is the opinion of a layman.

 

[RedX]

Not to get overly pedantic, but it is possible for an object to have a magnetic moment without having an electric charge. Not just something like a neutron, but even the neutrino can have a magnetic moment.

Anyways, as to the OP, if you want, just add a magnetic charge and magnetic current to Maxwell's equation, and for every real problem you try to solve, there will be no magnetic charges/current around so set them equal to zero, and your beautifully symmetric Maxwell's equation reduces to the ugly ones (the ones without magnetic charge/current).

 

[mquirce]

Redx. I think that without find why electron, proton, neutron, neutrino have magnetism, the theory of particles is incomplete. Exactly your post extend the idea that all elementary particles must have structure. Sure a layman may have wrong ideas, because so is his horison, but to say that electron is a point and on the other hand to say has mass, magnetism, a infinite energy, a infinite geodesic, seems to do with thisme strange. I think that Gerlah experiment maybe has to idea.

 

[kcdodd]

So by moving magnetic field you mean a field changing strength and/or direction in time?

 

[Phrak]

If an electron were neutral, it would have no magnetic moment.

Well, maybe. A neutron has a magnetic moment. You could counter by saying that a neutron is composed of charged quarks, but this goes far afield into unknow territory. How much is orbital magnetic moment and how much is intrinsic--who knows?

However, it would be interesting to know if there are any articles that support this. The W weak force is exceptional it is the only fundamental boson with charge. That could change everything.

 

[Phrak]

If an electron were neutral, it would have no magnetic moment.

Well, maybe. A neutron has a magnetic moment. You could counter by saying that a neutron is composed of charged quarks, but this goes far afield into unknow territory. How much is orbital magnetic moment and how much is intrinsic--who knows?

However, it would be interesting to know if there are any articles that support this. The W weak force is exceptional it is the only fundamental boson with charge. That could change everything.

 

[Phrak]

If an electron were neutral, it would have no magnetic moment.

Well, maybe. A neutron has a magnetic moment. You could counter by saying that a neutron is composed of charged quarks, but this goes far afield into unknow territory. How much is orbital magnetic moment and how much is intrinsic--who knows?

However, it would be interesting to know if there are any articles that support this. The W weak force is exceptional. It is the only fundamental boson with charge. That could change everything.

 

[pallidin]

Phrak, your drinking too much coffee. You inadvertently posted the same message 3 times. :)

 

[Vanadium 50]

Well, maybe. A neutron has a magnetic moment. You could counter by saying that a neutron is composed of charged quarks, but this goes far afield into unknow territory. How much is orbital magnetic moment and how much is intrinsic--who knows

Doesn't matter. If the quarks had no charge, the magnetic moment of the neutron would be zero.

I don't understand your comment about the W; it has charge, it has a magnetic moment and it even has an electric quadrupole moment.

 

[Antiphon]

I asked my professor( he has a PhD in Particle Physics) and he said magnetism can exist independently of charges but he didn't explain why during a E&M class.
I ask this because I wonder why the speculation of magnetic monopoles if magnetism is just an effect of moving charges and there are only certain ways that charges can move through space and obviously if all of the possibilities of motion must have to been exhausted since the nobel prize in the waiting if they where found.
Why do people still speculate about magnetic monopoles existing?

Let's be precise. It takes a charge, which appears from another reference frame than the charge is in, to create a magnetic field. Once created however, it maintains an independent existence from the source.

In particle speak, if you have photons (or W/Z) you will have magnetic fields even if the charges that created them have long gone.

 

[RedX]

I don't understand your comment about the W; it has charge, it has a magnetic moment and it even has an electric quadrupole moment.

I think he's probably referring to the fact that something such as the neutrino has W⁺ + e^- self-energy, i.e., heuristically speaking, the neutrino turns into those particles and those particles recombine back to a neutrino. A magnetic field can hit the neutrino when it's one of those charged particles. The diagram of that would be much like the QED vertex correction, except the incoming and outgoing legs is a neutrino, and the internal legs would be the electron, and the internal boson between electron legs would be a W, and the external photon line can hit both the W and the electron line.

