Michel Jullian wrote: > I don't see the COAM violation, the rails would be attached to the > Earth, whose own angular momentum would be (ever so slightly) modified > to conserve AM of course. > > If you added to the setup I described an externally generated magnetic > field going through the track, the ball would go round the track > wouldn't it, would this be a COAM violation?
In the setup you described in your previous note there was no such external field. Absent the external field there's no interaction with the Earth or the track which could offload the angular momentum, and yes, you would have a violation. If you disagree please explain how the AM transfer to the Earth or the rails happens, with *no* externally applied field. Of course, if there WERE an external field, then the ball would be driven around the track, for it would be a homopolar motor, which is well understood. But so what? That has nothing to do with the case of the BB motor, where there is no external field. (That's kind of the point.) I really don't see what you're getting at here. > > Michel > > 2009/8/25 Stephen A. Lawrence <[email protected]>: >> >> Michel Jullian wrote: >>> Good point, it would make it unidirectional, if not necessarily >>> self-starting (dynamic friction is lower than static friction). So any >>> magnetic field at play must be self generated. >>> >>> I wonder, would a ball put across two horizontal, static and >>> concentric circular rails rotate by circulating current through it via >>> the rails? If it did, this would invalidate your theory wouldn't it? >> Would violate COAM too if I understand what you're proposing. >> >> So, no, it wouldn't rotate. >> >> >>> Michel >>> >>> 2009/8/24 Stephen A. Lawrence <[email protected]>: >>>> Michel Jullian wrote: >>>>> There may be another cause for a net B field through the ring: the >>>>> Earth's. (apologies if this was mentioned before, haven't followed the >>>>> discussion closely) >>>> Too weak to be significant, almost certainly, but more to the point a >>>> fixed field through the ring would make the motor unidirectional and >>>> self-starting. It's neither. >>>> >>>> >>> >> > >
