
38 The Principles of Thermodynamics
changeable; obviously, this marks a fundamental departure from Carnot, who based
his Reflections on the premise that heat can neither be created nor destroyed. There-
fore, according to Clausius, at the end of a reversible cycle the net amount of heat
absorbed must equal the net work performed, i.e ΔQ =ΔW, whereas for Carnot
ΔQ =0while ΔW =0.
FIGURE 2.3 A Carnot cycle
Almost everything else follows just from this initial departure, which is of course
a very radical departure. It is immediately obvious that heat can not be a state func-
tion as was the case in the caloric theory. If it were, dQ would have been a perfect ...