Entropy, Reversibility, Irreversibility and Thermodynamic Cycles

D. Sands and J. Dunning-Davies
Department of Physics,
University of Hull,
Hull HU6 7RX, England.
Email: d.sands@hull.ac.uk
email: j.dunning-davies@hull.ac.uk

Abstract. Following thoughts occasioned by the writings of Tait during the nineteenth century, attention here returns to the importance of cycles in the development of thermodynamics. Considering its practically-based beginnings, it sometimes seems surprising that so many students experience so much difficulty with this subject. Some, at least, of the confusion seems to arise through the introduction of the notion of entropy into the development of the subject – this the one quantity to which, within thermodynamics, it is difficult to give a physical interpretation. In this article, the development of thermodynamics is reviewed in an attempt to highlight the problems arising and offer some insight into their possible resolution. Problems associated with terms such as reversibility and irreversibility are addressed also and, once again, attention is drawn to those extremely lucid writings of earlier years.