PrinciplesOfThermodynamics 2009-01-07 04:10:36 2009-01-31 10:17:57 Topic overview of the content of PlanetPhysics reversible process open system closed system absolute temperature internal energy entropy state functions thermodynamic principles % this is the default PlanetPhysics preamble. as your knowledge % of TeX increases, you will probably want to edit this, but % it should be fine as is for beginners. % almost certainly you want these \usepackage{amssymb} \usepackage{amsmath} \usepackage{amsfonts} % used for TeXing text within eps files %\usepackage{psfrag} % need this for including graphics (\includegraphics) %\usepackage{graphicx} % for neatly defining theorems and propositions %\usepackage{amsthm} % making logically defined graphics %\usepackage{xypic} % there are many more packages, add them here as you need them % define commands here [This is a contributed entry in progress.] \section{Principles of Thermodynamics} \subsection{Basic Concepts} {Thermodynamic systems}: Closed vs. Open systems. \textbf{Thermodynamic Processes:} Reversible vs. Irreversible := Equilibrium vs. Non-equilibrium \subsection{The Zeroth Principle} \textbf{1. Thermal Equilibrium definition. 2. Temperature is a \emph{measure} of the degree of molecular motion: the higher the average magnitude of velocities in a system measured at equilibrium with the system, the higher the temperature is (the hotter the system is). Absolute temperature scale} \begin{remark} Whereas absolute temperatures of molecular systems can only take on positive values, spin temperature--or spin-lattice temperature-- for example, may take on `negative' values as a result of spin population inversion through polarization, or cross-polarization. Such cross-polarization processes might be thus utilized in designing and operating quantum `computers' or quantum nano-robots. \end{remark} \subsection{The First Principle} \textbf{Total Energy Conservation} \subsection{The Second Principle} During any thermodynamic process the entropy of a closed system always increases if the closed system is not at equilibrium (when the latter becomes constant), [or, equivalently, that perpetual motion machines are impossible]. \subsection{The Third Principle} The entropy of any crystalline system tends to zero in the limit of absolute zero temperature. \subsection{Discussion} Suggested Fourth Principle: \emph{the Onsager reciprocity relations} \textbf{Remark:} Commonly, the four principles of reversible thermodynamics are also known as 'the four thermodynamic laws'.