View source for First law of thermodynamics

[[Category:Done 2018-06-01]]  
<onlyinclude>The '''first law of thermodynamics''' states that the change in [[internal energy]] of a system (<math>\Delta U</math>) is equal to the [[work]] done by or to the [[system]] (<math>W</math>) and the [[heat]] that flows in or out of it (<math>Q</math>).</onlyinclude>

The equation for this relationship is:
<math>\Delta U = W + Q</math><ref name= knight>R. Knight, Physics for scientists and engineers. Boston, Mass.: Addison-Wesley, 2012, p. 478.</ref>

This means that if [[energy]] is input to a system by doing work <math>W</math> on it, then it will get hotter. If the system is to stay the same [[temperature]], then you must remove heat from the system - <math>Q</math>.

The first law of [[thermodynamics]] is a generalization of the [[law of conservation of energy]], which states that energy can neither be created nor destroyed.<ref name= knight/>

This is a particularly important law when discussing [[heat engine]]s (like car engines), because it helps to understand that heat must go somewhere—the basis for [[cogeneration]]. As an [[engine]] creates [[heat]], if the heat is not vented, the engine will become hotter and hotter, which will eventually lead to melting. Therefore, because it is impossible to achieve 100% [[efficiency]] (see [[carnot efficiency]]), heat must be vented. This can either be treated as [[waste heat]], or used for [[cogeneration]], which is applying the waste heat to another cause, like heating a car, or heating houses.

To learn more about the first law of thermodynamics, please check out [http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/firlaw.html#c1 hyperphysics].

==For Further Reading==
*[[Law of conservation of energy]]
*[[Internal energy]]
*[[Work]]
*[[Heat]]
*[[Carnot efficiency]]
*Or explore a [[Special:Random| random page]]

==References==
{{reflist}}

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