first law of thermodynamics(redirected from 1st Law)
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first law of thermodynamics[′fərst ‚lȯ əv ‚thər·mō·dī′nam·iks]
The law that heat is a form of energy, and the total amount of energy of all kinds in an isolated system is constant; it is an application of the principle of conservation of energy.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.