Your question is vague. Output power = force times distance divided by time. Motor characteristics are a product of the type and
there are many. Generally the efficiency of a motor can be determined by the temperature rise in use. The hotter the motor gets,
the less efficient it is. However when using AC motors, the power factor should be considered as well, as it will identify
electric energy drawn, but not used. I think the motor you are identifying is a DC motor. Some DC motors will run on DC or AC.
They make their own AC with the commutator and brushes, like electric drill and vacuum cleaner motors. I think you should ask the
root question you have and give us specifics.
Steve

"Michael Koblic" wrote in message ...
I have been trying to work this out from basic principles but the answers are at best foggy:

Consider two electric motors (commutator) with identical inputs, say 250W, and identical RPM, say 15,000. What are the factors
that determine the motor efficiency and thus the output power?

If I understand the physics, the output power is directly related to torque if rpm are held constant. What then, in the nature
of the motor construction, will increase its torque? Is the diameter of the rotor one of the factors?

Thanks,

--
Michael Koblic,
Campbell River, BC