In studying magnetism, It is clear to me that a problem arises from misconstruing what a compass needle really is indicating when it is placed near a straight current. The name magnetism was originally applied to certain objects which could display MUTUAL attraction or repulsion with a measurable FORCE. You, therefore, can't have real magnetic lines of force without two such objects. Therefore, to apply this title to something which (supposedly) circles a current carrying wire, but doesn't have two objects to refer this force to, redefines the meaning of the phrase "magnetic lines of force" in midstream. This redefinition follows from falsely assuming that any active magnetic compass needle indication always refers to true magnetic lines of force. This is absolutely not true.

To explain this inadvertent switch in the meaning of the phrase, "magnetic lines of force", as it is applied to a straight wire current, we have to consider what the true definition of magnetism originally referred to, and therefore, should continue to refer to, unless formally redefined.. The term "magnetism" was originally applied to objects which, unknown to everyone at the time, contain looped currents for their particular force manifestation, which, therefore, have, spatially speaking, no less than two opposing parallel currents in them (opposite edges of the loop or coil). Since a straight wired current in no way has a either a loop, or two opposing currents, it does not qualify as being a magnetic object, and it, therefore, cannot generate any magnetic lines of force.

The situation of a compass near a straight current is a different kind of relationship (easily explained) than between two genuine magnetic objects (of which the compass needle can be one of them). The compass needle therefore, near a straight current, falsely projects, in one's imagination, something to which the original meaning of the phrase, "magnetic lines of force", absolutely does not apply as explained above.

To have a name (phrase) kicking around in science which has two different meanings is not a helpful thing. If the incorrect name, "magnetic lines of force", for this particular situation (compass indication near a straight current) has been incorporated into so many physics formulas that it can't be extricated, or if it is used in a monitoring/calculating reference system, then I suggest that, at least, the name of the indicated lines be changed to "Oersted's north-south lines" (OF NO FORCE), and the term "electromagnetic waves" be changed to "electro-Oersted 'waves' ". It would be even better, but a mouthful, to call these compass indicated "north-south" lines around a straight current, "Oersted's right angle current direction indicators", because they are simply derived from that by the physioelectric response of a (equivalent) loop current (of a compass) near a straight current, depending on the straight current's direction. This kind of physioelectric effect between current carrying wires should be called Ampereism instead of magnetism (see below).

Further, you also can't have those, "lines of magnetic force", (in magnetic field diagrams) around the individual wires of a current carrying coil because you ONLY get genuine magnetism off the end of a loop or a coil as a MUTUAL resultant force from the two sets of opposing parallel currents, one set in each magnetic entity, when they are brought near to each other. The mutual vector amount of this force varies with different orientations and distances between any two magnetic entities. Aside from that coil, (mostly) "end" effect, you don't have any other genuine magnetic lines of force present Only 'Oersted's lines of NO FORCE' "around" the single internal wires. These lines of no force, naturally cannot be added up to create a net force.

Since genuine magnetism requires at least two parallel opposing currents in each magnetic entity, it is clear that magnetism is a more complex arrangement of a more simple force system relating to the physical reactions between close parallel currents. Since it was Andre M. Ampere who first discovered this physical reaction between close parallel currents, it would seem proper to call this system, Ampereism, and the forces operating there, Ampere's lines of (radial mutual) force.

Finally, from the above considerations, it is clear to me that the overall problem of properly relating magnetism to electricity is that magnetism is a superstructure forces relation system built up of a lower order forces relation system, which latter system should properly be called Ampereism. Therefore magnetism, if not looked at closely, provides a confusing view of electro-Ampereism, and a confusing view of the relationship between magnetism and electricity.

Fairfield

At what level are you studying magnetism? "Magnetic lines of force" is a very misleading statement. What you are looking for, I believe, is magnetic flux density. Also, the "flow" of electricity is the flow of electrons, which causes a magnetic field at right angles to the electric field.

BTW, N/A means Not Applicable, and I hope that birthday is applicable to you!;)

One of the main reasons for defining a field is to be able to speak of it as an object in itself. The magnetic field itself is an object (sort of), that would theoreticall induce a force on a magnetic monopole. Since magnetic monopoles have not yet been observed, we have a law (one of maxwell's) that says this is the case. And then it becomes very tempting (and understandably so) to talk about magnetic field lines being rather artificial. There are, IMO, at least two problems with this view.

1) You are arguing with thousands of years of historical support in favor of calling the phenomenon "magnetism" and referring to the effect as a force.

2) The dual of the Faraday tensor suggests that there may be a magnetic monopole in terms of the symmetry of the field equations, and thus, there would be a direct magnetic force due to the magnetic field on objects that do not exhibit any inately electrostatic properties.

