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Name: Zak 
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Question:
I was wondering if it is possible to make a spherical magnet that its polarity is not "through" the magnet? Essentially, I am pondering if it is possible to make a tetrahedrak\l magnet with the surface of the magnet all being one polarity. So if I were to say have it be a N polarity magnet then anywhere on the magnet that I put a S polarity it would attract, all 360 degrees of it.



Replies:
Sorry, Zak, not possible.
What you seem to be describing would be considered either
A) a magnetic monopole, which nothing has ever been found to create, or
B) dipole layers around a sphere, which sends no field to the outside.

So far, just like electromagnet coils, all magnets have N and S on the outside. "But my sphere has N buried in the center", you say? Well, then, if it can be made, all the magnetic lines of force will be going from the N to the S and stopping there, and so none go outside the sphere, so there will be no magnetic forces or attractions outside, even though there are forces inside.

Actually, with no magnetic static charges (monopoles) existing, all magnetic field lines are closed loops, i.e., distorted circles. The typical field lines in a bar magnet go from S to N within the magnet (being pushed by all the magnetized iron they pass through), then sail smoothly through the "N" volume and keep on going outside the magnet, arcing around through the air from N back to S. If there was a tiny flea with magnetic monopole charge, (maybe "Warehouse13" has one) the looped lines of an electromagnet coil would push it through the center and back around the outside, over and over forever. Same with a bar magnet, except then there is some iron blocking its motion.

Given these loops, it is hard to see what your sphere-magnet means, other than complete frustration of the magnetic field. Think about it, lines go from inside (S) to outside (N), and then where? If they go out, they can never turn around and come back to the S, because your sphere is perfectly the same in all directions, no parts stronger or weaker. If the lines turn in the N layer and fall back to the S layer inside, then they cancel out the first lines coming out.

If you made a bunch of wedge-shaped bar-magnets (no problem) and jammed them together to make a sphere, their new position would stop all their magnetic flux, inside and out, and push back unusually hard to de-magnetize them.

There is a distinction between "magnetizing force" and "magnetic flux". Force in Oersteds, flux in Gauss, to use old units. Flux is the familiar magnetic field lines which push things around. Force is an unseen "something" that pushes on space to make a flux in it's direction. The resulting flux is then some aspect of space bending from that force in a springy fashion. In physics terminology, empty space has some permeability to magnetism. But we do not think about magnetic force much. It does not make close analogies to other things in our experience too easily. If you can someday build yourself a good mental picture of it, it will clarify questions like this greatly. The iron in a permanent magnet exerts some of this "magnetizing force" within its bulk, and a current through a wire exerts some around the outside of the wire. Coiling up such a wire makes many small magnetic forces add together running down the middle, so there is a stronger magnetizing force inside a solenoid.

Mechanical forces caused by magnets typically result when a loop of flux is stuck going through two objects and the empty space between them. Said loop wants to shrink. If the length of the flux-path through empty space decreases, the energy of that flux loop is lower, because less space is being "bent". Force x distance = work = Energy, and usually the converse is true: d(Energy) / d(distance) => Force. ("d" for "delta", means the difference after some change.) Anyway, all this means that both N and S lines must emerge from a magnet, to put a force on any other object. And both N and S lines must reach the object, too. Magnet force is more like a two-handed crab (with stretchy arms), than like a spear with a string.

Jim Swenson


A magnetic monopole has not been found.

Here is a good summary of the state of the search for magnetic monopoles in Wikipedia.

http://en.wikipedia.org/wiki/Magnetic_monopole

Sincere regards,

Mike Stewart


I think not but that is only intuition, which is about that value. I have purchased a number of magnetics from "K & J Magnetics" and have found them very receptive to questions such as the one below. I don't have an answer, but it may be out there. Possibly re-redirect the question to "K&J" for some direction.

Vince Calder



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