Little belated here -- didn't notice this initially. Horace Heffner wrote: > > On Aug 9, 2009, at 4:37 PM, Kyle Mcallister wrote: > > >> I still find the motor interesting, because everyone wrote it off as >> a thermal thing. This seems, as you suspect, to be magnetic, albeit >> in a different way than expected. It also dumbfounds people I show it >> to, so that's a nice plus. :) > > Well, Kyle, the ball bearing motor may just have some anomalies left > up its sleeves. Looks like the back emf possibly doesn't increase > with rpms, at least in some range. How strange is that? > > And then there is the major fact it can't be run backwards to generate > electricity! Where's the symmetry!?
I'm not at all sure this is correct. The experiment hasn't been tried (or even designed, really). A generator which powers its own field windings won't self start, right? You can spin it until you're blue in the face but nothing will happen, unless you apply some external power to it to energize the field windings and get it going. Once it's going you can take away your external power source, of course. (Of course if there's "residual magnetism" stuck in the iron core of the field windings, that may be enough to get it going -- but a brand new one, right out of the box, won't self start the first time it's used.) This may be the same deal. You spin a bearing, and nothing happens. Well, maybe if you apply external mechanical power /and/ you run a current through it to get it started, it will start generating electricity on its own. But even with a jump start, it may be that the electricity it generates just isn't sufficient to power its own "field windings", wherever they may be.... considering how inefficient the thing is when operating as a motor, that wouldn't be all that surprising, actually.
