Thermodynamic Systems and Cyclic Processes

Abstract

The first law of thermodynamics, as stated in the previous chapter, relates heat and work. In addition, it makes possible the definition of stored energy. According to this law, as long as the energy is conserved, any process is possible; there are no restrictions as to which way a process will go. Up to this point, it has been tacitly assumed that any process could go in any direction. Thus, if restricted only by the first law, a power plant could be operated by taking energy out of the air, and a ship could cross the ocean by extracting energy from the water. However, experience suggests that this is not the way the world is. Although it is not impossible to get energy from these sources, it requires an energy input. In general, nature is such that you cannot get something for nothing. (In fact, you do not break even.)