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Is this a "good" experiment:It is not a good experiment, in one respect.
A well insulated cylinder with a low thermal mass and conductivity piston. The top of the piston's con rod, instead of a handle, has a weight cup. (included P and T sensors)We may visualize this continuous process approximately, with a series of weights stationed between the starting position of the cup and piston, and its lower final position.
Trial A; continuously and slowly add small weights 'till the V is, say, 1/10 the original.
Trial B dump the weights in all at once (a single weight = in mass to the above ones)We may visualize this discrete process by adding the sum of the weights mentioned in Trial A all at the highest position mentioned in Trial A
discussion: P and T and from the discussion S will differ, but the work mgh will be the same. Is this experiment at least qualitatively possible and instructive?I ask you to consider the potential energy contributed in Trial A to the potential energy contributed in Trial B.
bc prays he's not all wet here.
/snip/Brian W
On 2010, Jan 17, , at 17:10, John Mallinckrodt wrote:
...assume a) that the gas is thermally insulated, b) that it starts and ends in thermal equilibrium, and c) that the initial state is given.
CASE 1: An irreversible compression to a given final volume, (i.e. Carl's case):
1. Stirring has occurred and the final entropy is greater than the initial entropy. (Because we are explicitly told that the process is irreversible.)
2. The final energy is greater than it would have been had the process not been irreversible. (Because higher entropy => higher temperature => higher energy for a given volume.)
3. More work was done on the gas than would have been had the process not been irreversible. (Because the extra energy was entirely the result of extra work done.)