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Definition of First law of thermodynamics
1. Noun. The fundamental principle of physics that the total energy of an isolated system is constant despite internal changes.
Generic synonyms: Law Of Thermodynamics, Conservation
Medical Definition of First law of thermodynamics
1. This law, derived from the principle of conservation of energy, is expressed as E = Q - W, where E is the internal change in energy, Q is the heat the environment transfers into the system, and W is the work the system does. In other words, it means that: The internal energy in a system isolated from other systems remains constant The change in the internal energy of a system that is not isolated is equal to the energy that crosses its boundariesinto or out of other systemsIt can be further extrapolated to mean that despite all the processesgoing on in the universe, the total energy contained in the universeremains constant. (09 Oct 1997)