15.6 The Second Law
The nature of heat energy as found in the Carnot Cycle operation is such that it cannot be
completely converted into mechanical energy since it is a cyclic operations. This observation is universally true,
i.e. independent of the design of the engine and the nature of the working substance.
This observation therefore becomes a law of nature called The Second Law of Thermodynamics. It
was formulated by Kelvin and Claussius in different but similar statements. According to Kelvin: "No
heat engine can be designed which can convert completely all heat energy from a reservoir into
mechanical energy without producing any changes in the surroundings." According to Claussius: "It is impossible
to cool any object below the coldest object in the surroundings."
The Second Law of Thermodynamics has been formulated in various
forms, which are equivalent to each other.
It is impossible to cool an object below the coldest object in its surroundings, without producing
any changes in the surroundings.
It is impossible to transfer heat from a lower to a higher temperature without producing any changes in
No heat engine can be designed which can convert heat from
a single reservoir completely into mechanical energy.