2018/03/26 by P. D. Gujrati, Gujrati, P. D.
Engineering · Physics and Astronomy · #Advanced Thermodynamics and Statistical Mechanics #FOS: Physical sciences #Phase Equilibria and Thermodynamics #Quantum Mechanics and Applications #Statistical Mechanics (cond-mat.stat-mech) #cond-mat.stat-mech
paper · pdf · doi:10.48550/arxiv.1803.09725
20 pages, 4 Figures. Some overlap with arXiv:1702.00455
openalex publication_date 2018/03/26 · arxiv created 2018/03/28 · arxiv updated 2018/03/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The energy change dEk for the kth microstate is erroneously equated with the external work done on the microstate. It ignores the ubiquitous internal energy change diWk due to force imbalance between the internal and external forces. We show that this contribution is present even in a reversible process, which is a surprise. We show that the correct identification is dEk=-dWk, where dWk is the generalized work done by the microstate. We prove that the thermodynamic average of the internal work gives dissipation and is not captured by the external work. The latter effectively sets diWk =0 and results in no dissipation. Using dWk to account for irreversibility, we obtain a new work relation that works even for free expansion, where the Jarzynski equality fails. In the new work relation, dWk depends only on the energies of the initial and final states and not on the actual process. This makes the new relation very different from the Jarzynski equality. The correction has far-reaching consequences and requires reassessment of current applications of external work in theoretical physics.