- Thu Jun 24, 2004 11:51 am
I found this AVC topic by entering that subject in Google. I was surprised to find a forum discussion going on about the matter. But it looks like there isn't any current commercial solution to my particular complaint. Strangely, all the background music I've heard this weak has been nice and soft.
However, since you are apparently pretty deep into electronics I wonder if I might lay on you a rather pedantic discussion regarding the seeming poor semantics involved in the standard definition of magnetism. I have only a casual layman's curiosity about physics, but in considering the standard description of magnetism, it seems to me to be incomplete. Incomplete because of a semantic hang up. I have put this complaint on a couple of physics forums but I have gotten little response, all negative. But the respondents don't come out and say that this or that statement is dead wrong. So if basic physics isn't a too old subject for you, I wonder if you might give my complaint a look?
In studying magnetism, and magnetic lines of force, it appears to me that a problem arises from misconstruing what a magnetic compass needle is really indicating when it is placed near a straight vertical direct current. The name magnetism was originally applied to certain objects (including, later, magnetic compasses needles) which would display north-south polarized MUTUAL attraction, or repulsion, with a measurable FORCE. Therefore, using sound semantics, you can't really have real magnetic lines of force (or magnetic lines of "field") without two such objects directly on any alleged magnetic lines of force. Therefore, to apply this name to something which supposedly encircles a current carrying wire, but doesn't have two objects to refer this alleged force (or field) to, redefines the meaning of the phrase "magnetic lines of force" in midstream. It appears to me that this redefinition follows from falsely assuming that any active magnetic compass needle indication always refers to magnetic lines of force (or field). But I think I show below that this is not the case. Therefore, this assumption constitutes a mere declaration rather than a scientific, or logical, finding.
To explain this, apparently inadvertent, switch in the meaning of the phrase, "magnetic lines of force", when it is applied to the area around 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 types of objects which, unknown to everybody at the time, contain looped currents for there particular force manifestation; which, therefore, have, spatially speaking, no less than two opposing parallel currents in them (opposite sides of the loop or coil, or the electrically equivalent situation in magnets). Since a straight wired current in no way has a either a loop, or two opposing currents, it does not qualify, according to the original definition, as a magnetic object. It, therefore, cannot, according to good semantics, generate magnetism, or magnetic lines of force (or field).
The situation of a magnetic compass needle near a straight current is a different kind of relationship (easily explained below) than between a magnetic compass needle and a magnet. Therefore, a magnetic compass needle near a straight current falsely projects, in one's imagination, something to which the original meaning of the phrase, "magnetic lines of force", does not apply.
It would be better to call these compass indicated "north-south" lines around a straight current, "Oersted's, right angled offset, current direction indicators", because they are simply derived from the physioelectric response of a loop current (or a magnetic compass needle's equivalent currents) near a straight current, depending on the straight current's and the loop current's comparative directions. In my opinion, this kind of physioelectric effect between currents, whether there is a pivotal loop current device involved or not, should properly be called Ampereism, not magnetism (see below).
To have a name kicking around in science which has two different meanings is not a helpful thing in my opinion. If the incorrect name, "magnetic lines of force", for this particular situation (magnetic 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 supposed indicated lines there be changed to "Oersted's lines of no force", or perhaps to "pseudo magnetic lines"
Further, by careful definition, you also can't have "lines of magnetic force" around the individual wires of a direct current carrying coil, because you only get genuine magnetism off the faces of a loop, or off the ends of a tubular coil, or off the ends of a magnet, (or magnetic compass needle) as a MUTUAL VECTOR RESULTANT FORCE from at least two pairs of opposing parallel currents (at least 4 parallel currents altogether), at least one pair in each magnetic entity, when they are brought near to each other. This mutual vector resultant force varies with different orientations between any two magnetic entities. However, around the individual internal wires of a coil, you only have pseudo magnetic lines. These lines of no force, naturally, cannot be added up to create a net magnetic force. However, there are radial lines of Ampereic attractive force around each wire which must be added up. But proper semantics demands that this radial force around each wire of a current carrying loop, or coil, should NOT be called magnetic force.
Since genuine magnetism, according to the original definition, requires at least two parallel opposing currents in each magnetic entity, it seems clear to me 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 seems only proper to call this more primary force system, Ampereism; and the forces operating there, Ampere's radial lines of physical force.
From the above considerations, it appears 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 provides only a confusing view of Ampereism.
What both loop currents and 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 type field's electrical and physical effects. But it is not helpful, in my opinion, to drag around ambiguous meaning names. A straight wire current's inductive field is just that. It is not a loop current's inductive field, so it is not a magnetic inductive field. On the other hand, a magnetic inductive field is, spatially speaking, a combination of at least two sub inductive fields. If a common name is going to be used for both types of inductive fields, and the lines for their flux densities, it seems to me that it should be something like Faradayic flux density" instead of "magnetic flux density".
I hope this verbal puzzle interests you for a while.