I know the magnetic field makes a circle around a wire with current flowing through it. So I wondered if a motor could be made in the following way. Take a round plastic sleeve with an inner diameter slightly more than the wire. Glue 4 magnets on the sleeve, such that they form a circular magnetic field (for example, the north pole of each magnet could always face to the right when looking down at the vertical sleeve from above). Now run the wire through the sleeve and allow current to flow. It seems to me that there will always be a constant net force on each magnet, resulting in a constant torque to spin the motor. But some things don't seem right about this. As the motor spins, it appears to me that the magnetic flux experienced by the wire is not changing. Thus, there will be no back EMF generated to limit the speed of the motor. So the motor could reach infinite speed (neglecting friction). For the same reason, the device could not be used as a generator, which seems strange from a symmetry perspective. What is wrong with my idea? I know from a practical standpoint the current in the wire would have to be high, since there is only a single wire involved vs. the multiple turns in a conventional motor. But in theory, would this device work?