Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Atomic-S on 19/07/2016 07:07:47
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Consider a ring (toroid) composed of magnetizable material, that is converted into a permanent magnet having the lines of flux running circularly within the material about the toroid's axis. The lines of flux are everywhere at right angles to the axis, circulating around it within the toroid. Because they never enter or exit the toroid's surface, the toroid has no magnetic poles and no external field.
Now imagine mounting this toroid on a nonmagnetic axle that passes through the center but is at right angles to the axis, so that the axle also meets the toroid itself at opposite places. We shall assume that the axle is affixed to the toroid as by epoxy, but does not actually penetrate it, so that it has no effect on the toroid's internal magnetic field. For mechanical reasons, it also extends beyond the toroid on each side so the thing can be mounted in bearings with a drive mechanism. Now imagine the toroid spinning upon this axle.
Question: What effect if any will be experienced by electrical conductors brought into the near vicinity of the spinning toroid?
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If there is no external field no current can be generated
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There is no external field when it is stationary. But is that still true when it is moving?
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Consider a ring (toroid) composed of magnetizable material, that is converted into a permanent magnet having the lines of flux running circularly within the material about the toroid's axis. The lines of flux are everywhere at right angles to the axis, circulating around it within the toroid. Because they never enter or exit the toroid's surface, the toroid has no magnetic poles and no external field.
Now imagine mounting this toroid on a nonmagnetic axle that passes through the center but is at right angles to the axis, so that the axle also meets the toroid itself at opposite places. We shall assume that the axle is affixed to the toroid as by epoxy, but does not actually penetrate it, so that it has no effect on the toroid's internal magnetic field. For mechanical reasons, it also extends beyond the toroid on each side so the thing can be mounted in bearings with a drive mechanism. Now imagine the toroid spinning upon this axle.
Question: What effect if any will be experienced by electrical conductors brought into the near vicinity of the spinning toroid?
For a magnetizable material I don't think you can say there is no external magnetic field outside the stationary toroid. Maybe you can make it negligible in some way, e.g. covering the toroid's surface with mu-metal?
https://en.wikipedia.org/wiki/Mu-metal
If it worked, would this be the same for your experiment or you actually don't want any other kind of device/material added?
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I think we can say that there is no external field associated with the stationary toroid because of symmetry. That is, if such a field existed, it could not be symmetric with respect to the axis because that would require its value to be zero. However, the toroid is magnetized in an internally symmetric manner. Therefore its field must be entirely internal.
Based on that, my first thought is that the application of an external metal would make no difference. However, if the motion creates some kind of a field that was not there previously, then the external material may matter, specifically if it is electrically conductive. I would insist therefore that the material not be electrically conductive if the experiment were intended to actuate any other conductors in the region.