On Mon, 29 Dec 2003 23:04:25 GMT, ATP wrote:

I don't understand why this is not clear to everyone here. Which has more
energy-one liter of 200 psi gas or two liters of 100 psi gas? Can you do
any work going from one state to the other? In one direction you can,

True. There is one catch in this example (and a lot of similar ones in this
thread) though... If you start with one liter of 200 psi gas, and let it
expand through an air motor into a receiving tank until you have two liters
of 100 psi gas, you can extract some work, but you don't end up with those
two liters in the receiving tank.

To accomplish this task you must use a one-liter receiving tank. At the end
of the demonstration, one liter is still in the original source tank,
because the flow stopped when the receiving tank reached 100 psi. Putting
that second liter of air into the source tank cost you more than putting
the first liter in, and more than putting a constant 100 psi against the
motor until the receiving tank was at 100 psi.

Loren