# B What moves in a magnetic field?

1. Jul 10, 2017

### Ozfer

So if you have a permanent magnet what is moving along the magnetic field lines? Electrons? Photons?

2. Jul 10, 2017

### Staff: Mentor

Nothing is moving along the field lines. Field lines don't even exist. They just help us visualize the magnetic field around the magnet. They're like the latitude and longitude lines on a globe or the contour lines on a topographic map that represent elevation.

3. Jul 10, 2017

### Ozfer

I don't mean the field lines themselves. What is changing in the magnetized area?

4. Jul 10, 2017

### Staff: Mentor

I'm sorry I don't understand your question. Can you elaborate a bit or give a specific example/setup?

5. Jul 10, 2017

### Ozfer

What on the atomic level is changing that causes magnets to pull?

6. Jul 10, 2017

### Staff: Mentor

Nothing. It is an inherent property of the electromagnetic force. Just like how opposite electric charges attract. Now, that doesn't mean that a magnetic field can't cause changes to the atomic structure of matter, it just means that these changes aren't the direct cause of the attraction.

7. Jul 10, 2017

### Ozfer

Does a magnet attract faster than the speed of light?

8. Jul 10, 2017

### Staff: Mentor

What does that mean? How is the speed of an attractive force measured?

9. Jul 10, 2017

### Ozfer

Okay so say a magnet was placed at a specific position A. Say 1 meter away is position B. Does the affect of the magnet or light reach position B faster.

10. Jul 10, 2017

### Staff: Mentor

Both arrive at the same time because they are the same thing - light is electromagnetic radiation, which is to say a propagating change in the electromagnetic field.

11. Jul 10, 2017

### Staff: Mentor

Well, remember that we can't just pop things into existence in real life, so the answer to questions like this may not always be meaningful. We'd have to move magnets into position from somewhere else or assemble them out of matter.

However, let's say that we have a magnet at position A, and position B is located 1 meter away. By moving the magnet we would create a change in the field. This change would propagate at light speed from point A to point B.

Does that help?

12. Jul 10, 2017

### Ozfer

So maybe I just have a problem with my understanding of the electromagnetic spectrum but how exactly does magnetism fall into that? Everything on the electromagnetic spectrum has a wavelength and I believe is photons but magnets do not?

Also does everything with a magnetic force affect everything else the same way gravity does?

and thanks for answering my questions

13. Jul 10, 2017

### Staff: Mentor

The electromagnetic spectrum refers to the range of frequencies/wavelengths of electromagnetic radiation, which are waves in the electromagnetic field. A static magnetic field is not a wave and cannot be said to have a frequency or wavelength. It wouldn't fall on the spectrum at all.

14. Jul 10, 2017

### Staff: Mentor

You are confusing us and yourself by using the words move and change in your question. Please try again. What are you really asking.

Is your question, "What is the difference between magnetic and non-magnetic materials?"

15. Jul 10, 2017

### Ozfer

What is the difference between a magnetic field from a magnet and the electromagnetic field? How do they interact?

16. Jul 10, 2017

### Staff: Mentor

The magnetic field is a manifestation of the electromagnetic field. Basically, it turns out that electric field and electric phenomena (such as the attraction of electrically charged particles) can be linked to magnetic field and magnetic phenomena (such as the attraction between magnets) in such a way as to suggest that they are actually the same thing just manifesting in a different way. For example, a moving electric charge produces a magnetic field in addition to the electric field is normally has. A moving magnet produces an electric field in addition to the magnetic field it usually has. Scientists ended up developing a handful of equations that can describe all electric and magnetic phenomena. These equations are called Maxwell's Equations and are extremely important. Everything from the circuit laws that govern computers and the wiring in your house to the behavior of plasma inside a fusion reactor can be derived from these equations.

Because a handful of equations can describe all of these different electric and magnetic phenomena, scientists choose to label them all as being manifestations of a single force, the electromagnetic force. This also requires that we unify the magnetic and electric fields into a single electromagnetic field.

17. Jul 10, 2017

### Ozfer

Since magnetism is a non-contact force and electric field is a wave of particles of energy(photons) why are these considered the same thing? They seem to both behave very differently and their definitions seem very different.

Doesn't electric field not put a force upon things while magnetism is defined as a force? It doesn't seem to be the electric field that causes the magnetic field but instead the moving of electrons in the wire.

18. Jul 10, 2017

### Staff: Mentor

The electric field is not a wave of photons, it is a type of field (which has a specific definition in science), and I just explained why the electric and magnetic fields are considered different manifestations of the same thing. They are described by the same math and can both be easily "transformed" from one to the other just by moving a particle or magnet. The basic fact that transforming one to the other requires only relative motion means that we really never find one without the other. It's just that in a stationary situation we find that either the electric or magnetic components are zero.

I don't know what you mean. Electrically charged particles feel forces. These forces can be electric, magnetic, or a combination of electric and magnetic forces. The fact that opposite charges attract each other through their electric fields is the fundamental reason why we have atoms and molecules. If they didn't, then the protons and electrons making up atoms would not bond to each other.

You are correct. Neither the electric field nor the magnetic field cause the other. Moving charges are one source of magnetic fields, but even a stationary electron has a magnetic field, despite having no motion. The magnetic field of a permanent magnet also requires no movement of charges.

19. Jul 10, 2017

### Ozfer

Sorry I meant, Since magnetism is a non-contact force and electromagnetic field is a wave of particles of energy(photons) why are these considered the same thing? Just because they can be converted doesn't make them the same. That would be like saying kinetic and potential energy is the same thing since they can be converted and where you find one you can find the other or the other is 0.

20. Jul 10, 2017

### Staff: Mentor

The EM field is not a wave of particles. It is a field. An EM wave is probably what you're thinking of, but that's a wave within the EM field. The field itself is not a wave.

They are the same thing. Or rather they are manifestations of the same thing. Both kinetic energy and potential energy are forms of energy.

21. Jul 10, 2017

### Ozfer

Okay fine I might not be phrasing it right because I don't know all the lingo but your just disagreeing with my wording instead of the concept. If we are saying all forms of energy are the same because they are energy and also magnetic fields are the same I am just going to have to disagree with that as I don't think it is true.

22. Jul 10, 2017

### Electric to be

The force caused by a magnetic field on a moving charge isn't the same thing as the magnetic (electromagnetic) field itself. You have the field, and then you have the interaction of charges with the field. That is known as the force. There is energy stored in the electromagnetic field. Energy in the electromagnetic field can be transferred to charges as kinetic energy through these interactions labeled as "force".

I wouldn't worry so much about photons until you understand these basic concepts of electromagnetism first, as photons are a whole different animal to tackle.

23. Jul 11, 2017

### Staff: Mentor

Are you talking about the fields vs waves thing, or the magnetic vs electric thing? Or both?
In any case, I don't feel that I've done so. The phrasing and the concepts typically go hand-in-hand, though admittedly not always.

Kinetic and potential energy are not the same things, but they are both classified as manifestations of energy because of how closely related they are. Similarly, electric and magnetic fields are not the same thing, but they are heavily related, so much so that we classify them under a single, unified field, the EM field. Whether we unify the two or treat them a separate fields is irrelevant, as it wouldn't change any of the math whatsoever, so it's mostly just a categorization and convenience issue.

24. Jul 13, 2017

### Staff: Mentor

Thread re-opened. I would like to remind members to keep in mind that this is a B-level thread and highly advanced explanations should not be posted here.

25. Jul 13, 2017

### tijana

EM is a wave? And photons that are carrying "light" are mass less particles? And particles can be behave as wave too? Is EM wave or not?