Kinetic characterization of heat bath and the energetics of thermal ratchet models

Langevin equations have been employed to describe thermally fluctuating systems, such as thermal ratchet models. Their role of the heat bath in these contexts has not keen clearly understood. We introduce an approach to this issue and, by using it, propose a method to study the energetics of those models. As a example, we calculate the efficiency of energy conversion of ''Feynman's ratchet''.