Unnecessary magnetic poles ?

[Fairfield]

Unnecessary "magnetic poles" ?

If I run steady, same direction, currents through two close, slack parallel wires, I will see the two wires attract each other. If I reverse one of the currents I will see the two wires repel each other.

If I now roll the wires up into coils, and place them on the same axis near to each other, and again run steady, same direction, currents through them, I will again see them attract each other. But the textbooks will tell me that, in the case of the coils, it is the magnetic north and south poles of the two coils which are attracting each other instead of just their parallel currents.

Likewise, if I rotate one of the coils end for end, which causes its current to now be running opposite to that of the other coil, I will see the two coils repel each other. But the textbooks will tell me that the two coils are repelling each other because their like magnetic poles (north - north or south - south) are repelling each other, instead of their opposite parallel currents doing it.

Doesn't Occam's razor suggest that we should forget the primitive, unnecessary, concept of north and south poles around current carrying coils, and, instead, acknowledge only the direct, lateral, attraction or repulsion between parallel current carrying wires, even when they are in the shape of coils?

 

[Jonathan]

I could be wrong, but I think you got all the repel and attract parts in reference to the current wrong. I think parallel currents repel and antiparallel currents attract.

 

[chroot]

Originally posted by Fairfield
Doesn't Occam's razor suggest that we should forget the primitive, unnecessary, concept of north and south poles around current carrying coils, and, instead, acknowledge only the direct, lateral, attraction or repulsion between parallel current carrying wires, even when they are in the shape of coils?

Well, currents DON'T attract or repel each other. What's going on in one wire doesn't directly affect the other. What happens is that a current through a wire sets up a magnetic field, and this field affects electrons in the other wire by pulling them to the side. The net result of lots of electrons being pulled to the side is that the wires attract or repel each other.

The field around a straight wire is composed of concentric lines of magnetic field, so there really is no way to establish a "north" versus a "south" pole for that field -- just as there would not be in a magnetized donut of metal, in which the field lines never leave the surface.

- Warren

 

[Fairfield]

Originally posted by chroot

The field around a straight wire is composed of concentric lines of magnetic field, ...

- Warren

If the reality of that statement were unchallengeable, then, of course, I would have to accept your explanation. But it is exactly those alleged concentric magnetic lines of force that I am questioning.

The concept of a concentric magnetic field around a direct current carrying wire was established by noting the action of any magnetic compass needle brought into the vicinity of any direct current carrying wire.

But a compass needle is simply a miniature equivalent of a direct current carrying coil mounted horizontally on a pivot half way along its length, and having very flexible power leads to it.

The current on the side of this coil (or a magnetic compass needle) which is going in the same direction as a direct current in a nearby reference wire will be attracted toward that reference wire. The coil's wires carrying current traveling in the opposite direction to that of the reference wire's current will be repelled from the reference wire.

These two LATERAL forces will cause the coil (or a magnetic compass needle) to rotate to maximize these two responses, causing the coil (or a magnetic compass needle) to point across the axis of the straight direct current carrying reference wire. But this pointing direction is obviously not the direction of the actual forces which are operating on the turnable coil (or on a magnetic compass needle).

The magnetic compass needle was originally given north and south pole names because it (like an easily turnable direct current coil would) tends to turn so its ends point toward the geographical north and south poles of the Earth in response to the equatorial direct current in that giant current carrying "coil" called earth.

So, although the north and south poles of a magnetic compass needle are a useful concept for navigation purposes, I don't see where there is any real thing called north and south magnetic lines of force. I only see real lines of force at 90 degrees to the axis of what's called north and south poles.

 

[chroot]

Originally posted by Fairfield
I don't see where there is any real thing called north and south magnetic lines of force.

There isn't. It's a convention.

I only see real lines of force at 90 degrees to the axis of what's called north and south poles.

At one end of a magnet, the lines of force go into the magnet body. At the other, the lines of force leave it. The two ends of a bar magnet obviously do different things to a compass needle, so they deserve two different names. The choice of north and south is arbitrary -- call them "slargbast" and "meedle" if you like.

- Warren

 

[Albrecht]

At one end of a magnet, the lines of force go into the magnet body.

Don't forget that the magnetic lines of force are nothing different than a picture we build for ourselves, to handle a magnetic field in practice. There is no correspondence in theory because magnetism is not a force by itself but only a relativistic side effect of the electric field.

