Abstract
According to Sommerfeld, the well known Clausius and Kelvin statements of the second law of thermodynamics comprises two parts. The first part includes the Carnot principle that all Carnot engines operating between the same temperatures have the same efficiency. The second part contains the law of increase in entropy. Usually, the two parts are understood as a logical consequence of these statements, including the Carnot principle. Here, we argue that this principle need not be a derived law and may be considered as a fundamental law, without the need of demonstration. To this end we analyze the roots of the second law, which are contained in the memoir of Carnot on the production of work by heat, and its emergence in the papers of Clausius on heat.
Keywords:
thermodynamics; second law of thermodynamics; Carnot principle; Clausius principle