Originally posted by geodesic
"Also, the "flow" of electricity is the flow of electrons, which causes a magnetic field at right angles to the electric field."


I am not denying that there is a field around a current carrying wire which can induce a current in an adjacent wire with change or motion. But it is improper semantics to call it a magnetic field or force. It requires another name.

Obviously, a moving wire in a magnetic field will produce a current.
But so will moving a wire in a field which doesn't meet the definition of a magnetic field i.e. field around a lone current carrying wire. Just because the same results happen in the two different types of fields doesn't necessarily mean they are exactly the same types of sources.

Fairfield

Originally posted by Fairfield
Obviously, a moving wire in a magnetic field will produce a current.
But so will moving a wire in a field which doesn't meet the definition of a magnetic field i.e. field around a lone current carrying wire.

But a lone current carying wire PRODUCES a magnetic field!

Originally posted by John Connellan
"But a lone current carying wire PRODUCES a magnetic field"

A magnetic field is a magnetic field (requiring a magnet, or its equivalent). and a current carrying wire's field is a wire's field with only one wire. Obviously, by visual inspection, the two are not the same even though they produce a similar result. If you called the field of a magnet a multiwire field, you would be closer to the truth.

Fairfield

Originally posted by Fairfield
A magnetic field is a magnetic field (requiring a magnet).Who told you that? Does an electric field require an "electr?" Actually, let's start from the basics. What is your definition of a "magnet?"




Originally posted by Fairfield
and a wire field is a wire field with only one wire.A "wire field?" What is a wire field? I can picture a vast field of upright wires swaying in the wind.




Originally posted by Fairfield
Obviously, by visual inspection, the two are not the same even though they produce a similar result. If you called the field of a magnet a multiwire field, you would be closer to the truth.In support of my disagreement to this assertion, you do not need a wire to have a magnetic field.

Furthermore, I don't think the emphasis should be on the source any more preferentially than on the property of interaction.

So, in your opinion, it is OK for the wire field to interact with a magnet, but it is NOT OK for a magnetic field to originate from a wire?

Originally posted by errandir

"So, in your opinion, it is OK for the wire field to interact with a magnet, but it is NOT OK for a magnetic field to originate from a wire?"

Exactly so. The only logical excuse for a magnetic field to be called a magnetic field is because it is caused by a magnet or its equivalent.

Fairfield

Originally posted by errandir
A "wire field?" What is a wire field? I can picture a vast field of upright wires swaying in the wind.

U had me in stitches with this one !!!:D

Originally posted by Fairfield
Exactly so. The only logical excuse for a magnetic field to be called a magnetic field is because it is caused by a magnet or its equivalent.

Fairfield

No. That is not a logical excuse. It is called a magnetic field because it can be produced by a magnet. The important word here is CAN. I had an argument recently with someone like this. He claimed that a killer flu will kill people - thats why it is so-called. he was wrong. It is called a killer flu coz it CAN kill people. Not everyone is goin to die from it.

Other ways of creating the field (which was once thought to emanate SOLELY from magnets) is using a current carrying wire.

The force that causes the 'magnetic' behavior of a permanent magnet is the same force that causes the 'magnetic' behavior in an electromagnet. They are the same force: the electromagnetic force.

Originally posted by Fairfield
Exactly so. The only logical excuse for a magnetic field to be called a magnetic field is because it is caused by a magnet or its equivalent.Should I conclude from this logic that, if I observe an identical force on a magent that comes from another magnet as opposed to a wire, that the magnet is interacting with a completely different kind of field, just because there's no wire, even though, in all other respects, the effect is indistinquishable?

Originally posted by errandir
"Should I conclude from this logic that, if I observe an identical force on a magent that comes from another magnet as opposed to a wire, that the magnet is interacting with a completely different kind of field, just because there's no wire, even though, in all other respects, the effect is indistinquishable?"

It appears to me that you are comparing the attraction between two current carrying wires to the attraction between two magnets, or to two same direction current carrying coils. If this is correct then I have to say that regarding different kinds of fields in the two different cases, they are different only in their shapes. But in the case of the magnetic field, its focused shape ("beam" of attraction or repulsion) has warranted it acquiring a particular name. But if you employ a given name for a given shape, you have to stick with it, or formally broaden its definition. Otherwise, confusion results.

Fairfield

Originally posted by Fairfield
... they are different only in their shapes.Can you define the "shape" of a field?




Originally posted by Fairfield
... in the case of the magnetic field, its focused shape ("beam" of attraction or repulsion) has warranted it acquiring a particular name.What has acquired a particular name? The shape? What is a "beam" of attraction? What is a "focused shape?"

