Electricity

[ERICK84]

Why is it that electrical power cannot be used to power turbines which can in turn produce electricity and perhaps cycle maintained?

[tigersam258]

because the amount of power required to get it going would negate the power achieved.

[jake-the-peg]

Conservation of Energy

It can only be converted from one form to another.

There is a long (and funnny) history of perpetual motion machines.

Most recently the fraudsters who'll tell you that cars can run on water.

here's a few of the others:

http://www.lhup.edu/~dsimanek/museum/people/pe ople.htm

Even the otherwise great Leonardo had a scheme

[dundurn]

When too much electricity is produced in the National Grid there are some hydro-electric schemes which operate in reverse. Water is pumped back up the hill to be used again when demand justifies it. This is using the water supply something like a battery. As the previous answers have said, however, there is an inefficiency at each stage in the process and you don't get back out what you put in.

[sp1214]

Surely wave and wind power are examples of perpetual motion.

[gen2]

No sp1214. With wind and waves, there is a constant input of fresh energy - the sun.

Any energy derived from wind or waves has originally come from solar energy. When the sun runs out of energy, I'm afraid we've had it.

[gen2]

May I also add something that nobody else has mentioned yet - namely that in the example given, friction causes energy to be lost, mostly in the form of heat and some in the form of sound. That is why you will never get out of the system as much electrical energy as you put in.

[New Judge]

Just to be pedantic, you need to be a little careful when discussing wave power. Some systems generate power from the vertical surface movements of waves. These do indeed rely principally (though not entirely) on the Sun�s energy creating winds and the winds producing waves.

However, many proposals for power from the sea (and indeed one that has been operational for some years across the Rance estuary in France) rely on the movement of the tides. Tides are produced as a result of the interaction between the Earth�s rotation and the moon orbiting the Earth. Energy captured by these methods is at the expense of the Earth�s rotational speed and any such schemes will imperceptibly slow down the planet�s rotation and increase the length of the day.

Because of the tidal effect the Earth�s rotation is slowing down anyway and at some time in the future the Earth and moon will become �tidally locked�. This means that the Earth�s period of rotation will equal the time taken for the moon to orbit the Earth. (This has already happened to the moon, which is why we only ever see one side of it).

When this happens there will no longer be any tides. Whether this will be before or after the Sun runs out of energy I don�t know. However, before the Sun does eventually die entirely it will expand into a �Red Giant�, engulfing the planets as far as Earth and possibly Mars, so the question may be academic.

[sp1214]

If the Earth does stop rotating I'd hate to be on the dark side.

[New Judge]

No, I did not say the Earth will stop rotating. It will still rotate (althought its rate of rotation is decreasing - the length of the day is increasing).

At present the Earth takes one day to rotate on its axis and the moon takes 28 days to orbit the Earth. Eventually these two periods will coincide and the same part of the earth will always face the moon. This is evident with the moon - it takes 28 days to orbit the Earth and the same amount of time to rotate on its axis. When this happens there will no longer be any tides in the sea.

[Peter Pedant]

This is a good question

I am surprised that no0-one has said that this little plan of your falls foul of the 2nd Law of Thermodynamics -you can't even break even

IN this case the friction in the machines will ensure that conversion is less than 100%

So there is always a bit lost as heat.
Surprising bit is, that there is always a bit lost as heat no matter what the transaction

Sadi Carnot was the first to prove this in 1895 and DIDN't use the first law, in order to do so

[sp1214]

I suppose hybrid cars are trying to get close to p.m. I have heard of a couple of wacky ideas. Just a few years ago an air inlet under the car forced a spindle to rotate and generate extra electricity. The other idea was to install in the road a form of dynamo which charged up using the passing cars.

[Toureman]

Marvelous SP1214, you are a genius.

Perhaps you could explain how hybrid cars are powered by by perpetual motion?