Does a magnetic field have mass?

[Conjurer]

12 hours ago, Mordred said:

the main point is that in both cases the photon number density of both the E and B fields are both represented in units of quanta, each unit of quanta is a photon so in your box the number density will depend on the frequency modes given off by the light bulb. ( though you can gain a slightly higher number via temperature which is also part of the EM spectrum.)

In a light bulb, light is given off by the excitement of the atoms and the electrons ejecting photons from their electrons in the atom.  In a magnetic field, two electrons exchange a virtual photon to create repulsion from each other.  

Don't virtual particles have a different amount of mass?  Virtual particles just link together the mathematical theory, even though they are not the same as the particle they are described as being.  That is basically the only reason why we even think they are photons.  Couldn't they be some other particle that just behaves like a photon that we cannot even detect?

[Mordred]

Each quanta represents a real photon and not a virtual photon. You are correct on the descriptive for VP in terms of mass/energy being the main property difference however those formulas above describe observable action. This is the external or real observables. All operators are observable little trick to understand QM and QFT formulas. 

Coincidentally there was a recent study posted in our News section that relates.

https://www.scienceforums.net/topic/120031-exotic-physics-phenomenon-observed/

The articles literally study the Abanarov Bohm effect and those papers show the photon polarizations with regards to the E and B fields.

 

Edited September 21, 2019 by Mordred

[swansont]

46 minutes ago, Conjurer said:

In a light bulb, light is given off by the excitement of the atoms and the electrons ejecting photons from their electrons in the atom. 

In the kind of bulb being described, it’s not excitation, which would have a discrete spectrum. The filament heats up, and we get a continuous blackbody spectrum.

[Conjurer]

6 hours ago, Mordred said:

Coincidentally there was a recent study posted in our News section that relates.

https://www.scienceforums.net/topic/120031-exotic-physics-phenomenon-observed/

The articles literally study the Abanarov Bohm effect and those papers show the photon polarizations with regards to the E and B fields.

It sounds more like they are trying to discover the arrow of time.  Photon polarizations?  Really?  I thought they had no charge.  I wouldn't be surprised if they inadvertently rediscovered that lasers generate electrons.  I know that is a discovery they have always denied to have ever occurred from what I have read about their work before.

[swansont]

10 hours ago, Conjurer said:

Photon polarizations?  Really?  I thought they had no charge.

What does one have to with the other?

 

[MPMin]

On 9/22/2019 at 3:09 AM, swansont said:

Where does the field go as it “emanates” but has reached steady-state? For a wire, the field is circular, centered on the wire? Where is the “sink”?

I’d like some clarity on this particular point.  You say the magnetic field is circular and centred around the wire while the steady direct current is flowing through the wire. If you were to take an illustrated cross section view of the wire you could say the magnetic field appears as rings around the wire, I think we are all in agreement with this description thus far.

The question is, are the rings of magnetic field stationary (fixed into position) while the steady direct current is flowing or do the rings emanate outward from the wire with new rings emerging from the wire and the outer rings get big bigger as they move away from the wire while the steady direct current is flowing through the wire? 

[swansont]

57 minutes ago, MPMin said:

I’d like some clarity on this particular point.  You say the magnetic field is circular and centred around the wire while the steady direct current is flowing through the wire. If you were to take an illustrated cross section view of the wire you could say the magnetic field appears as rings around the wire, I think we are all in agreement with this description thus far.

The question is, are the rings of magnetic field stationary (fixed into position) while the steady direct current is flowing or do the rings emanate outward from the wire with new rings emerging from the wire and the outer rings get big bigger as they move away from the wire while the steady direct current is flowing through the wire? 

No, that’s not the question if we are discussing a static field. What you are describing is the transient, after the current is started.

[MPMin]

22 hours ago, swansont said:

No, that’s not the question if we are discussing a static field. What you are describing is the transient, after the current is started.

Ive always been discussing magnetic field after the current is started as there isn’t one before the current is started. 

[studiot]

7 minutes ago, MPMin said:

Ive always been discussing magnetic field after the current is started as there isn’t one before the current is started. 

