-- Both devices have mechanical processes going on OUTside,
and electrical and magnetic processes going on INside.
-- Electric motors are intended to accept electrical energy as their
input, and to deliver useful mechanical energy as their output.
-- Electric generators are intended to accept mechanical energy as
their input, and to deliver useful electrical energy as their output.
Depending on their internal design, some styles of each device
can be used "backwards", to function as the other one.
