Doesn't matter which is fixed and which rotates, the output is the same. The only problem is that you need a commutator or brushes to pick off the output from the rotating coil.
"f the copper wire weighs less than the magnet it would require less force" no, weight has nothing to do with force for a rotating object, as long as the bearings are good enough to handle the extra weight. Force only determines how long it takes to accelerate it to the final speed.
Consider that if you spin the copper coils you need brushes to give or harvest the electricity (whether you are using it as a motor or generator), and those brushes will give you losses in the form of friction and electrical resistance. It's better to move a powerful permanent magnet and keep the coils stationary.
And the next logical step is to skip the permanent magnets and generate the magnetic field with copper coils and turn another set of copper coils in it or vice versa, which is also done especially with AC motors.
It already exists and it works fine. Good idea.
Now an electric generator works by rotating a magnet inside coiled copper wire right? So if you reversed that and coiled copper wire around a shaft that rotated and held the wire between the north side of one magnet and the south side of another or one magnet with north and south on each side of the coil would it have the same effect? In theory its all the same so it should but would this be less effective? I only suggest this because I haven't seen anything about it and I have a tendency to try things differently to see I can get better results. If the copper wire weighs less than the magnet it would require less force to generate electricity by rotating the wire therefor it would be more efficient no? Is this something that's been tried?
