Re: Is it possible to have an electric motor that has only one pole?

Jacob,

There are several reasons that motor efficiencies change with angular 
velocity of the rotor. You are correct that the interaction of the 
magnetic fields of the rotor and stator is one source of inefficiency, 
both from the energy losses in expanding and collapsing the fields and in 
small variations in timing the interactions of those fields. Other 
sources of efficiency loss are bearing and bushing friction, resonances 
in the motor at different rotational frequencies, and the natural 
property of spinning machinery to have a speed where power transfer i 
most efficient.

Your thought of having a single magnetic pole is an interesting one, but 
so far no one has observed a single-pole magnetic field: they always 
occur in north-south pairs. It is possible to align the poles in a magnet 
so that all the same-polarity poles of the stator point, but half the 
energy stored in the magnetic field of the motor would be wasted, doing 
no work because it isn't interacting with the rotor. Imperfections aside, 
it's far more efficient to use both poles of the field.

I hope this helps!