part of the process. The integral is to be taken from the initial state to the final state, giving the entropy difference for the forwards part of the process. From the context, it is clear that 1=''N'' = 0 if the process is reversible and ''N'' > 0 in case of an irreversible process.

First and second law

The laws of thermodynamics apply to well-defined systems. Fig. 1 is a general representation of a thermodynamic system.

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