The First Law of Thermodynamics

Abstract

The results of experiments in which work is done on a system having an adiabatic boundary, for example, Joule’s ‘paddle wheel experiment’, can be summarised in the following statement:

When the state of a closed system is changed from an initial equilibrium state to a final equilibrium state solely by the performance of work, the amount of work needed depends only on the initial and final equilibrium states of the system and not on the means by which the work is performed nor on the intermediate states through which the system passes.