Efficieciency

Think about electrical resistance and the effect it has.

Graham

Generators do not produce energy, they convert mechanical energy to electrical energy. Every conversion process includes some wasted energy. For instance, just spinning the rotor of the generator involves the drag of air on the rotating part, and the friction in the bearings.

Operating the generator in a vacuum would eliminate the loss to air drag, as a possible improvement, but the air also helps to carry away the heat produced by current passing through resistance of the generator windings. The hotter the windings get, the higher their resistance, so the more energy is wasted in that part of the process. So eliminating the air in the generator makes one loss lower, and one higher. Good engineering involves optimizing the overall blend of losses, so that the overall efficiency is maximized. But 100% is never possible.

You might have to get into the physics of irreversible processes to put that fact on a mathematical basis.

I'll assume that you mean an electric generator that is a rotating machine. Turning the shaft means that one must overcome bearing friction ... that's only one loss which precludes 100% efficiency. Other losses are:

resistance loss in the coils/windings magnetic losses in the iron cores of the rotor and stator (eddy currents and hysteresis loss). air resistance (as it rotates, it is obliged to shove air molecules aside)

For God's sake don't answer the exam questions in text speak. Sort out your spelling too.

While I've never ascended (descended?) to the level of NetNanny, if you are looking for advice then it applies here.

YOU WILL lose marks. Language is above everything.

Oh, and we can't build a 100% efficency power electronic generator as we do not live in a perfect world. I could mention Tesla but that's something for another time.

electrical resistance friction leaking magnetism

beat those three and you'd probably be able to do it.