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darkdev
2004-Apr-14, 01:15 AM
Is it possible to create a magnet, in a circular shape, such that there is no clear north or south pole?

For instance, if you take a bar magnet, and cut it in half, in the middle, you get two magnets both with N/S poles:
[N---S] becomes [N-S] [N-S]

If you bend this magnet into a circle first, and attach the N and S poles, and the cut it elsewhere and straighten it out, you end up with another bar magnet with definate N/S poles.

So... if you can create a poleless or continuous magnet (in the shape of a doughnut), would a compass needle centered over the magnet spin forever looking for a pole? Can we use this rotation as a fuel-less electromagnetic power supply?

hmmm.... doughnuts.....

milli360
2004-Apr-14, 01:25 AM
So... if you can create a poleless or continuous magnet (in the shape of a doughnut), would a compass needle centered over the magnet spin forever looking for a pole?
It doesn't look for a pole, it aligns itself with the field. With no N-S direction, there's no field. No spinning.

Can we use this rotation as a fuel-less electromagnetic power supply?

hmmm.... doughnuts.....
There's a reason they call it dough nut

Patrator
2004-Apr-14, 01:49 AM
darkdev wrote:

So... if you can create a poleless or continuous magnet (in the shape of a doughnut), would a compass needle centered over the magnet spin forever looking for a pole?

It's quite a while since I did any work on magnets but IIRC.

If you create a poleless magnet in the shape of a doughnut (incidentally it's called a Toroid), the magnetic flux follows a circular path mostly within the toroid. It's the path of least magnetic resistance i.e. highest permeability. As Milli360 has mentioned, the compass needle will simply align itself with the lines of flux or field if you prefer. If you placed a compass exactly in the centre of the toroid, where there is no net flux, the compass would point North (because the Earth's magnetic field is still present!). Anywhere over the toroid and it will point at a tangent to the edge of the toroid.

darkdev
2004-Apr-14, 02:01 AM
I actually swapped toroid for doughnut just to make the Simpsons reference.

Thanks for the answers. That makes a lot of sense.

Since I'm new, is there a forum already open discussing the true source of magnetism? The search engine here seems to suggest that magnets come up but are not a topic... maybe I missed it?


There's a reason they call it dough nut
"Nuts" is having a question and not seeking the answer, or assuming your instinctual response is correct.

Ricimer
2004-Apr-14, 02:54 AM
actually, a toroid, like a solenoid, has an isolated magnetic field. THe magnetic field does not extend outside of the coiled wire. So placing a magnet, even over the ring, shouldn't cause a deflection.

TriangleMan
2004-Apr-14, 11:07 AM
Since I'm new, is there a forum already open discussing the true source of magnetism? The search engine here seems to suggest that magnets come up but are not a topic... maybe I missed it?

Nope I don't recall any other recent threads on magnetism so this would be the right place for it. :)

darkdev
2004-Apr-14, 11:10 AM
What is the "source" of magnetism?

PhantomWolf
2004-Apr-14, 11:18 AM
It's caused by electron spin, though the details are quite intricate nd I can't be bothered looking them up. :)

darkdev
2004-Apr-14, 11:28 AM
That much I knew, I am wondering what the mechanism is I guess, like gravity is local spacial configuration (spacetime curvature), does magnetism as a distortion in spacetime? Can we express E,M,G as a 3d waveform? It seems to be for EM.

Patrator
2004-Apr-14, 11:53 AM
actually, a toroid, like a solenoid, has an isolated magnetic field. THe magnetic field does not extend outside of the coiled wire. So placing a magnet, even over the ring, shouldn't cause a deflection.

Whilst this statement is quite correct, it applies to an induced magnetic field via an electric current. I believe Darkdev was talking about a permanent magnet with field alignment in a circular direction around the toroid. In this case, the magnet, whilst giving the overall effect of no poles, consists of many N-S domains all aligned around the circumference. The bulk of the field will remain within the toroid, but will, to a degree, extend outside.