The First Law of Thermodynamics
The change in internal energy 
U
of a system is equal to the heat that flows into the system Q minus the work
W done by the system on its surroundings;
U
= Q - W
this is known as the First Law of Thermodynamics.
The First Law of Thermodynamics is a restatement of the Work-Energy Theorem and the ideas of Conservation of Energy.
Example:
Example:
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