A system can be taken from the initial state p1, V1 to the final state p2, V2 by two different methods. Let ΔQ and ΔW represent the heat given to the system and the work done by the system. Which of the following must be the same in both the methods?

According to First law of thermodynamics,


ΔQ=ΔU+ΔW


Where ΔQ=heat supplied/extracted to/from the system


ΔU=change in internal energy


ΔW=work done by/on the system


ΔU=ΔQ – ΔW


It is given that initial state (p1, V1) and final state (p2, V2) is same for both the method.


So, change in internal energy will be the same for both the methods as internal energy is a state variable and is independent of the path taken to achieve a state.

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