 

[Rayquesto]

I believe that Magnetism can exist independent from current because a current is formed from aligning magnetic fields which we call "magnetic Domains." Magnetism still exists, but the elctrons are all over the place. I don't know about chrage though because chrage still exists in magnetism regardless of unaligned magnetic fields.

 

[ZealScience]

Well, Gauss Law of magnetism in Maxwell's equations states that integral of magnetic flux of a closed surface is zero, or in differential form the divergence is zero. It means that magnetic monopoles don't exist, but it is just experience from former experiments, perhaps somewhere in the universe where monopoles are hiding out there.

Apart from Gauss Law, only Ampere's Law and the displacement current term is responsible for magnetic field. The two laws means only charges (current) and electric field can generate magnetism, if monopole is not a choice.

But if some day you discover monopoles, don't forget to inform Mr Nobel, he will reward you definitely.

 

[ZealScience]

I believe that Magnetism can exist independent from current because a current is formed from aligning magnetic fields which we call "magnetic Domains." Magnetism still exists, but the elctrons are all over the place. I don't know about chrage though because chrage still exists in magnetism regardless of unaligned magnetic fields.

Aren't the electrons moving fast? I think that moving electrons are generating current, though the current is not one resposible for the magnetic domains. In most cases, magnetic field is generated by magnetic moments, that's the idea from Bohr's magnetons which is quite handy in quantum mechanics. Still, I insist on magnetic monopoles, which physicists are looking for.

 

[Drakkith]

I believe that Magnetism can exist independent from current because a current is formed from aligning magnetic fields which we call "magnetic Domains." Magnetism still exists, but the elctrons are all over the place. I don't know about chrage though because chrage still exists in magnetism regardless of unaligned magnetic fields.

Magnetism cannot exist without charge. Period. Current is a flow of charges, usually electrons in a conductor. A stationary charge, in relation to an observer, is NOT creating a magnetic field EXCEPT through its intrinsic spin. In an atom the electrons are in orbitals around the nucleus, which means that the electrons are moving and thus create an additional magnetic field from that movement. The alignment of these in a permanent magnet is the source of it's magnetism.

Well, maybe. A neutron has a magnetic moment. You could counter by saying that a neutron is composed of charged quarks, but this goes far afield into unknow territory. How much is orbital magnetic moment and how much is intrinsic--who knows?

Yes, the magnetic moment is from the charged quarks in the neutron.

How do you define a moving magnetic field? A moving current?

It's not a MOVING magnetic field, it is a CHANGING magnetic field. I'm not sure what you mean by asking how do you define it.

The magnetism of electron mass particle, support idea that this particle is structured by two electric charge that move toward each other. It is not enough to have electric charge. neNeeded the moviment of this charge to create magnetism. This is the opinion of a layman

I can barely understand you, but I think you are saying we require 2 separate particles to describe electromagnetism, which isn't true.

 

[MannyP2011]

Thanks to all who replied, I'm just a second year physics major to whom half of this was out of my league. But the other half was very helpful.. thanks

 

[Rayquesto]

Magnetism cannot exist without charge. Period. Current is a flow of charges, usually electrons in a conductor. A stationary charge, in relation to an observer, is NOT creating a magnetic field EXCEPT through its intrinsic spin. In an atom the electrons are in orbitals around the nucleus, which means that the electrons are moving and thus create an additional magnetic field from that movement. The alignment of these in a permanent magnet is the source of it's magnetism.

Well, Drakkith, what is your insight as to how something contains magnetism yet doesn't contain a current or charge? I mean, if a current doesn't exist, doesn't that mean that magnetic domains don't exist, partially due to the right hand rule and the nature of directions of current and magnetic field? like the direction of the magnetic field is perpendicular to the current it produces.