[Strange]

13 minutes ago, MPMin said:

Ive always been discussing magnetic field after the current is started as there isn’t one before the current is started. 

I will assume you are not being deliberately obtuse...

When the current starts, you have a changing current and therefore a changing magnetic field. Within a very short time you have a static current and therefore a static magnetic field.

That static case is the only condition that is relevant to your scenario, because you are talking about an extended period of time.

There will, of course, be a short electromagnetic pulse associated with the initial change in current. Depending on how perfect your reflector is, that all either be trapped in the box (meaning no loss of mass) or will escape (taking away a tiny amount of energy and therefore reducing the mass).

I still don't know wy you are inventing ever more complex scenarios instead of just understanding what you are told.

[MPMin]

I’m 

38 minutes ago, Strange said:

I will assume you are not being deliberately obtuse...

When the current starts, you have a changing current and therefore a changing magnetic field. Within a very short time you have a static current and therefore a static magnetic field.

That static case is the only condition that is relevant to your scenario, because you are talking about an extended period of time.

There will, of course, be a short electromagnetic pulse associated with the initial change in current. Depending on how perfect your reflector is, that all either be trapped in the box (meaning no loss of mass) or will escape (taking away a tiny amount of energy and therefore reducing the mass).

I still don't know wy you are inventing ever more complex scenarios instead of just understanding what you are told.

I’m not being deliberately obtuse (I can’t help the way I’m sitting) and what reading isn’t clear to me. 

Im struggling to understand what is meant by static magnetic field. 

Static means stationary, constant means unchanging. 

You have can have a constant current but a static current doesn’t make sense because anything that flows or moves isn’t stationary or static. 

By static magnetic field do you mean a snap shot in time perhaps? Probably not but I thought I’d check just in case. 

While the constant direct current is flowing it produces a constant magnetic field around the wire, the current is constant, the magnetic field is constant and if the wire was a filament then the photons emitted would be constant too. 

With a constant direct current in a filament wire, Is the magnetic field being constantly emitted outward from the filament wire at the same speed and same consistency as the photons being emitted or not? 

[Strange]

1 minute ago, MPMin said:

Im struggling to understand what is meant by static magnetic field. 

If you prefer the word "unchanging" then an unchanging current will result in an unchanging magnetic field.

Quote

You have can have a constant current but a static current doesn’t make sense because anything that flows or moves isn’t stationary or static. 

That is why the word "constant", rather than "static",  is used for an unchanging current.

2 minutes ago, MPMin said:

By static magnetic field do you mean a snap shot in time perhaps?

No. Just unchanging, unmoving. Static.

4 minutes ago, MPMin said:

With a constant direct current in a filament wire, Is the magnetic field being constantly emitted outward from the filament wire at the same speed and same consistency as the photons being emitted or not? 

No. The field is static, unchanging and unmoving.  Nothing is being emitted.

 

[MPMin]

5 minutes ago, Strange said:

No. The field is static, unchanging and unmoving.  Nothing is being emitted.

 

Not even photons? 

[Strange]

2 minutes ago, MPMin said:

Not even photons? 

Sigh.

It is a light bulb. Of course photons are emitted. You were asking about the magnetic field.

Is it time to shut this thread? Your question has been answered repeatedly but you just keep asking the same thing over and over.

[MPMin]

Then how does the unmoving magnetic field populate the space around the wire if it’s an unmoving magnetic field? 

[Strange]

3 minutes ago, MPMin said:

Then how does the unmoving magnetic field populate the space around the wire if it’s an unmoving magnetic field? 

What?

We are talking about a constant, unchanging current when the constant unchanging field is already there.

Why do you keep asking the same thing over and over and over and over and over ...

Maybe you should start reading the answers ?

[MPMin]

I’m clearly missing something that must be obvious to you all but not me.

How can a magnetic field be emitted from the wire at the commencement of the current and then stop moving while the current is still flowing? Just like the photons being constantly emitted while the current is flowing so too must the magnetic field be constantly emitted. 

