Kelvin - Planck Statement (continued)

Second law restricts the thermal efficiency of a heat engine to less than one. It stipulates that some portion of the energy absorbed as heat from a source must always be rejected to a low temperature sink.

Wilhelm Ostwald introduced the concept of perpetual motion machine of the second kind (PMMSK or PMM2), that is, of a device which would perform work solely by absorbing energy as heat from a body. Such a device does not violate the first law of thermodynamics.

Figure 17.1

A PMMSK is a hypothetical device (Figure 17.1) which working cyclically, receives energy as heat from a single thermal reservoir, and delivers as equivalent amount of work. The Kelvin-Planck statement of the second law tells us that it is impossible to constructs a perpetual motion machine of the second kind.