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Session 2268

Meandering Road from Dynamics to Thermodynamics and Vice Versa: What Is Work?

Ing-Chang Jong, Rick J. Couvillion, Larry A. Roe University of Arkansas

Abstract

The science of mechanics may trace back to Aristotle (384-322 B.C.) and Archimedes (c. 287-212 B.C.), while thermal science may trace back to the steam engines by Savery in 1697 and New- comen in 1712 or to the works of Rankine, Clausius, and Lord Kelvin in the 1850s. Both are old sciences where, from time to time, definitions formulated for terms to serve the purpose of pre- vious existing physical understanding are later found inadequate, incorrect, or inconvenient for the description of more complete modern knowledge. Some definitions and conventions in dynamics and thermodynamics are given differently and can be confusing to unsuspecting undergraduate students who are taking them in their curricula. To a certain extent, this is the case with the terms heat, work, potential energy, and conservation of energy. This paper is aimed at pointing out the curvy and bumpy stretches on the road from dynamics to thermodynamics, and vice versa. It is hoped that better inter-disciplinary understanding will enhance effective communication for in- structors and better learning for engineering students.

I. Concepts of Process, Path, and Heat

A process is any change (or transformation) that a system undergoes from one state to another. The series of states through which a system passes during a process is called the path of the process. To describe a process completely in thermodynamics, one needs to specify the initial and final states of the process, the path it follows, and the interactions with the surroundings. A quasi-static, or quasi-equilibrium, process is one which proceeds in such a way that the system remains infinitely close to an equilibrium state all the time.

The old caloric theory asserts that heat is a fluid-like substance called caloric, which is a mass- less, colorless, and tasteless substance that can be transferred from one body into another body to increase the temperature of the latter. This theory came under attack soon after its introduc- tion by the French chemist Antonie Lavoisier (1743-1794). In 1798, Count Rumford (1753- 1814) showed in his paper that heat can be “generated” continuously through friction. It was only after the careful experiments of James P. Joule (1818-1889), published in 1843, that the true physical nature of heat was understood through the kinetic theory. This theory treats molecules as tiny balls that are in motion and thus possess kinetic energy. Joule convinced the skeptics that heat was not a substance after all. Heat was then defined as the energy associated with the kinetic energy of the random motion of atoms and molecules. Although the caloric theory was totally

Proceedings of the 2002 American Society for Engineering Education Annual Conference & Exposition Copyright © 2002, American Society for Engineering Education

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Couvillion, R. J., & Roe, L. A., & Jong, I. (2002, June), Meandering Road From Dynamics To Thermodynamics And Vice Versa: What Is Work? Paper presented at 2002 Annual Conference, Montreal, Canada. 10.18260/1-2--11242