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Does a magnetic field have mass?

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Does the magnetic field of a wire carrying a current have mass?

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The field has energy, and thus it would have mass. But the field does not exist independent of that which generates it.

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6 minutes ago, swansont said:

The field has energy, and thus it would have mass. But the field does not exist independent of that which generates it.

When you say ‘would have mass’ this sounds uncertain? 

An emp exists independently of its source.

When a magnetic field permeates a pemeable substance, does the permeable substance increase in mass? I’m guessing probably not.

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We expect that the field has a mass (that is, mass-energy). I however understand that this was not yet observationally confirmed, at least not by a direct observation, due to technical difficulties.

47 minutes ago, swansont said:

But the field does not exist independent of that which generates it.

This is not my view. Even the fact that the field is a voluminous object (spreads away from the thing that is 'generating' it) requires it to exist independently.

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1 hour ago, MPMin said:

When you say ‘would have mass’ this sounds uncertain? 

It does?

1 hour ago, MPMin said:

An emp exists independently of its source.

You said “magnetic field of a wire carrying a current” not EMP

1 hour ago, MPMin said:

When a magnetic field permeates a pemeable substance, does the permeable substance increase in mass? I’m guessing probably not.

Once you have interactions it becomes difficult to separate the source.

Similarly, e.g. the mass of hydrogen is less than the mass of proton + electron. But you can’t say that the mass came from one particle or the other. It’s one system.

Energy is conserved, however. That will tell you what happens to the mass.

1 hour ago, Danijel Gorupec said:

This is not my view. Even the fact that the field is a voluminous object (spreads away from the thing that is 'generating' it) requires it to exist independently.

You can produce a magnetic field of a wire carrying a current without the wire and current?

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17 hours ago, MPMin said:

When you say ‘would have mass’ this sounds uncertain? 

E = mc2 (So energy can be treated, in some cases, as mass. For example, most of the mass of an atom is the energy binding the quarks together in the nucleons.)

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22 hours ago, swansont said:
23 hours ago, MPMin said:

When you say ‘would have mass’ this sounds uncertain? 

It does?

Yes it does sound uncertain when you choose to say ‘would’. This makes it sound expected rather than known. Is it a known? 

22 hours ago, swansont said:

You can produce a magnetic field of a wire carrying a current without the wire and current?

Yes, the magnetic field will briefly exist around the wire just after the current stops 

6 hours ago, Strange said:

E = mc2 (So energy can be treated, in some cases, as mass. For example, most of the mass of an atom is the energy binding the quarks together in the nucleons.)

But this equation means thane by when energy is energy it isn’t mass and visa versa. If the mass of an atom is mostly energy, which part of atom experiences gravitational force?  

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1 hour ago, MPMin said:

Yes it does sound uncertain when you choose to say ‘would’. This makes it sound expected rather than known. Is it a known? 

As I said in the post, you can’t separate the field from the source. So it’s a hypothetical, based on a division that you can’t make and can’t directly measure.

1 hour ago, MPMin said:

Yes, the magnetic field will briefly exist around the wire just after the current stops 

That’s not the same field, as it will change in time and also generating an electric field. It’s also not in the spirit of the question that was asked.

 

1 hour ago, MPMin said:

But this equation means thane by when energy is energy it isn’t mass and visa versa.

No. Mass is a form of energy. All mass is energy. Not all energy is mass (kinetic energy)

1 hour ago, MPMin said:

If the mass of an atom is mostly energy, which part of atom experiences gravitational force?  

The whole thing.

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3 hours ago, MPMin said:

But this equation means thane by when energy is energy it isn’t mass and visa versa. 

No it doesn’t. It just means you can relate mass and energy in that way. 

Quote

If the mass of an atom is mostly energy, which part of atom experiences gravitational force?  

All of the atom, obviously. 

Not sure what/why you are asking this...

Maybe worth noting that mass does not appear in the equations of GR, only energy (and a few other things like momentum, pressure, etc)

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12 hours ago, Strange said:
Quote

If the mass of an atom is mostly energy, which part of atom experiences gravitational force?  

All of the atom, obviously. 

What’s obvious about this when generally speaking matter is what is attracted to gravity. Are you saying that the energy of the atom is attracted to gravity as well the matter of the atom, or are you saying that at the atomic scale there is no matter as such it’s just energy acting as matter? Because the next thing I’m going to ask is when a wire carries a current and produces a magnetic field around itself (energy) does the wire’s attraction to gravity increase (or its mass increase) due to the additional energy around the wire? 

In other words if gravity can attract energy then a wire carrying a current should weigh more then when it’s not carrying a current. 

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22 minutes ago, MPMin said:

What’s obvious about this when generally speaking matter is what is attracted to gravity. Are you saying that the energy of the atom is attracted to gravity as well the matter of the atom

Pretty much, yes. It is energy that is the cause of gravity, mass is just one form of that. 

23 minutes ago, MPMin said:

or are you saying that at the atomic scale there is no matter as such it’s just energy acting as matter?

