Work performed by a Classical-"reversible"-Carnot cycle: Raising's distribution for the small "driving weights"

Abstract

The expansions or the compressions of the ideal gas in the quasi-static Carnot cycle, can be performed (on adiabatic or isothermal way) by slowly increasing or decreasing the external pressure by means of small weights acting on the piston of the vessel containing the gas. We call them shortly the ``driving weights'' (dw). Let N be their number, a large one. To determine the work performed by the ideal gas in the cycle the ``driving weights'' must be handled carefully. If we let them move on-off the piston only horizontally, their vertical motions will be due only to the gas. Here we show that, at the end, while some of them will have moved down (will have negative raising) the remaining ones (the majority) will have moved up (will have positive raising) so that the total work performed by the ideal gas equals the total variation of the gravitational potential energy of the ``driving weghts''. The cycle is performed in 2N time-steps. For each step t_i, with i in 1,..,2N, we give H(t_i), and DH(t_{i-1},t_i), respectively the height and the raising of the piston. Moreover the overall raising of the individual dw's (i.e. h_k, with k in 1...N), and their distribution are given in simple, general cases. The efficiency and the dissipated work are also evaluated. This paper is aimed at imparting a deeper understanding of the ideal Carnot Engine and may also be useful as a segment in a didactic path on elementary calculus and statistics.