So, if we want to understand a magnetic situation really, we have to look to the electric situation and then take into account the limited velocity c by which field changes are propagated, and the relativistic contraction of a moving chain of electric charges.

 

[turin]

The magnetic version of Gauss's Law in Maxwell's equations is usually called the law of "no magnetic monopoles." If you believe that Maxwell's equations are absolute (that, in fact, there are "no magnetic monopoles"), then it certainly seems that the fundamental interaction is between currents, and that referring to the magnetic force in terms of the attraction and repulsion of poles isn't a fundamental treatment. Physics certainly seems to support this view for the most part. However, this introduces an asymmetry between the Farady tensor and its dual. I think most physicists would like for nature to be symmetric. There have been several treatments of electromagnetic theory including the existence of magnetic monopoles, which, consequently, would be attracted or repelled by the magnetic field directly. Analogously, moving magnetic monopoles (magnetic current densities) would create a transverse electric field, thus provinding a symmetry between the Farady tensor and its dual. Of course, I could talk all this nonsense (or maybe it's not nonsense) for hours; the fact of the matter remains that magnetic monopoles have not been observed. This lack of observation has been so pronounced as to warrent a law of physics that basically says "there is no such thing as a magnetic monopole."

In light of the evidence, I must concede to your argument that magnetic poles do not directly attract or repel, but that electric currents are what truly attract or repel.

 

[arcnets]

Fairfield,
your question 'Is the concept of magnetic poles unnecessary?' looks very interesting to me.
Well, IMO the standard answer is, of course, "A scientific concept is necessary as long as we need it to explain the observations".

I tell you why I find this so interesting: Because I have to teach this stuff at school. And usually, the students who I teach it to, start off with almost no knowledge on magnetism.

My idea is: 'Poles' are necessary when the course starts. But we make them unnecessary as the course proceeds. Like this:

1) Some minerals found in the Earth can attract objects made of iron, nickel, or cobalt. We call this 'magnetism' after the mines of Magnesia where these minerals were found in ancient times.

2) If we examine one of these stones, we find that there are certain areas where the effect occurs, and others where it doesn't. The active areas are called 'magnetic poles'.

3) If we take a thin long steel needle, and rub it repeatedly against a magnetic stone's pole in one direction, over its entire length, then the needle becomes magnetic with two poles at its ends.

4) If we have two such needles, then we find that their poles may attract or repel each other. Thus, there must be two different types of poles.

5) If we let such a needle swim on a cork (as the Chinese did ~1000 years ago), we find it will align roughly in geographical north-south direction. The pole pointing north is called the north pole, the other south. The instrument is called a compass and helps in navigation.

6) (LAW OF MAGNETIC POLES). Equal poles repel. Opposite poles attract.
Thus, the Earth must have a strong magnetic north pole in the south, and vice versa.

7) Today, we have much stronger magnets than the needle (I won't tell you how they're made). Their magnetism is much stronger than the Earth's, when you're close to such a magnet.

8) Such a strong magnet can hold up an iron nail. From the bottom of the nail, we can hang down another nail. And another... You see, a piece of iron that is close to a magnet, becomes a magnet itself. This even works at a distance. This is called magnetic influence (Just think of 'influenza'...). Obvioulsly, since the nails are oblong objects, they take on two poles, just like the needle. We can tell where each nail has which pole.

9) We cover a magnet with a transparent foil, and scatter iron filings onto it. They align in lines (showing the effect of magnetic influence around the magnet, since the filings are oblong objects). These lines are called magnetic field lines. Which make up the magnetic field produced by the magnet. We define the direction of a line to be 'away from the north pole'. That's just a convention. We note that each line that leaves the magnet, also enters it again.

10) We place a piece of iron close to the magnet, and then examine the magnetic field by using iron filings. We see that the field goes right through the iron, which seems to compress the lines. We know that the iron takes on influenced north and south poles. We deduce that a 'south pole' is nothing else than converging field lines going into a body, and a 'north pole' is nothing else than diverging lines going out of it. We also deduce that a field line has no beginning and no end, but goes thru any body.

11) We observe the fields of two magnets. Firstly, when they attract each other, and secondly, when they repel. We see that field lines cannot cross each other. We also see that all magnetic forces can perfectly be explained from the...

(drum roll)
LAWS OF THE MAGNETIC FIELD:
1) Magnetic field lines have no beginning and no end.
2) The north pole of a magnet is just the area where the field lines leave it. The south pole is where they enter it.
3) Field lines tend to be as short as possible (attraction).
4) Field lines tend to be as far away from each other as possible (repulsion).
5) The last 2 rules explain all magnetic forces.
6) Magnetic materials like iron compress the field lines.

