A. Peltier Effect: Heating or cooling a junction by electric current.Carnot's original cycle involves heat transformation between a hot TH bath and a cold TC bath by a gas in acylinder equipped with a moving piston. Heat partly flows from a hot bath to a cold bath, and partly istransformed to mechanical work in a reversible four step closed cycle. Carnot knew nothing about thechemical potential, not even about entropy, since both of them belonged to the far future in his time. Neverthe less, he correctly analyzed his cycle without these terms. At each step of the cycle macroscopicmechanical work of the moving piston is transformed to microscopic thermal movement of the gas particlesby elastic collisions between the particles and the piston [9].Similarly, the macroscopic electrical work of a power source is transformed in a junction to microscopicthermal heat by acceleration of charge carriers in the electric field. Electrons that cross a junction will beeither slowed, or accelerated by a contact potential difference Vc according to the directions of theirvelocity vector relative the electric field. Thus, they will absorb or deliver an amount of heat eVc to thejunction, where Vc is given by eq. (7). Peltier coefficients (2) are then: