Finally, comparison for the both representations of a work output in a Carnot cycle gives us: | Q H | T H − − | Q C | T C = Q H T H + Q C T C = 0 Similarly to the derivation of internal energy, this equality implies existence of a state function S with a change of d S = δ δ Q / T and which is conserved over an entire cycle. Clausius called this state function entropy.