This must be why you said a static magnetic field doesn’t carry away any energy? 

 

[iNow]

21 minutes ago, Strange said:

Is it time to shut this thread? Your question has been answered repeatedly but you just keep asking the same thing over and over.

If you’ll permit my opinion, yes. About 130 posts ago...

[Strange]

5 minutes ago, MPMin said:

How can a magnetic field be emitted from the wire at the commencement of the current and then stop moving while the current is still flowing? Just like the photons being constantly emitted while the current is flowing so too must the magnetic field be constantly emitted. 

How? Because they are different things.

A field is (roughly) a set of values at each spatial position. When a particular current is flowing, it will create a field that has higher values (depending on the current level) near the wire and decreasing values as you move away. If the current doesn't change then neither will the field values. There is no "flow". The field values are just what they are. There is an energy associated with the field, but like the field it is static, not radiating away.

Light is radiation. This means it is a flow of energy (electromagnetic waves or photons, depending how you want to model it) away from the source. If you were to look at any point around the light, you would have light waves / photons passing by (and carrying energy away).

5 minutes ago, MPMin said:

This must be why you said a static magnetic field doesn’t carry away any energy? 

Yes.

[MPMin]

Thank you for your detailed explanation. 

[Strange]

The other thing here is that you comparing almost completely unrelated phenomena. 

The light from the bulb is not electromagnetic radiation caused directly by the current (that would require a changing current). It is a side effect of the resistance of the wire to current flow, and is caused by this heating the wire.

If you wanted to compare the magnetic field with electromagnetic radiation generated by the current, then you would have to compare a static, DC, current (which creates a static magnetic field) with a changing, AC, current that generates a changing magnetic (and electric) field and therefore electromagnetic radiation.

I suggest you go and re-read about Faraday's experiments and what he discovered about the relationship between current, magnetic fields, chaining currents, changing fields, etc.

Maybe after the discussions here, you might see things there in a new light (excuse the pun) and get some fresh insight.

[swansont]

14 hours ago, MPMin said:

Ive always been discussing magnetic field after the current is started as there isn’t one before the current is started. 

But there isn't always a transient. It reaches steady-state. Everyone else in the thread who has mentioned this have been clear that these are two different scenarios, and I have pointed out I have been discussing the static field implied in your OP.

The non-static field propagates. No surprise, as it's the EMP, which is photons. It's not the magnetic field one calculates when one refers to a current-carrying wire with a constant current.

12 hours ago, MPMin said:

 With a constant direct current in a filament wire, Is the magnetic field being constantly emitted outward from the filament wire at the same speed and same consistency as the photons being emitted or not? 

No. The field does not move.

12 hours ago, MPMin said:

Then how does the unmoving magnetic field populate the space around the wire if it’s an unmoving magnetic field? 

 

In the region d around the wire, the field will be unchanging after a time T = d/c. That's the propagation time of the transient (the EMP)

By talking about the field of a current-carrying wire, you have implicitly chosen the time AFTER T

You can't discuss both the transient and the static case. They must be treated separately. Pick one.

 

12 hours ago, MPMin said:

I’m clearly missing something that must be obvious to you all but not me.

How can a magnetic field be emitted from the wire at the commencement of the current and then stop moving while the current is still flowing? Just like the photons being constantly emitted while the current is flowing so too must the magnetic field be constantly emitted. 

It doesn't. The EMP is not the magnetic field. They are not the same thing. This has been pointed out only about twenty times so far.

 

[studiot]

On 9/23/2019 at 11:54 PM, MPMin said:

I’m not being deliberately obtuse (I can’t help the way I’m sitting) and what reading isn’t clear to me. 

Im struggling to understand what is meant by static magnetic field. 

I sympathise.

You would not have this difficulty if folks would use the terminology that is in all my electrical engineering texts.

 

 

On 9/4/2019 at 12:23 PM, studiot said:

Again the term is steady not static.

'Static' magnetic fields have a special meaning relating to machinery, to distinguish between moving parts.

