Heat

Type of energy transfer "Heating" redirects here; not to be confused with Home heating or Heat wave. This article is about a type of energy transfer. For the film, see Heat (1995 film). For other uses, see Heat (disambiguation). HeatA glowing-hot metal bar showing incandescence, the emission of light due to its temperature, is often recognized as a source of heat.Common symbols Q {\displaystyle Q} SI unitjouleOther unitsBritish thermal unit, calorieIn SI base unitskg⋅m2⋅s−2Dimension L 2 M T − 2 {\displaystyle {\mathsf {L}}^{2}{\mathsf {M}}{\mathsf {T}}^{-2}} ThermodynamicsThe classical Carnot heat engine Branches Classical Statistical Chemical Quantum thermodynamics Equilibrium / Non-equilibrium Laws Zeroth First Second Third Systems Closed system Open system Isolated system State Equation of state Ideal gas Real gas State of matter Phase (matter) Equilibrium Control volume Instruments Processes Isobaric Isochoric Isothermal Adiabatic Isentropic Isenthalpic Quasistatic Polytropic Free expansion Reversibility Irreversibility Endoreversibility Cycles Heat engines Heat pumps Thermal efficiency System propertiesNote: Conjugate variables in italics Property diagrams Intensive an