# Efficieciency

Discussion in 'Electronic Basics' started by [email protected], Jul 1, 2007.

1. ### Guest

Hello everybody,
I am new in here and i am a 6th grader. i wonder if u could help me.
U see i have been asked for a couple of times that why can't we build
a 100% efficiency power electonic generator. Hope you can help me.

From

2. ### EeyoreGuest

Think about electrical resistance and the effect it has.

Graham

3. ### John PopelishGuest

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.

4. ### CharlesGuest

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)

5. ### AlyGuest

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.

6. ### Jasen BettsGuest

electrical resistance
friction
leaking magnetism

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

7. ### neon

1,325
0
Oct 21, 2006
if you do that let me know you are the first humanoid to biuld the perpetual moving machine. moron