Stephen A. Lawrence wrote: > > > Paul wrote: >> Stephen A. Lawrence wrote: >> [snip] >> > > They attract until they are perfectly aligned NS >> NS. >> > >> > When they're aligned >> > >> > N >> > | >> > | >> > | >> > | >> > S >> > N >> > | >> > | >> > | >> > | >> > S >> > >> > they can flip (rotate) so that they're aligned >> > >> > NS >> > || >> > || >> > || >> > || >> > SN >> >> >> Sure if you ***add*** energy Stephen. That takes >> energy. I have written far too many simulations to know. I have seen >> physical grids of >> permanent magnets on swivels and you are completely wrong on this. >> Magnet dipole moments >> prefer NS....NS. > > Really?? Sigh.... > > That's what I get for relying on intuition.
It seems intuition is probably the most important tool in theoretical research. Einstein spent his entire life trying to find an intuitive theory. :-) A good process seems to be intuition followed by theory followed by experimentation. > I certainly had not done > any calculations to show which way they should end up -- the potential > energy and force calculations by themselves don't say. And we don't > have any sufficiently whizzy bar magnets here to let me test it > macroscopically. (But see below in this note -- uh, oh, it sure looks > like you're right...) There you go again with your cigarette dipoles. ;-) Who knows, perhaps the cigarette is the true shape of the electron, but I doubt it. QM claims the electron has no physic extend beyond the Poynting vector. > > BTW, your drawings of >> dipoles are way out of proportion. You are drawing cigarettes. An >> electron is not in the >> shape of a cigarette, lol. > > Well, yeah, they're kind of stubby, aren't they. Not quite like a bar > magnet, not at all... > > >> > It increases versus a single magnet, that's true. But compared with >> > two distant magnets? I'm not so sure; we need to >> ask: >> >> No, the net magnetic field increases from two nearby >> fully aligned magnets as compared to if they were far apart. >> >> >> > Does the field increase or decrease as they're >> drawn apart along a >> > line? >> >> More of the fields overlap as they approach each other >> in fully alignment. > > So it appears. And certainly the result is far larger field energy than > the half-aligned case, however it may compare with the case where > they're far apart. Here's perhaps a simple method of viewing the issue. Consider two loops of current carrying wire in free space. Consider the fact the dipoles will slowly dissipate their energy by means of radiation resistance; i.e., dipole KE gained is lost over time. Ultimately the wires will end up side by side, like two donuts hugging each other. Remember currents flowing in the same direction attract. All the current carrying wire cares about is getting as close to the other wire as possible. The closest orientation is face to face, thus nearly forming one wire loop. >> > [ snip ] >> > >> > > Two aligned electromagnets do not repel. They >> > > *attract*. >> > >> > Arrgh. We're both right. If they're end-to-end >> they attract when >> > they're aligned. If they're side by side they >> attract when they're >> > misaligned. >> >> Correct, but what you seem to miss is the front >> magnetic density is twice as compared to the sides, > > Ummm hmmmm so it is, the field strength ratio at the end versus the side > is something like 2:1, and, if the dipole is allowed to align with the > field, the net force it feels is always in the direction of increasing > field strength. For a point charge it is. Of course if for example the dipole is 1 cm in diameter and you're testing the field right up against the wire millimeters away then it doesn't make sense you'll get 2:1 ratio. Did you try to field dipole moment calculator? http://www.netdenizen.com/emagnet/offaxis/iloopcalculator.htm Regards, Paul Lowrance ____________________________________________________________________________________ Yahoo! Music Unlimited Access over 1 million songs. http://music.yahoo.com/unlimited