(Of course, at this point you should also have told the students some facts about the internal structure of ferromagnetic materials, to explain why we can magnetize the steel permanently... but that uses poles and is not important here...)

12) Once you have these laws, you can switch on the electricity. Oersted's result is something we just have to accept, the interaction of 2 wires follows easily from the above. Even electromagnets, the Lorentz force and electromagnetic induction are easy to explain once you have introduced the LAWS OF THE MAGNETIC FIELD, which indeed make the conept of poles unneccessary. Via induction and Lorentz force, you enter the domain of special relativity...

Enough for now.

 

[turin]

Originally posted by arcnets
3) Field lines tend to be as short as possible (attraction).
4) Field lines tend to be as far away from each other as possible (repulsion).

I like this.

 

[arcnets]

turin,
I'm glad you like this. That you like this, even though you said:

Originally posted by turin
that electric currents are what truly attract or repel.

... which is of course the deeper physical principle behind all this.
But at school level, I think my concept is a good one.

Or are you being cynical? No, I guess you're not...

 

[turin]

I was being sincere. I totally agree with your perspective on teaching, especially science. IMO, for instance, students should learn about the aether before they learn that it is invalid. Why not, since they learn Newton's law for gravity, with which even he himself was uncomfortable. Science seems to start with what is readily observable, and then, if warranted by deeper investigation, the theory is adjusted. This is a development process which seems to have been robbed from students in the modern education system, and has ultimately led to great confusion in certain areas earning them the distinction of being "counterintuitive." It is one of my pet-peeves for someone to say that relativity is so.

 

[Fairfield]

I can understand that, as a commonly encountered secondary phenomenon of circular currents (requiring at least 4 parallel currents to demonstrate any magnetic effects), magnetism needs the nomenclature that is commonly attributed to it.

But I am troubled because this secondary phenomenon is always treated as the most primary phenomenon wherever there are magnetic effects occurring.

But even where there is not a truly magnetic effect occurring, this false concept gets extrapolated backward thusly. Any DC current carrying wire is claimed, on account of the action of any nearby magnetic compass, to have magnetic lines of, something, circling the wire. But the compass needle is being influenced by strictly lateral forces acting on it, as any DC coil in the same situation would be. But because the compass needle already has names on its ends, from its use for navigation purposes, we declare, without any rational reason that I can see, that there are north - south magnetic lines of, something, circling the wire. Isn't science supposed to be more critical than that?

 

[turin]

Charge is not a scalar quantity. There is a four vector that is a current density. The timelike part of this four vector is basically responsible for the electric field. The spacelike part is basically what is responsible for the magnetic field. From what I have gathered so far in my studies, the components of the magnetic field are just as real as the components of the electric field, but they are situated in the Farady tensor so that you don't see their effect on the timelike part of the current density; you see their effect on the spacelike part.

 

[Fairfield]

I still feel inclined to ask, what if Oersted had had, instead of a compass placed near his experimental current carrying wire, a pivotal tubular coil which was also carrying current? How would he have explained the turning action of the coil in that situation other than I have explained it above, as strictly, and only, as 2 lateral forces in operation.

The length of the coil would point to absolutely nothing in particular that exists in nature. Only to something that exists in the imagination due to reckless backward extrapolation from the interaction of two DC current carrying coils, or the impproper interpretation of the forces at work on a compass needle.

The true forces at work on the above coil would be more visually
indicated if the coil had no axial length at all but, instead, was just one loop with a wide oval shape.

I'll re mention that I don't see where you can even have the commonly characterized magnetic phenomena without having at least 4 parallel currents present, 2 in one direction and 2 in the opposite direction. To me this means magnetism is only a secondary, situational phenomenon which merely combines the lateral force vectors so that they appear to be coming from between the wires (and therefore around them), when they really aren't.

 

[krab]

Originally posted by Fairfield
Doesn't Occam's razor suggest that we should forget the primitive, unnecessary, concept of north and south poles around current carrying coils, and, instead, acknowledge only the direct, lateral, attraction or repulsion between parallel current carrying wires, even when they are in the shape of coils?

What you are proposing is viable, but does not really make for a simpler description. Two current-carrying coils, some distance apart are most easily described as two magnetic dipoles. The forces they exert on each other is much more easily found from formulas describing dipoles, than by integrating the currents through the (possibly very many) turns of wire in each coil.