I would say that atoms are matter (and have mass). Below the atomic scale, it is less clear. The word “matter” is not really well defined at that point. 

25 minutes ago, MPMin said:

Because the next thing I’m going to ask is when a wire carries a current and produces a magnetic field around itself (energy) does the wire’s attraction to gravity increase (or its mass increase) due to the additional energy around the wire? 

I would say no, because the field is outside the wire so it does not increase the effective mass of the wire. (Although any heating of the wire, for example, would increase its mass - by a minute amount)

27 minutes ago, MPMin said:

In other words if gravity can attract energy then a wire carrying a current should weigh more then when it’s not carrying a current. 

If there is extra energy in the wire associated with that current (which there may be - have never thought about this before) then yes. 

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3 hours ago, MPMin said:

What’s obvious about this when generally speaking matter is what is attracted to gravity.

I probably shouldn't have said "obvious" (I have tried to avoid that ever since reading The Zen of Mortorcycle Maintenance about 35 years ago!)

I thought about this a bit more. Nearly all of the mass of the atom is in the nucleus (and nearly all of that mass is due to the binding energy of the quarks). So it is mainly the nucleus that is attracted by gravity. But the atom is so tightly bound that the whole thing behaves as a single thing under the (relatively weak) force of gravity.

 

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4 hours ago, MPMin said:

What’s obvious about this when generally speaking matter is what is attracted to gravity. Are you saying that the energy of the atom is attracted to gravity as well the matter of the atom, or are you saying that at the atomic scale there is no matter as such it’s just energy acting as matter? Because the next thing I’m going to ask is when a wire carries a current and produces a magnetic field around itself (energy) does the wire’s attraction to gravity increase (or its mass increase) due to the additional energy around the wire? 

In other words if gravity can attract energy then a wire carrying a current should weigh more then when it’s not carrying a current. 

“Attraction to gravity” is an awkward phrase. Things are attracted by gravity. They are attracted to the source of gravity.

The mass of a system depends on its energy content. If the source of the current’s energy is external to the system, then the wire and field increase in mass. The electrons have increased KE internal to the wire (but not COM KE) and the field has energy.

If you put the whole thing in a magnetically-shielded box, you would see no increase in mass of the box + contents. ( heat loss would result in a decrease in mass)

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On 8/31/2019 at 8:31 AM, MPMin said:

Does the magnetic field of a wire carrying a current have mass?

The photon is the force carrier of the magnetic field in quantum mechanics.  Photons don't have a measurable amount of mass, but one could argue that they have energy, therefore they have mass.  I am not sure it has actually ever been proven, directly by experiment, that photons are the force carrier of the magnetic field, either...

Edited by Conjurer

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25 minutes ago, Conjurer said:

I am not sure it has actually ever been proven, directly by experiment, that photons are the force carrier of the magnetic field, either...

That is a bit like saying that the magnetic field isn't what's responsible for magnetism.

It doesn't have to be proved(*); it is part of the definition of the photon. But, of course, the model (quantum electrodynamics) has been extensively tested and shown to be correct.

(*) Nothing is ever proved in science.

 

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42 minutes ago, Strange said:

That is a bit like saying that the magnetic field isn't what's responsible for magnetism.

It doesn't have to be proved(*); it is part of the definition of the photon. But, of course, the model (quantum electrodynamics) has been extensively tested and shown to be correct.

(*) Nothing is ever proved in science.

 

I just don't see why it would be so difficult to prove, or why it would be a complete waste of time.  The photon should be the easiest particle to detect with modern technology.  It doesn't make much sense in electrical engineering, and most experts in quantum mechanics will say what you said.  Then they have no idea how this could be applied to EE.

In EE, the electric field is only used to increase/decrease a voltage or create a current.  Then this only occurs in the presence of another electromagnetic field or coil.  The rest of the circuit carrying electrons will remain unchanged.  Then any electron should be capable of absorbing any photon.

 

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You might want to study what a vector gauge boson entails. (Virtual boson) Did you ever stop to think why all the experts in quantum mechanics will tell you the same thing ?

 There is a difference between the photon as per a quanta of light and the photon as per the mediator of an EM field. VP's have less than a quanta of energy/mass. 

Here is a quick run down of the virtual photon

https://en.m.wikipedia.org/wiki/Virtual_particle

The part on the Feymann diagrams where it mentions the internal lines this is where the VP operate. They are not observable due to their mass/energy being too low. Even with an idealized perfect detector it would be impossible to detect individual VP. Though we can detect their collective effects.

The external lines on Feymann diagrams however have an excess of a quanta of action. They are observable under measurement. Yes I know it's a lot to take in but the quantum theories take a considerable study to get a handle on the topic. Though relativity is also a lengthy topic to learn. You will come across a lot of theories which will be difficult to apply in a strictly classical understanding. In some cases there is no classical means to explain.

Edited by Mordred

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8 hours ago, Conjurer said:

I just don't see why it would be so difficult to prove, or why it would be a complete waste of time. 

