When teaching thermal physics and statistical mechanics the authors find a lot of confusion among students about the meaning of the chemical potential μ. It seems particularly difficult for students to develop a physical picture of what μ is. In this paper some simple, pedagogical models are developed to make the meaning of μ clear, for a few selected systems.
Heat and efficiency calculations for negatively sloping, straight-line paths in PV diagrams seem to be consistently misleading or incorrect in many introductory physics texts. The source of the error is identified and thoroughly explored with several examples.
Clockwise cycles on PV diagrams always represent heat engines. It is therefore tempting to assume that counterclockwise cycles always represent refrigerators. This common assumption is incorrect: most counterclockwise cycles cannot be refrigerators. This surprising result is explored here for quasi-static ideal gas cycles, and the necessary conditions for refrigeration cycles are clarified. Three logically self-consistent criteria can be used to determine if a counterclockwise cycle is a refrigerator. The most fundamental test compares the counterclockwise cycle with a correctly determined corresponding Carnot cycle. Other criteria we employ include a widely accepted description of the functional behavior of refrigerators, and a corollary to the second law that limits a refrigerator's coefficient of performance.
This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allow able without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manu script in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. ACKNOWLEDGMENTS The author wishes to thank Professor C. T. Tomizuka for his guidance and encouragement throughout this research project, Mr. Rodney C. Lowell for his contributions in setting up the high pressure laboratory and for operating the high pressure apparatus, Dr. E. Daniel Albrecht for his contributions in designing much of the apparatus used in the course of this research, and Mr. Donald E. McDonald for his assistance with the electrical and electronic apparatus. The early stages of this research project were sponsored by the U. S. Air Force Office of Scientific Research through Contract No. AF 49(638)-790, and the later stages by the U. S. Atomic Energy Commission through Contract No. AT(ll-l)-1041. The support of these agencies is gratefully acknowl edged. lii
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