Has a suitably constructed (magnetic steel?) slip ring been shown not to produce the effect?
On Fri, Aug 21, 2009 at 5:42 AM, Stephen A. Lawrence <sa...@pobox.com>wrote: > > > Horace Heffner wrote: > > >> > >> It's hard to see how AM balances; that's true. However, take a look at > >> the attached jpeg, which is a much simpler system: > >> > >> It's a set of ball bearings in a race, just as you've been using. The > >> balls are assumed to be NON-MAGNETIC. In fact, the balls may be assumed > >> to be FLAT DISKS, which will make this simpler in some ways (make 'em > >> planetary gears if that's easier to picture). > >> > >> The blue "current loop" is just that: it's a current loop, current > >> going clockwise, which provides a magnetic field, which goes "up" > >> outside the loop and "down" inside the loop, indicated with "o"s and > >> "x"s. If the "balls" are flat disks this is easy to do; if they're > >> actually 3-d balls it's a little harder but the basic field arrangement > >> is surely realizable. > >> > >> There is current through the balls, going radially out, as shown. > >> > >> Surely there is a TORQUE on each ball, just as in your "model" of the > >> ball bearing motor. This sort of thing is practical to realize; it > >> strikes me as a simple variant on the homopolar motor but I haven't > >> thought about the comparison a lot. > >> > >> So.... WHY IS ANGULAR MOMENTUM CONSERVED IN THIS CASE? > > > > > > I think the answer is that there is a return current segment (or are > > current segments) not shown that goes from the outside race to the > > inside race. If the sum of the ball currents is N*i = 5*i then the > > return current is also exactly N*i. The torques exactly cancel. What > > you have are two independent circuits acting on each other, which is > > well known not to violate COAM. > > > But isn't the situation identical with the BB motor? > > You have a magnetic field within the bearing which has similar topology > to the field provided by the current loop in my diagram. > > It's an ordinary magnetic field, and no matter what its cause, it must > also have the usual properties of B-fields: The field lines never end, > they just form loops. > > And you've got current going all the way around -- there is a current > return path somewhere, outside the bearing, which you haven't shown. > > Even if (part of) your return path goes through a second bearing at the > other end of the motor, you're still in the realm of something which can > be simulated with my little current loop -- you just need a second loop > for the second bearing (with current going CCW in the second loop). And > when you try to think about what the fields must look like outside the > two bearings in my "gedanken", you're also thinking about what the > fields must look like outside the two bearings of a BB motor, because > once again, the fields have roughly the same "shape". > > So, you may need to look to the *wires* bringing current to the motor, > and their interaction with the B-field produced by the spinning ball > bearings, to figure out where the "balancing" part of the angular > momentum equation is. And you may also need to look at the current > flowing ALONG THE SHAFT, where the B field lines from the bearings are > curving around, so that the current in the shaft is *not* parallel to > the B field lines, and there will consequently be a Lorentz force on it. > > > > > > >> > >> I don't see it, off the top of my head. But it surely is, and whatever > >> the mechanism, the same thing may be at work in the ball bearing motor. > >> > >> For that matter COAM in the case of the homopolar motor is pretty hard > >> to sort out, too!<horace-ball-bearing-motor-1.jpg> > > > > Best regards, > > > > Horace Heffner > > http://www.mtaonline.net/~hheffner/<http://www.mtaonline.net/%7Ehheffner/> > > > > > > > > > >
