Fun with perpetuum mobile

[gumpzilla]

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I can't help thinking it'd be easier to find circumstances where you could take advantage of the fixed field than to harness the random fluctuations... but then, I am not a physicist.

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Well, one of the maxims of E&M is that a static magnetic field does no work. This is because the magnetic force is always transverse to the direction of motion. So it seems to me that this would be pretty difficult. There's certainly room for subtleties here - like maybe the geodynamo mechanism does work for you to keep the field static and that's how the conservation of energy is preserved.