Hello. I looked for information about how the homopolar generator works, because there are some claims (N-machine, Space Power Generator...) that say there is no backEMF or opposition to obtain the work. The homopolar generator is a disc magnet glued to a conductor disc. When you make it turn, there is a EMF between the axis and the periphery of the discs. Well, we usually explain the working of the motors saying that a change of magnetic flux causes a current on coils. The magnetic flux change is the method we normally use to move the electrons. On the homopolar generator, the magnet does not impulse or move the electrons of the disc. A motor moves the disc and the magnet, so the electrons of the disc move. The only difference with normal motors is the method to impulse the electrons. The homopolar generator does not use the relative movement respect the magnet, it uses the relative movement respect the motor. On this page there is better explained all the forces and energies involved (sorry, in Spanish, but the drawings and the formulas should help): www.sc.ehu.es/sbweb/fisica/elecmagnet/induccion/homopolar/homopolar.htm Well, finally it's stated that it's just like the linear version of the experiment, but on a rotary fashion. But i'm not so sure. My question is about the current supposed to run on the radius of the disc, that is supposed to create the opposite torque to the motor. On the linear device, the electrons that run through the rod creating the current are the same electrons (they have PERPENDICULAR velocity to the path, but they feel an EMF ALONG the path, and they move in a current ALONG the path, so they finally create backdrag also). But in the homopolar generator, every moment, the electrons that creates the EMF from the radius of the disc are different ones (they have a velocity PERPENDICULAR to the radius, so they feel an EMF ALONG the radius, but they finally move PERPENDICULAR to the radius). My question is: Stated that the electrons on the radius are not the same every time step on the rotary disc, can we consider that it is a real current?, is really a current running through the disc radius?