I suppose one of the reasons many of the presentations in textbooks are based on "poles" is that elementary particles themselves appear to be point dipoles instead of current loops.

 

[Fairfield]

I understand the practicality of dealing with magnetism "as it is", but science is also supposed to concern itself with discerning the ultimate substructures of the presentations of nature in order to better understand them, explain them, and use them.

 

[Hurkyl]

But because the compass needle already has names on its ends, from its use for navigation purposes, we declare, without any rational reason that I can see, that there are north - south magnetic lines of, something, circling the wire. Isn't science supposed to be more critical than that?

It's the same reason the electric charge is positive for a proton and negative for an electron; a name was needed for the two opposite polarities.

 

[QuantumNet]

The magnetical field is a relativistic effect, it's not a part of the classical physics. What's wrong with poles?

 

[arcnets]

Originally posted by QuantumNet
What's wrong with poles?

Well for one thing, I've never seen an exact definition of 'magnetic pole'. Maybe it's the point of a magnetic body's surface where the magnetism is strongest, or where the force is at right angles with the surface... but then you got to define 'body' and 'surface' which may lead to trouble.

Yes it's a relativistic effect. Please let me babble some more about teaching physics: My personal concept is sort of 'the other way round': Introducing relativity via magnetism!

How?

- We can easily show in experiment that a moving electron in a magnetic field experiences a force, called the Lorentz force. The important thing is, a stationary electron doesn't.

- Electromagnetic induction in a moving coil can easily be explained by the Lorentz force.

- Now, surprisingly (or not) this also works with a stationary coil and moving magnet. Now, do we have a Lorentz force affecting stationary electrons? - Of course not.

- If we think about it, it's the same situation, only in another frame of reference. Thus: "Physical laws are the same in each frame of reference". Furthermore: "Only relative motion counts. Absolute motion does not count, since absolute motion cannot be defined anyway".

- As a consequence: The term 'moving electron' makes no sense at all. We must ask 'moving relative to WHAT?'. The usual student's answer is: "relative to the magnetic field".

- Teacher: "How can you tell a 'moving' from a 'stationary' field?" ... That's IMO a possible entry point into relativity. From magnetism!

 

[Hurkyl]

The magnetical field is a relativistic effect, it's not a part of the classical physics. What's wrong with poles?

[?]

Magnetostatics predates relativity by quite a bit...

 

[QuantumNet]

Originally posted by arcnets
Well for one thing, I've never seen an exact definition of 'magnetic pole'. Maybe it's the point of a magnetic body's surface where the magnetism is strongest, or where the force is at right angles with the surface... but then you got to define 'body' and 'surface' which may lead to trouble.

Yes it's a relativistic effect. Please let me babble some more about teaching physics: My personal concept is sort of 'the other way round': Introducing relativity via magnetism!

Don't make it harder than it is. Both the charges are relativistic,
as mass.

 

[zare]

there is no "magnetic poles" in real world. it's just there for reference point. same with electromagnetic field lines. they don't exist, but they show us the density and direction, and uniformity of that field in mathematical models or simulations.

 

[turin]

Originally posted by zare
there is no "magnetic poles" in real world. it's just there for reference point. same with electromagnetic field lines. they don't exist, but they show us the density and direction, and uniformity of that field in mathematical models or simulations.

Are you saying that the field themselves don't exist!? It is pretty obvious (painfully so) that the lines are just a mathematical construct, so I'm going to assume that you meant the fields themselves (otherwise, I don't understand why you bothered to make such a vacuous statement). If the fields don't really exist, then how does electromagnetic energy propogate?

 

[arcnets]

Originally posted by QuantumNet
Don't make it harder than it is. Both the charges are relativistic,
as mass.

Yes, of course you are right. But see, In a course like this I'm trying to introduce what 'relativistic' means. A magnetic field is relativistic in the following sense:
If observer A sees just a magnetic field, then observer B (moving relative to A) sees an extra electric field¹. This leads to the idea that forces are relativistic. Students thought they weren't. Well if forces are relativistic, then other observables might be, too. Like space and time, themselves. That's why I think it's an entry point (at school...).

¹Yes I know the magnetic field is also different - but of higher order in v/c - no need to analyze this here.