Originally posted by errandir
Who told you that? Does an electric field require an "electr?" Actually, let's start from the basics. What is your definition of a "magnet?"

If "electr" means electron. Yes, of course it does. My definition of a magnet is in paragraph 2 of this thread starter.

Fairfield

Originally posted by errandir
Can you define the "shape" of a field? What has acquired a particular name? The shape? What is a "beam" of attraction? What is a "focused shape?"

Refer to standard diagrams of magnetic fields.

Fairfield

One usually says that a circular current in a loop of wire has a magnetic field. But one can also say that a magnet, or it equivalent, has a circular loop current's field. Which statement is correct? Obviously, both statements are correct, but they are also both tautologies, which means the statements don't declare anything new except the naming of synonyms. That is a poor use of language, and shouldn't be allowed.

But let's skip the tautology complaint, and, just for the sake of argument, set aside the favored statement that a loop current has a magnetic field, and instead say that a loop current has a loop current's field. Then how does one sensibly say that a current in a straight wire has a loop current's field surrounding it? You can't do this without drastically stretching the definition of a loop current. This is abominable semantics. Why should physics students be subjected to such abominable semantics?

There is a common something there, but it isn't being properly verbalized.

Fairfield

Originally posted by Fairfield
One usually says that a circular current in a loop of wire has a magnetic field.

You are the only one that says that. What is said is that electric current (electric current is the motion of electric charges)generates magnetic field. The cureent needs not to be in a circular loop. Bio-Savar law says exactly how this field is generated. Each electric current configuration gives a different magnetic field.

Originally posted by Fairfield

But one can also say that a magnet, or it equivalent, has a circular loop current's field.

No, a magnet (I understand that you are talking of a permanent magnet)has a magnetic field generated by the charges that move in it and given by Bio-Savar law.

Originally posted by Fairfield

Which statement is correct? Obviously, both statements are correct, but they are also both tautologies, which means the statements don't declare anything new except the naming of synonyms. That is a poor use of language, and shouldn't be allowed.

Both statements are incorrect. There is one phenomenon which is that moving charges generate magnetic fields.
A special case of moving charges is moving charges that go in a closed loop. But this is a special case. What is not allowed to be said is that each moving charges are moving in a closed loop. This what you say.

Originally posted by Fairfield

But let's skip the tautology complaint, and, just for the sake of argument, set aside the favored statement that a loop current has a magnetic field, and instead say that a loop current has a loop current's field.

How can you ask to skip the tautolgy complaint, and in the next sentence say that the field generated by a current loop is afield generated by a current loop?

Originally posted by Fairfield

Then how does one sensibly say that a current in a straight wire has a loop current's field surrounding it?

You are the only one that says that. The magnetic field generated by a straight wire current is different from the magnetic field generated by a closed loop current.

Originally posted by Fairfield

You can't do this without drastically stretching the definition of a loop current.

What law says that the basic entity is a loop current?
Where do you use the loop current to calculate the magnetic field.
Why do you want to stretch the definition of a loop current in order to fulfill your semantics which are based on misunderstanding of what generates a magnetic field.

Originally posted by Fairfield

This is abominable semantics. Why should physics students be subjected to such abominable semantics?


I agree with you that it is abominable semantic to use misunderstood physics to prove misunderstood statements.
Physics students are not taught of what you said. Instead they are taught that moving charges generate magnetic fields, and this magnetic field is given by Bio-Savar law. What is wrong with that?

Originally posted by Fairfield

There is a common something there, but it isn't being properly verbalized.


I would rather say that it is not understood by you.

What both the loop currents and the straight currents have in common is they both have inductive fields which the working physicist and electrical engineer need to keep track of in order to get a mathematical hold on either field's electrical and physical effects. But it is not helpful to drag around confusing names. A straight wire current's inductive field (Ampereic field) is just that. It is not a loop current's inductive field, so it is not a magnetic inductive field. A magnetic inductive field is a resultant of at least two ampereic fields (spatially speaking). If a common name is going to be used for both types of inductive fields, and the lines for their (flux) densities, it should obviously be Ampereic flux density instead of magnetic flux density.

Fairfield

That's why, in 1967 electromagnetism and the weak force were postulated as being one force wearing different masks and unified into the electroweak force, the actual carriers for this electroweak force were found in 1983 by CERN.

Originally posted by Fairfield
If "electr" means electron. Yes, of course it does.Have you ever heard of a quark? Have you every heard of an electromagnetic wave?




Originally posted by Fairfield
My definition of a magnet is in paragraph 2 of this thread starter.I didn't see the word "magnet," per se. If anything, I found a rather indirect definition that seems to suggest:

magnet == an object in which there is a current loop

I totally disagree with this, but it's not my thread.