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Chapter 10 - ENERGY: CONSERVATION AND CONVERSION

Published online by Cambridge University Press:  05 August 2013

Steven C. Frautschi ,
Richard P. Olenick ,
Tom M. Apostol  and
David L. Goodstein
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Summary

… You see, therefore, that living force [energy] may be converted into heat, and that heat may be converted into living force, or its equivalent attraction through space. All three, therefore – namely, heat, living force, and attraction through space (to which I might also add light, were it consistent with the scope of the present lecture) – are mutually convertible into one another. In these conversions nothing is ever lost. The same quantity of heat will always be converted into the same quantity of living force. We can therefore express the equivalency in definite language applicable at all times and under all circumstances.

James Prescott Joule, “On Matter, Living Force, and Heat” (1847)

TOWARD AN IDEA OF ENERGY

The law of conservation of energy is one of the most fundamental laws of physics. No matter what you do, energy is always conserved. So why do people tell us to conserve energy? Evidentally the phrase “conserve energy” has one meaning to a scientist and quite a different meaning to other people, for example, to the president of a utility company or to a politician. What then, exactly, is energy?

The notion of energy is one of the few elements of mechanics not handed down to us from Isaac Newton. The idea was not clearly grasped until the middle of the nineteenth century. Nevertheless, we can find its germ even earlier than Newton.

Type
Chapter
Information
The Mechanical Universe
Mechanics and Heat, Advanced Edition
 , pp. 219 - 262
Publisher: Cambridge University Press
Print publication year: 1986

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