 

[zoobyshoe]

Fairfield,

It might be of some comfort to you to find out the encyclopedia I have specifically addresses this issue as a problem:

"Simple rules were needed to deal with a simple action-at-distance experience, and soon the rule emerged that the lodestone has poles that pointed north and south. This was followed by the rule that `Like poles repell, unlike poles attract.'

The ready availability of permanent magnets focuses attention away from the closed-circuit nature of magnetism, which is far more useful in engineering than is the pole concept. Arguments against the circuital concept are that, unlike electric circuits, magnetis circuits cannot be insulated because the corresponding magnetic conductivity of air or empty spaces is finite and only about a thousand times smaller than that of the best magnetically conducting steel. Faraday likened the design of magnetic circuits to the design of electric circuits using bare copper wire in a bath of salt water (a good conductor of electricity). Although the electric circuits of most electrodynamic machines are complex and consist of coils with many turns of thin wire, their magnetic circuits are simple, short, fat and consist of a single turn.
The disadvantages of the pole concept are that it presupposes isolated poles in space; these have not been found, despite searches (isolated electric charges, however, do exist); and that troubles arise when trying to predict reactions between permanent magnets and other, initially unmagnetised, pieces of ferromagnetic material. For this purpose the law of induced magnetism has been invented, implying that the proximity of a primary magnet pole to a piece of soft iron induces an opposite pole in the latter nearest to the magnet and a similar pole at the point most remote from the magnet. There are a number of experiments which are very hard to explain on the basis of poles alone, while the circuit concept sees no difficulty in such arrangements: the pieces will always take up a position of minimum reluctance (that is, minimum impediment to the flow of flux) within the prevailing mechanical constraints. The circuit theory sees a magnet's pole merely as a change in reluctance between different parts of a magnetic circuit."

-The New Illustrated Science and Invention Encyclopedia
H.S. Stuttman Inc. Publishers
Westport CT 06889 1987 edition
Vol. Eleven, Pages 1510-1511, In the article: Magnetism
(Many libraries have this encyclopedia.)

So, you are by no means alone in seriously questioning the ramifications of this convention. But as this learned gentleman pointed out:

Originally posted by chroot
The two ends of a bar magnet obviously do different things to a compass needle, so they deserve two different names. The choice of north and south is arbitrary -- call them "slargbast" and "meedle" if you like.- Warren

We still very much need some handy vocabulary to distinguish the north pole from the south pole because they behave differently with respect to each other.

-Zooby

 

[Fairfield]

Originally posted by zoobyshoe
Fairfield,

It might be of some comfort to you to find out the encyclopedia I have specifically addresses this issue as a problem:

-Zooby

It still doesn't summarily dismiss magnetism as a purely secondary phenomenon, like the sound of a whistle, which is an identifiable phenonen, but which is only a rearrangement of a force which is already there (motion of air).

In the case of "magnetism", a force which is always present around a straight current carrying wire becomes more manipulatable when the wire is given a two dimensional shape in space. When the wire is formed into a loop, the tubular shaped force surrounding it has to take on the shape of a doughnut, but a doughnut with no poles of its own. Depending on the relative current directions in two such force doughnuts, when near each other, they may either attract each other or repel each other, just like straight wires. But now we may reverse the relative current of one or the other wires just by manipulating one of the loops rather than changing its electrical connection at a battery. But there is no need to give this alternative arranged attractive or repulsive force a new name, (edit=) magnetism, just because it is now in the shape of a more manipulatable doughnut.

Also see my post at the bottom of page 4 of the thread Classic Magnetism.

Fairfield

 

[zoobyshoe]

Originally posted by Fairfield But there is no need to give this attractive or repulsive force a new name just because it is now in the shape of a doughnut.

I'm not sure which "new name" you're referring to in this sentence. The title of the thread calls the concept of "poles" into question. But do you mean "magnetism" in the above sentence? If it is the latter, then the problem arose because knowledge of the doughnut shape preceeded knowledge of the simpler shape by many centuries. All the "doughnut case" vocabulary was already in place.

In general I gree with what this Gentleman said:

Originally posted by Albrecht
Don't forget that the magnetic lines of force are nothing different than a picture we build for ourselves, to handle a magnetic field in practice. There is no correspondence in theory because magnetism is not a force by itself but only a relativistic side effect of the electric field.

So, if we want to understand a magnetic situation really, we have to look to the electric situation and then take into account the limited velocity c by which field changes are propagated, and the relativistic contraction of a moving chain of electric charges.

-Zooby

 

[Fairfield]

Zooby:

OK, I'll buy all that in your post above; except the second part of the quote from Albrecht brings up, again, the situation of a changing electric field, which doesn't happen much outside of an electromagnetic radiation (wave), and I think that keeps confusing you.

As for the phrase, "magnetic lines of force", I could rest easy with that phrase if only it were more commonly carefully defined. Otherwise I, and probably most people, am/are first inclined to think of it as an independent force, or an alleged independent force, such as it originally appeared to be in lodestone, as you mentioned in your post above.

With that thought in mind I would like to offer my idea of a more careful, but simplified, definition of magnetic lines of force. Please keep in mind that nothing needs to be changing to display this kind of magnetism.

(First draft)
Magnetic lines of force around a coil (I don't believe they really exist around a straight wire except as a name place holder in diagrams.) should be defined as the rearranged lines of attractive and repulsive forces that exist between any relatively parallel current components that exist, and in this case between the parallel components between adjacent DC powered coils in any of their relative orientations.

As for that Faraday experiment, I am suspicious that the current in the mercury is reacting with the magnet's field, causing the mercury to circle. Also the moving wire has a tilt which may have enough transverse component in it to react with the magnet's field, like the field winding of a motor with a rotating field.

 

[kartiksg]

Hi guys,

I agree with arcnets. One must allow for the proper understanding of the principles of relativity in high school. One should not introduce it individually in itself, but must mould it with the concepts of electricity and Magnetism. In my post on Classical Electromagnetism, I was under the delusion that forces do not relatively transfrom. Thanks to ambitwistor, now it is not so. If u see my confusion and argument, they run on similar lines as that of fairfields. Do let the students know about poles. But why do u emphasise on poles and then say that poles don't exist? What is the pole?... My whole science stream class mates will respond ( that's about 200 of them ) that it would be the pole of a magnet.. or one end of a magnet. And yet, in places, we are taught that the pole is slightly behind the actual end of a magnet. We are taught about current loops creating poles and then told that no poles exist. And when it comes down to writing ur term exam.. nobody gives a damn bout if they understood or not... just put in values for B mu, I, l and pi get some stupid value.. underline it.. get 5 marks.. go to the next question. And if u do ask doubts, the general attitude in the class will be 'Shut up, sit down, and read the book'. Students must be given a first hand experience of what they are learning. Are we allowed to experiment on oersted's experiment? How many of us students have tried to see if 2 wires with parallel currents really attract? How many have seen an LCR circuit? How many have seen a van de graff generator at work? How many are allowed to use relays to really see if those half and full adders that we learn work? The list goes on and on...

These days, one must know a subject fully and thoroughly before teaching it. If not so, misconception and false ideas will prevail amongst students. No body will want to think if they are not expected to or are asked to.

Bottom line... offer peanuts and u get monkeys

Kartik

 

[zare]

turin, i said electromagnetic field lines, not fields. you know, like design schematic of solenoid coil. central lines go troughout the coil from inside out, while top and bottom lines curve themselves around wire loops and make circles and eddies. the drawn density of those lines predicts em. field density. what i wanted to point out is that those lines do not exist on real model, they are only references in mathematical model for visualization of em. field.

 

[zoobyshoe]

Fairfield,

I think that by limiting your definition to current carrying coils you are barking up the wrong tree. I really think it has to be defined in terms of charge.

Also, I'm not confused about the static vs electromagnetic wave. The point of contention is much more about what constitutes the difference between an electric and a magnetic field. I had assumed it was the kinks in all cases. I wasn't married to that idea, it just seemed to be what the sources were saying. Apparently when it comes to the case of a current carrying wire they aren't saying anything, simply that is it so. I don't find that very insightful.

 

[Fairfield]

Originally posted by zoobyshoe
Fairfield,

"I think that by limiting your definition to current carrying coils you are barking up the wrong tree. I really think it has to be defined in terms of charge."

OK. Moving charges. But these charges have been somewhat usurped, maybe completley, by the positive charge that is moving them. So maybe moving charges is not the whole story.

Originally posted by zoobyshoe

"The point of contention is much more about what constitutes the difference between an electric and a magnetic field."

In my opinion, regarding coils and magnets, its only the effect of a different shape of the "electric" field (more focused),the term "electric field" being in, this case, a stand-in for the interactive forces between parallel wired currents (attraction or repulsion). In straight wired currents I believe people simply became hypnotized by the responses of magnetic compass needles (which have rearranged "electric" fields themselves).