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Re: [Phys-l] T dS versus dQ

Is this a "good" experiment:

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)

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)

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?

bc prays he's not all wet here.

p.s. in lit. searching the Clément and Desormes experiment, I discovered Clément married his friend and colleague's daughter and became Nicolas Clément-Desormes

On 2010, Jan 17, , at 17:10, John Mallinckrodt wrote:

Now some cases. In each, I 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

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.)