Electrical current and direction of magnetic field

[rewebster]

why electrical current passing thorough (e.g. a wire) makes the magnetic field that it creates "swirl" and always in the same direction?

For me, at least, these are the kind of questions that makes (fundamental theoretical) physics interesting.

 

[rewebster]

why electrical current passing thorough (e.g. a wire) makes the magnetic field that it creates "swirl" and always in the same direction?


I was thinking about this question in another way since yesterday, and was wondering at what level of importance in fundamental theoretical physics would figuring out- what causes the "swirl" -be?

Is it not very important?--'sort of' important?

--say, on a scale from 1 to 10, where '1' is not important at all to '10' very important?

 

[OlderDan]

Are you just guessing, or you've read about it somewhere so you know it for a fact?

It is not a guess. The magnetic field produced by a moving charge depends on the velocity, the charge, and where you are in relation to the charge. Since electrons and protons have equal and opposite charges, the fields they create are equal and opposite given the same motion.

Ultimately, the direction of the magnetic field is inferred from the effect that field has on other charges. The direction of the electric field is defined to be the direction of the force on a positive charge that finds itself in that field. All charges in electric fields experience a force proportional to their own charge, and that force is independent of their state of motion.

Charges in magnetic fields experience forces that are proportionl to their own charge, but they only experience the force if they are moving. Furthermore, the force they experience depends very much on their state of motion. If they move one way, the force is in a certain direction, but if they move the opposite way the force is reversed. There are even directions the charge can move through a magnetic field where it experiences no force at all, and it experiences the maximum force when moving perpendicular to the no-force directions with a sinusiodal dependence on the angle between the direction of motion and the no-force direction. The maximum force is found to be proportianal to the magnitude of the moving charge, its speed, and the strength of the field.

All of this obseved behavior has to be incorporated into the definition of the magnetic field. The definition that incorporates all of this behavior in a self-consistent way is to define the direction of the magnetic field to be the direction in which a charge can move through the field without experiencing a force. Once this is done, the force asociated with all other directions of motion can be described in terms of the vector cross product of the velocity with the magnetic field. The symmetry argument put forth earlier by ZapperZ was correct as far as it went. It was just missing the observed effect that the field has on moving charges.

The bigger mystery is why a moving charge exerts a force on another moving charge that cannot be explained by the Coulomb force. Two charges moving parallel to one another at the same speed exert this force on one another. To an observer moving along with the charges, they are at rest. How can one observer who sees them moving see one thing and another observer who sees them at rest witness something else? You got to ask Albert E. It's all related to the relativity of space and time.

http://galileo.phys.virginia.edu/classes/252/rel_el_mag.html

 

[rewebster]

why electrical current passing thorough (e.g. a wire) makes the magnetic field that it creates "swirl" and always in the same direction?

Is it not very important?--'sort of' important?

--say, on a scale from 1 to 10, where '1' is not important at all to '10' very important?




So this isn't too important in fundamental theoretical physics, then?-


--or is it something that is just ignored (for some reason)?



Anyone?

 

[OlderDan]

why electrical current passing thorough (e.g. a wire) makes the magnetic field that it creates "swirl" and always in the same direction?

Is it not very important?--'sort of' important?

--say, on a scale from 1 to 10, where '1' is not important at all to '10' very important?




So this isn't too important in fundamental theoretical physics, then?-


--or is it something that is just ignored (for some reason)?



Anyone?

It's a 10. No doubt about it

"Maxwell's most important achievement was his extension and mathematical formulation of Michael Faraday's theories of electricity and magnetic lines of force. In his research, conducted between 1864 and 1873, Maxwell showed that a few relatively simple mathematical equations could express the behavior of electric and magnetic fields and their interrelated nature; that is, an oscillating electric charge produces an electromagnetic field. These four partial differential equations first appeared in fully developed form in Electricity and Magnetism (1873). Since known as Maxwell's equations they are one of the great achievements of 19th-century physics."

Quote from

http://www.phy.hr/~dpaar/fizicari/xmaxwell.html

 

[rewebster]

It's a 10. No doubt about it

Good--


I'm glad that at least one other person thinks that this would be important

 

[rewebster]

OlderDan--(or anyone else)

What other 'mysteries' do you rate a '10' ?

 

[rewebster]

Somewhere in there must be the explanation for the field having unidirectional "rotational sense", and for why two conductors parallel to each other carrying current in the same direction attract each other.

To me, the attractive/repulsive force is another "10" for being another 'unexplained' mystery.

Just about everywhere one can read about the 'domains' of magnets. Reading most of what I have found, the 'domains' aren't explained too well--just that they are there and that they may/probably/are? the source.


