How can a rotating wheel stop using magnetic power? For example, consider a rotating iron wheel: can it be made to stop suddenly with using magnetic power? If so, how?
By Lenz's law the direction of the current induced in a conductor (your iron wheel) by a changing magnetic field (the rotating iron wheel between magnet's poles feels a changing magnetic field relative to it) is such that the magnetic field created by the induced current opposes the initial changing magnetic field.
Or, more vaguely, the induced current opposes the change which induced it.
So the result is that the wheel will eventually stop (= no more change in a magnetic field).