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/ > > > >
