Joule's Expansion & Entropy Production

[hyperickz]

We all know that in free expansion of gases under adiabatic condition and keeping the temperture constant ,we get that no work is done by the gas.Moreover since del(Q)=0, del(U)=0 according to first law of thermodynamics.But we get a increase of entropy by an amount Rln2.Now the question is that from where does the unavailable energy associated with entropy i.e. Tdel(S)=RTln 2 comes from ?

 

[Suraj M]

We all know that in free expansion of gases under adiabatic condition and keeping the temperture constant

Is this possible?

 

[hyperickz]

Is this possible?

Yes,its possible
Check this:
http://en.m.wikipedia.org/wiki/Joule_expansion

 

[Suraj M]

joule thompson effect does not take place isothermally.

 

[hyperickz]

Its not joule thomson effect.Its free expansion of ideal gas during which temperature remains same due to perfect thermal isolation

 

[Suraj M]

thermal isolation provides only adiabatic conditions not isothermal, for the gas to expand and still maintain its temperature you'll have to supply heat energy.
bottom line, the process you are referring to cannot be isothermal.