Has anyone read anything 'new' about 'domains'? --links?--the (electron?) photos of domains look like chevrons or 'tree' design

 

[LHarriger]

Are you just guessing, or you've read about it somewhere so you know it for a fact?

Viewing a hydrogen atom from the electrons stationary lab frame you could give the old argument that the fine structure splitting of the hydrogen spectra is due to the spin orbit coupling of the orbiting proton's magnetic field with the spin magnetic moment of the electron (there would not be an additional angular magnetic moment coupling since, according to the electron's frame, it is at rest.) Of course, this is a bit botchy in real life because the electron is not in an inertial frame. Nevertheless, the idea of proton induced magnetic fields is entirely valid.

 

[rewebster]

It seems most physicists are working in some very detailed areas working with some very specific field.

Are there any out there that are more 'known' to be working primarily in 'old' fundamental physics (magnetism, light, gravity,etc.)?

 

[masudr]

We often consider most of these phenomena to be entirely explained.

e.g. classical electromagnetism (which includes magnetism and light) is completely explained by Maxwell's equations. Of course, there are results that have not yet been calculated, but most believe that in principle they could be.

Gravity is thought to be understood in terms of general relativity, although there are many speculations as to how it could be modified, and there currently appear to be several phenomena that might disagree with its predictions. Hopefully some further experimental results, due in the next couple of years, can confirm or dispel or suspicions.

 

[rewebster]

We often consider most of these phenomena to be entirely explained.

e.g. classical electromagnetism (which includes magnetism and light) is completely explained by Maxwell's equations.


Oh--I agree---For all physicists working in any applied field, all the information is there. In fact, it seems to me, that all the known properties, equations, etc. have to be taken for granted in order for them to do their work. Teachers almost have to present the properties and equations also as a given to present what is known, because that is what is known. I'm not at all questioning the properties or the math. They are basically explained very, very well. What I was looking for was more fundamental. It's seems that a lot of the questions and posts deal with fundamental questions: e.g. what is magnetism? What is light? a wave, a particle, a wave/particle, or some variation? (In fact, a lot of the questions are or are nearly duplicates of a lot of past ones, and that IF a person searched the archive posts, they probably would find an question and answer, similar, if not exactly the same as what they were going to ask--it would save time and frustration). A lot of the answers deal with a 'math' solution, a properties solution (how it does 'x' when it does 'y'). Other answers seem to enter the philosophy/free will controversy often.


Gravity is thought to be understood in terms of general relativity, although there are many speculations as to how it could be modified, and there currently appear to be several phenomena that might disagree with its predictions. Hopefully some further experimental results, due in the next couple of years, can confirm or dispel or suspicions.

The answers from those giving them seem to be arranged to their own specialty and/or interest area (relativity, QFT, direct application, etc.), but the answers usually include qualifiers (it's 'x' when it does 'y', but it's not 'x' when it does 'z'), and some answers will come back 'it is unknown'.

That's why I was wondering if there was anyone who was still considering themselves (or who knew anyone) as a basic theoretical fundamental physicist?---(that still considered the fundamental problems unresolved.) It seems that most have had to find niches that search for something unique to a certain aspect of some certain theory (e.g. entanglement). It just seems that there should be some (one) out there more 'known' to still be questioning the whole field of 'unknowns' and to be 'known' for his/her enthusiasm of doing so---maybe there isn't?

 

[masudr]

Physics produces models. It does not, and never purported to, answer "what is?" questions: that's metaphysics.

 

[rewebster]

masudr--

I had worked on a reply about 'metaphysics' and the 'what is..?' for about a half an hour---

---went back to one of the earlier pages to double check something


--and lost the reply as it didn't get 'kept'---oh well

I have to do 'something' (non-metaphysical) but I'll repost something later

 

[masudr]

I see.

There are definitely unresolved problems in fundamental theoretical physics. But the point is that until we have some very definite experimental evidence to compare with, we will have a very tough time coming up with a new theory.

As it stands, Lorentz-invariant QM (with all the gauge invariances of the 3 non-grav. interactions) and GR explains a huge body of phenomena. But some people are out there, looking to answer questions like, "But where does that cosmological constant come from?"

 

[rewebster]

Physics produces models. It does not, and never purported to, answer "what is?" questions: that's metaphysics.

When I think of metaphysics, it tends to be more toward the spiritual, or conversations of the essence of 'things'. There seems to be posts and debates and conversations in just about every one of the forums on all levels, including some, on what could easily be called 'metaphysical'. I don't personally think they should be banned at all, or restricted in a lot of ways (JIMHO). I think they should be encouraged, as long as they stay on or near the topic.

