3 replies to this topic

[Spliknot13]

Hi everyone! Just want to ask something about the 2nd Law of Thermodynamics that our professor asked in class.

 

The question goes something like considering a closed Isothermal Process then the change in energy of a system is equal to zero and thefore Q=W so does this violate the 2nd where all of the heat is converted to work?

 

I think we somehow know that it does not violate it but then again we cant really have an answer that fully resolves the question. Ive read something that it can be visualized as a piston cylinder setup where Q can be converted to W as long as the piston is infinitely long and does not need to be reverted back to its original position where some heat will be rejected?

 

Ive been thinking about the question for a long while now and cant come up with a good answer and it totally bothers me. Either way our professor said he doesnt know the explanation to that so Ive posted this. Any help to to answer my inquiry will be pretty much appreciated.

[breizh]

http://processengine...ndamentals.html#

 

Spliknot13

Consider this resource , you may find your answer .

 

Good luck .

Breizh

[shan]

The 2nd law of thermodynamics states that in a natural thermodynamic process, there is an increase in the sum of the entropies of the participating systems. 

The piston moving in the infinite cylinder has not completed a thermodynamic cycle (not return to the initial point).  How do you prove no entropy increase?

[Spliknot13]

@Breizh thanks for the link but after reading again I still fail to come up with an answer

 

@Shan could you explain more please? I did not consider thinking about it in an entropy/cyclic thing since it becomes more confusing for me. The Kelvin Planck statement of no possible cyclic device with 100% efficieny of converting heat into work I think was the statement of the 2nd Law that our professor asked if it was violating it. Is the equation only  theoretically possible for non cyclic devices? like the infinitely expanding piston?