Heat Engines and the Laws of Thermodynamics

Abstract

The first law of thermodynamics states that mechanical energy and heat are mutually convertible, the total energy remaining constant. Now, we have been developing a picture of heat as that form of mechanical energy in which the energy is shared among a great many independently moving particles, indeed among the independent “degrees of freedom” of those particles. It seems reasonable, therefore, that when energy is transformed from the energy of organized mechanical motion (normally referred to by us as “mechanical energy”) to the energy of disorganized motion that we call heat, the transformation should be on the basis of a joule for a joule (or one calorie for 4.18 joules, where the calorie is a unit based on the properties of water). If one joule of mechanical energy is transformed to heat, it should become one joule of heat. If one joule of heat energy is transformed to mechanical energy, it should become one joule of mechanical energy.