First Law of Thermodynamics

[noun]

One of three Laws of Thermodynamics, or laws relating to heat power. The First Law explores the conservation of energy. Specifically, this law explains that energy cannot be created or destroyed, only transformed from one form to another. It also states that the energy within a closed system is fixed – it cannot increase or decrease. The First Law is often expressed as an equation: ∆U = Q - W, or the change in internal energy (∆U) equals the heat added to the system (Q) minus the work done by the system (W). See also the Second Law of Thermodynamics and the Third Law of Thermodynamics.