Michel Jullian wrote: > Your new experiment (attraction rather than alignment) simplifies things somehow (no torque, just linear acceleration), but let's stick to the non-wire-resistive loop shall we, it makes things simpler, and closer to the electron orbit or spin counterpart you are comparing it to. > > 1/ Using an external current source, let's start a constant current through the loop. > > 2/ Zero wire resistance, zero radiation resistance,
I would question that such a thing is even theoretically possible for an electro-magnet. Perhaps it is possible in another reality where light travels instantly and hence no far field. Or perhaps if the electro-magnets entire closed loop is a 1-dimensional point, but how do you have a closed "loop" with zero length. At best it could be another reality, but not our reality. > constant current so zero auto-induced voltage -L*di/dt, so zero voltage drop. This means we can connect the loop back on itself and remove the current source without stopping the current ok? Let's do that, so that loop voltage will remain zero for ever, and define this as time zero for the energy balance. > > 3/ Now let's release the magnet. It should indeed be attracted and accelerated towards the short-circuited current loop so KE will be gained, but how could the energy be drawn from the loop if voltage is zero? Michel, for the most part the amount of energy contained in the current loop depends on its inductance and current. That is what maintains the current. The current decay depends on resistance, which you say is zero (no wire or radiation resistance). So in your example the current would remain constant if left alone. There are other minor factors, but by far that's the main factor. As the magnet accelerates (angularly or linearly) to the current loop it produces an opposing voltage in such current loop, which decreases the current loops current. During that span of time such opposing voltage is "resistance" on the current loop, as indeed it removes energy from the current loop. If the two objects continue to accelerate long enough then the current loops current will decay to zero amps. In such a case the two objects are no longer magnetically attracted, but they will continue to move depending how much momentum is left, which will generate negative current in the current loop. This will cause the two objects to repel, and you end up with two objects oscillating back and forth *until* the energy is dissipated, which will happen. During each oscillation the electro-magnet could use such gain KE from the current loop as it so desires. It could store such energy in a battery for example, in which case the two objects would quickly slow down until all the energy is removed from the current loop. The longest the two objects could oscillate would depend how much energy is radiated simply from the two objects moving in space. A moving magnetic field generates radiation. So as you can see, energy is indeed moved from one source to the next at the moment it is required. No magical PE required. :-) Regards, Paul Lowrance ____________________________________________________________________________________ 8:00? 8:25? 8:40? Find a flick in no time with the Yahoo! Search movie showtime shortcut. http://tools.search.yahoo.com/shortcuts/#news