All magnetic fields are generated by moving charges, even those in permanent magnets which have steady fields.

 

(Rotating) Electric machinery operates due to the interaction of two magnetic fields (along with some conductors).

One of those fields is generated in the "stator" which strangely enough does not move (rotate)

This is therefore rightly called a static magnetic field.

The other field is generated in  - guess what - the rotor, which rotates, rotating its magnetic field with it.

This is called the rotating magnetic field.

However either or both those fields may be the result of electric current and pulsating if AC.

That is the field is not constant in time at any given point in space.

But the pattern of pulsing repeats endlessly.

So the current and field is called steady.

Note you cannot usefully use the word constant  with AC since the average value of AC is zero so a phrase like "the AC current is on average constant" is worthless.

 

Edited September 25, 2019 by studiot

[Strange]

14 minutes ago, studiot said:

You would not have this difficulty if folks would use the terminology that is in all my electrical engineering texts.

Maybe you should create a post with a list of words and their definitions that we all have to use. 

14 minutes ago, studiot said:

(Rotating) Electric machinery operates due to the interaction of two magnetic fields (along with some conductors).

The thread is not about rotating electric machinery so please don't take it off topic.

14 minutes ago, studiot said:

Note you cannot usefully use the word constant  with AC since the average value of AC is zero so a phrase like "the AC current is on average constant" is worthless.

I'm sure you have heard of RMS and if someone referred to a "constant AC voltage" then that is what I would assume they meant. But I'm sure you will tell me I am wrong. And that's fine.

[MPMin]

 

On 9/24/2019 at 12:38 PM, swansont said:

It doesn't. The EMP is not the magnetic field. They are not the same thing. This has been pointed out only about twenty times so far.

As I understand it, a magnetic field can be created by running a current through a wire and an emp can be created by pulsing a current through a wire. Aside from the duration of time between the two I don’t see any other differences. 

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

An electromagnetic pulse (EMP), also sometimes called a transient electromagnetic disturbance, is a short burst of electromagneticenergy. Such a pulse's origin may be a natural occurrence or man-made and can occur as a radiated, electric, or magnetic fieldor a conducted electric current, depending on the source.

If your view that an emp is different to a magnetic field because an emp is a segment of a magnetic field then I can see how you see them as different things an emp is a segment of a magnetic field. 

Here is another view. In the scenario of a wire carrying a current, before the current commences let’s assume there is nothing around the wire. When the current commences, wether the current is an alternating current or direct current, at the commencement of the current a magnetic field will populate the space around the wire starting at the wire and moving outwards from the wire at the speed of light. 

A direct current will produce a magnetic that doesn’t induce a current in a stationary wire but if you push the wire through that magnetic field then it will induce a current in the wire being pushed. However, On the other hand, the magnetic field from an alternating current will induce an alternating current in a stationary wire in that magnetic field. A current restive to the motion will be induced in either case the, it’s only what’s moving that is the difference. In the direct current’s magnetic field the wire has to move to induce a current and in the alternating current’s magnetic field the it’s the magnetic field that’s moving which leads me to the following analogy. 

If you consider a cross section view of the wire carrying an alternating current it could be viewed as dropping pebbles (to represent an alternating current) in to a pond from the top down view, where the pebbles impact the water represents the wire and the ripples represent the changing magnetic field emanating outwards from the wire. Considering that before the current commences there is nothing around the wire, but when the current commences the magnetic field be it from a dc or ac current will emanate from outward from the wire at the speed of light. In this analogy though, the water molecules are the magnetic field and the energy passing through the water molecules can be seen as the ripples. The water molecules do not move away from the centre but the water molecules do oscillate as the energy passes through them. In this analogy the magnetic field is basically a medium to carry energy. In a dc current the water would remain flat. So I can see why you say the magnetic field from a dc current doesn’t carry away any energy. 

Could this mean that a magnetic field from an alternating current has mass but a magnetic field from a dc current does not have mass?

appogies for the font size difference I don’t know how to change the font size in this text. [FIXED]

Edited September 26, 2019 by Strange
Fixed font size