This is because just about every story you read or hear about the very initial concepts of ideas, the thoughts, and conversations tend toward what could be termed 'metaphysical'. One in particular that comes to mind is when Einstein was thinking and talking about light---"wondered about riding a beam of light"----IF you want to talk about something being in the area of 'metaphysics'--there it is---and where would the theories that he came up with be without this and his other 'metaphysical' thoughts that he thought about and talked to others about. (I would guess that if Einstein posted (somehow) a thread here titled, "I wonder what light would look like if I were riding on the beam?" --it may probably be 'locked' as too speculative.)

Forums are the new coffee houses that Einstein used to frequent-- (just a little more impersonal though).

From the first post:
I mean: what inside conductor's material (atoms) makes field go around that forward direction of current, and why is it ALWAYS the same direction of "swirl"? what mechanism, what logic is implied there??

You could, if you wanted to, take this as a 'metaphysical' question---so?


If you do look at a lot of the post thread titles even in the physics section of the physicsforum, you CAN interpret, if you want, them as 'metaphysical' questions. "what is magnetism?" , "reflecting light?" , "do photons...?" , etc., etc. Most questions will be answering the same, but one or two may spark a new thought--like Einstein's "riding a beam of light" asked in a different light (pun intended).

Who knows what question may spark a new line of thought.

("Answers are easy. It's asking the right questions which is hard."--D. W.---F.of E.)

That's why I was asking if there are any people (physicists) that enjoy thinking more about the fundamental aspects of physics theory. It seems that just because questions like 'what is magnetism?' is so well answered by rout (?) answers doesn't mean that a discussion may not bring up a new thought. Once in a while, I think that because, it seems, that because no one has ever answered it, that it is sometimes purposely thrown into the 'metaphysics' area as it seems to be unanswerable.

I personally think that it should be in the realm of a 'physics' question, as the question will have an answer eventually, I believe. Do you think that questions like this about the 'basics' that haven't been answered yet have to be, or should be, regarded as ' totally, completely, and absolutely unanswerable' and should be grouped with questions like, 'do people have souls?'

--------------------------------------------

If you don't want to be 'known' to have an interest in basic fundamental ideas, you can always send me a private message. I can see that some may see these types of questioning of 'basics' may seem to some as 'acknowledging' that there are still quite a few 'unknown' basic ideas, and some may not want to be known for having such an interest.

 

[rewebster]

There are definitely unresolved problems in fundamental theoretical physics. But the point is that until we have some very definite experimental evidence to compare with, we will have a very tough time coming up with a new theory.

What area/kind of very definite experimental evidence would you think that should be, or do you think it can be resolved mathematically?

 

[masudr]

By metaphysics, I usually mean about physics. While that fits in, more or less, to your interpretation of the word, it must be made clear that if any experiment can be done to produce results (whether actual experiments or thought experiments), then we move back into physics. e.g. "What if I was moving at speed c, what would I observe?" is not metaphysical.

As for the first post, it demonstrates that perhaps something fundamental is not yet understood: it is not that the conducting ions/electrons fundamentally make the magnetic field come about - we just observe this field in this situation.

As for unanswered theoretical questions requiring experimental evidence: e.g. magnetic monopoles, a setting where quantum gravity effects can be observed, scattering events where Higgs bosons should appear etc. There's a page on stuff like this in Wikipedia I think...

Edit Yes there is: http://en.wikipedia.org/wiki/Unsolved_problems_in_physics

 

[SAZAR]

I say that the strange perpendicular orientation of magnetic field compared to direction of current has to do with the SHAPE (cofiguration) of the charged particle itself.

Electron - it is composed of some basic building blocks of matter the same ones that orientate in space around the source of the magnetic field - actualy the space and the magnetic field itself.
The importance of its shape doesn't "come into light" until the particle is in motion.

I like this macro-world analogy: a bullet-like object falling from great hights - no matter how you drop it the side with more mass would be more attracted by gravitic field and it will gain its sense of dirrection (same is with electron in electric field - the side of electron that is more negatively charged will orientate toward source of the positive electric field that drives it toward itself), and then bullet just has to have some grooves so it forces air to spiral around it (the analogy with air (now regarding electron) is "space mass" of those disoriented bipolar primary building block particles of space vacuum, which because of configuration of those bipolar particles that make up the construction we call electron force vacuum particles to orientate around - and that's magnetic field). Simply put: gravity -> electric field; air -> "space particles"

Is this enough for Nobel Prize? :) ;)