Thermodynamics

State−1

Expansion

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State−2
(p1,V1,T1)    (p2,V2,T2)
⇒Work done in reversible compression process is smaller than the work done in irreversible compression process
⇒ ΔU=0 for reversible isothermal expansion.
ΔU<0 for reversible adiabatic expansion.
⇒ For free expansion q=0,w=0 and ΔU=0 hence it is simultaneously both isothermal (ΔU=0) as well as adiabatic (q = 0).
⇒ Work done in reversible adiabatic expansion is less than the work done in reversible isothermal expansion as shown in figure