Nothing is ever proved. But the fact that photons are the force carriers for the electromagnetic field is confirmed everyday. So I don’t know what you are looking for. 

8 hours ago, Conjurer said:

The photon should be the easiest particle to detect with modern technology. 

Yep. Your eyes do it all the time. 

8 hours ago, Conjurer said:

In EE, the electric field is only used to increase/decrease a voltage or create a current. 

Not really. 

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10 hours ago, Conjurer said:

I just don't see why it would be so difficult to prove, or why it would be a complete waste of time. 

QED is one of the best-established theories in physics. 

10 hours ago, Conjurer said:

The photon should be the easiest particle to detect with modern technology.  It doesn't make much sense in electrical engineering, and most experts in quantum mechanics will say what you said.  Then they have no idea how this could be applied to EE.

Virtual photons can't be detected directly. They can be inferred owing to the success of the model built on them.

 

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On 9/2/2019 at 3:17 AM, swansont said:
Quote

Yes, the magnetic field will briefly exist around the wire just after the current stops 

That’s not the same field, as it will change in time and also generating an electric field. It’s also not in the spirit of the question that was asked.

Having thought about this; its not a different field either, its a segment of the same field.

If a magnetic field around a wire doesn’t increase the mass of the wire (the wire system if you like) then can it be assumed that an emp has no mass?

Edited by MPMin

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1 minute ago, MPMin said:

Having thought about this; its not a different field either, its a segment of the same field.

If a magnetic field around a wire doesn’t increase the mass of the wire (the wire system if you like) then can it be assumed that an emp has no mass?

As I stated earlier, it depends on how you define the system.

"If the source of the current’s energy is external to the system, then the wire and field increase in mass"

The premise of your question is contrary to what I have already said.

An EMP has no mass because photons don't have mass. The static field would.

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5 minutes ago, MPMin said:

can it be assumed that an emp has no mass

An EMP consists of a mix of 
Electric field
Magnetic field
Electromagnetic radiation
Electrical conduction
None of these carry mass, but can carry momentum as far as I know.

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13 hours ago, swansont said:

An EMP has no mass because photons don't have mass. The static field would.

Perhaps this is also point in contention in its own right, is the magnetic field around a wire actually static or is it emanating? My guess is that it’s constantly emanating outward from the wire.

 

13 hours ago, Ghideon said:

None of these carry mass, but can carry momentum as far as I know.

I don’t understand how there can be momentum without mass when p=mv?  if you’re going to say p=E/c as well I’d ask you to please show me how momentum is conserved in a system that loses E out of the system? What I mean is mass is easily accounted for because doesn’t easily convert to energy but energy easily converts to other forms of energy which is why most energy systems are not 100% efficient 

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Try the full energy momentum formula when discussing the mass of the photon it has no rest mass (invariant mass). However the photon can have the variant mass or inertial mass. If  you think about solar sails this provides an application where this is used.

See here

https://en.m.wikipedia.org/wiki/Energy–momentum_relation

The problem is not realizing that mass can and does refer  to different mass terms (invariant) rest mass and (variant ) inertial mass under GR. 

See here how the mathematical proof comes about in SR 

https://www.google.com/url?sa=t&source=web&rct=j&url=https://pdfs.semanticscholar.org/7c91/d1f7979c0f0fb4348e3b00e21abc6f2ce80a.pdf&ved=2ahUKEwjUzqOgp7bkAhXGrJ4KHa54AD0QFjAAegQIBRAB&usg=AOvVaw1Y2SJGPsxC4-m5zov6Da9p

It would be far easier to understand this than understanding how all forms of energy contribute to mass via the energy/momentum stress tensor of GR. (That includes the Stress tensor for the EM field under Maxwell equations.)

Edited by Mordred

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11 minutes ago, Mordred said:

Try the full energy momentum formula when discussing the mass of the photon it has no rest mass (invariant mass). However the photon can have the variant mass or inertial mass. If  you think about solar sails this provides an application where this is used.

See here

https://en.m.wikipedia.org/wiki/Energy–momentum_relation

The problem is not realizing that mass can and does refer  to different mass terms (invariant) rest mass and (variant ) inertial mass under GR. 

See here how the mathematical proof comes about in SR 

https://www.google.com/url?sa=t&source=web&rct=j&url=https://pdfs.semanticscholar.org/7c91/d1f7979c0f0fb4348e3b00e21abc6f2ce80a.pdf&ved=2ahUKEwjUzqOgp7bkAhXGrJ4KHa54AD0QFjAAegQIBRAB&usg=AOvVaw1Y2SJGPsxC4-m5zov6Da9p

It would be far easier to understand this than understanding how all forms of energy contribute to mass via the energy/momentum stress tensor of GR. (That includes the Stress tensor for the EM field under Maxwell equations.)

Or you could just put all the mass of a system in a box and say momentum is conserved because the mass cant escape the box but can you say the same for energy?

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