The Mayer-Joule Principle: The Foundation of the First Law of Thermodynamics

Abstract

To most students today the mechanical equivalent of heat, called the Mayer-Joule principle, is simply a way to convert from calories to joules and vice versa. However, in linking work and heat—once thought to be disjointed concepts—it goes far beyond unit conversion. Heat had eluded understanding for two centuries after Galileo Galilei constructed an early thermometer. Independently, Julius Robert Mayer and James Prescott Joule found the connection between heat and work, the Mayer-Joule principle.

Isothermal heating: purist and utilitarian views

“…Ultimately, through the research of Mayer, Joule, Colding, and others [3,16], it became clear that heat, like work, is an energy transfer process, and that the total energy in any process is conserved, a revelation that led to the first law of thermodynamics. Notably, the development of the internal energy state function enabled a definition of heat that is independent of the assumption that heating requires a temperature difference.…”

“…To be precise, the temperature difference description is not a complete definition. To fully define the energy Q gained by a gas during a process, one can first define the calorie using water as a standard and then use the mechanical equivalent of heat to link the calorie with the joule [3]. The latter step is a subtle way to define the thermodynamic quantity heat in terms of work, a purely mechanical entity.…”

Name the experiment! Interpreting thermodynamic derivatives as thought experiments

“…We have talked about entropy and the concept of adiabatic processes as quasi-static processes in which there is no heat exchange and the entropy is held fixed. Finally, students have been presented the first law of thermodynamics-the change in the internal energy of a system is the sum of the energy added to it by heating, plus the energy provided by doing work on it: [12][13][14]…”

“…In the same first activity in which we do simple derivatives, as described in the previous section, we also include derivatives that require the use of the first law. [12][13][14] One of the first-law derivatives from Table I is…”

A Link between Nano- and Classical Thermodynamics: Dissipation Analysis (The Entropy Generation Approach in Nano-Thermodynamics)

“…Indeed, during the 19th century, thermodynamics began its development as a physical science as a result of the studies of Sadi Carnot (1796-1832), Julius Robert von Mayer (1814-1878), Hermann Helmholtz (1821-1894), William Thomson (1824Thomson ( -1907 and Rudolf Clausius (1822-1888). But Helmholtz was the scientist who first determine the cultural profile of the thermodynamic researches [70][71][72]. Clausius, just developing the results of Helmholtz and Carnot, published the first formulation of the second law, as we know it today.…”