Magnetism

[Magnetic]

*Disclaimer - This thread has nothing to do with my other posts regarding the Christian Forum.


I have a question about the characteristics and/or properties that cause two magnets to either attract, at opposite polls, or repell, at same polls. On an elementary level, it almost appears to be a 'magical' property. Two pieces of material, somehow having the ability to attract or repell another of it's kind, and the ability to attract metallic objects. I have some rare earth magnets. Fairly small in size, but increadibly strong, but by themselves, they just look like pieces of metal.

My question is, for those of you with physics backgrounds, what is this property that produces the magnetism in something like these rare earth magnets?

Thanks!

[General Zod]

This is basic google stuff. A brief explanation on Ferromagnetism

[Magnetic]

That's a good link. Thanks.

But there is still a question of how that process came about, the aligning of electrons and how that produces a repelling or attraction. It spoke of both the atomic and quantum levels, but I'm afraid that may be beyond my present state of knowledge. Anyway, the site did a good job of explaining the process, but what about the principle behind the process, because just knowing about the aligning of electrons doesn't explain the "why it happens", unless I missed it in that link, which is very possible.

[Xenophobe3691]

That's a good link. Thanks.

But there is still a question of how that process came about, the aligning of electrons and how that produces a repelling or attraction. It spoke of both the atomic and quantum levels, but I'm afraid that may be beyond my present state of knowledge. Anyway, the site did a good job of explaining the process, but what about the principle behind the process, because just knowing about the aligning of electrons doesn't explain the "why it happens", unless I missed it in that link, which is very possible.

Why what? Why does "magnetism" happen? In the general sense of "Why does Magnetism exist?" I'm confused...

[Magnetic]

That's a good link. Thanks.

But there is still a question of how that process came about, the aligning of electrons and how that produces a repelling or attraction. It spoke of both the atomic and quantum levels, but I'm afraid that may be beyond my present state of knowledge. Anyway, the site did a good job of explaining the process, but what about the principle behind the process, because just knowing about the aligning of electrons doesn't explain the "why it happens", unless I missed it in that link, which is very possible.

Why what? Why does "magnetism" happen? In the general sense of "Why does Magnetism exist?" I'm confused...

Yes! All those things. Thanks!

[Darth Wong]

That's a good link. Thanks.

But there is still a question of how that process came about, the aligning of electrons and how that produces a repelling or attraction. It spoke of both the atomic and quantum levels, but I'm afraid that may be beyond my present state of knowledge. Anyway, the site did a good job of explaining the process, but what about the principle behind the process, because just knowing about the aligning of electrons doesn't explain the "why it happens", unless I missed it in that link, which is very possible.

Why what? Why does "magnetism" happen? In the general sense of "Why does Magnetism exist?" I'm confused...

Yes! All those things. Thanks!

Why assume there must be a reason? It simply exists, much as the universe does. It need not have a "reason". I often hear religious people ask questions like this, to which I usually respond by asking "why does God exist?" When they answer that he is simply eternal and we should not ask such questions, I simply replace "God" with "the universe" in whatever sentence they use and fire it back at them.

[Admiral Valdemar]

Why assume there must be a reason? It simply exists, much as the universe does. It need not have a "reason". I often hear religious people ask questions like this, to which I usually respond by asking "why does God exist?" When they answer that he is simply eternal and we should not ask such questions, I simply replace "God" with "the universe" in whatever sentence they use and fire it back at them.

That works fine most the time, but when you come across a guy who has read far too much philosophical sophistic bullshit text, you end up going on for pages (five or so last time I came across this type) trying to explain the point clearly enough. And after that, they may just try and use some physics to show the Big Bang was the start and the universe was never eternal or say the universe cannot be infinite because we'd never get up to this point in time if it were. I wish I made this up.

[Kuroneko]

One can only push explanation so far, but in the case of magnetism, it is possible to fall back on the movement of electric charge (of course, the next natural question would be 'why does electric charge exist?' or something to that effect, but that's beside the point). Picture a stationary charge located at the origin of the (x,y) coordinate plane. Draw a few of the electric field lines uniformly and symmetrically distibuted around it--these are very simple, going radially outward from the origin. Let's say, one line on the x-axis (y = 0), another on the y-axis (x = 0), two directly inbetween them (y = ±x), and four more directly inbetween those (y = ±x/4, y = ±3x/4). The symmetry of the lines drawn represents the fact that the force is equal in all directions. Add more as you feel necessary.

Now, suppose that the charge is moving in the positive x direction with some velocity v. According to the theory of special relativity, is measure of spatial distance will be contracted along this direction by some factor γ>1 (pick some value). That means a given point (x,y) is mapped onto the point (x/γ,y), so that, for example, any given electric field line y = mx is transformed into y = γmx. This increased density of electric force lines in the perpendicular direction of motion means that a test charge located in the perpendicular direction of the moving charge will experience more force. The magnetic field of the moving charge is then simply a way to formalize the difference between the transformed field and the stationary field without actually changing the electric field. One can view the magnetic field assimply an epiphemonon caused by insisting that the electric field is the same in both cases--in the end, that view has certain advantages, as doing the relativistic transformation on a complex collection of charges is simply not worth it, while adding up the magnetic field contributions of which is relatively easy. For mathematical details of this transformation, see, for example, J.D.Jackson, Classical Electrodynamics.

It is worth noting that the phenomenon of electromagnetic waves is also explainable in this way, although it is not mentioned in Jackson (I can't any references for it on my bookshelf; I'm recalling this explanation from deep and vague recesses of memory, but I think it was originally made by Sir J.J.Thomson, the discoverer of the electron). What is frequently found most puzzling about electromagnetic waves are that (1) they act in the transverse direction, rather than the direction of their motion, and (2) their field strength falls of inversely with distance, rather than the square of the distance. To see why, begin again with a stationary charge in the (x,y) coordinate plane, with some sample electric field lines. Give it an instantaneous impulse along the x direction to some velocity v<c, and wait some time t. Draw a circle of radius ct around the origin; since special relativity forbids the propagation of information faster than lightspeed, the universe outside this circle is not yet informed of the fact that the charge was accelerated. The charge itself is now at position x = vt, so draw an electric field of a moving charge (as described the previous thought experiment above) within the circle. At the edge of the circle, there is a problem: the field lines would have to turn sharply, go along the circumference, and rejoin the (untransformed) lines outside of the circle. This sharp turn is, in fact, the electromagnetic wave, and it is easy to see why it acts transversely--because the field line there is perpendicular to the direction in which it is traveling. Some on-paper experiments with many field lines and several different sample times t will show that the density indeed falls off inversely with radius.

Of course, the above explanations handwave away a lot of mathematics, I think this picture is in some ways more intuitive and understandable for beginners, as is your case.

[Magnetic]

Thanks, Kuroneko. For a 'beginning' look at magnetism, it was still deep enough.

I decided on the screen name "Magnetic", because I find it very fascinating. Before I had access to these Rare Earth Magnets, I only was acquainted with those other less powerful magnets, and although they were mildly interesting, when I began experimenting with the Rare Earth Magnets, I began to be very interested in how they work.

One thing I find interesting is that if a magnet gets broken in half, they will begin repelling at that point. Pretty interesting, though.


Oh, Darth Wong, I won't be saying anything to the sort that, "because we don't understand it, therefore God makes the magnet work".

[TheDarkOne]

For mathematical details of this transformation, see, for example, J.D.Jackson, Classical Electrodynamics.

Or Griffiths' Introduction to Electrodynamics, that book is great, easily one of my favorite text books to date.