Explore: Internal Energy

The internal energy of a thermodynamic system is the energy of the system as a state function, measured as the quantity of energy necessary to bring the

"thermal energy" is often used ambiguously in physics and engineering. It can denote several different physical concepts, including: Internal energy: The

with the equipartition theorem, so all available internal degrees of freedom have the same average energy as do their three external degrees of freedom.

the radiant energy carried by electromagnetic radiation, the internal energy contained within a thermodynamic system, and rest energy associated with

matter excluded), the heat involved in a process is the difference in internal energy between the final and initial states of a system, after subtracting

free energy is expressed as G ( p , T ) = U + p V − T S = H − T S {\displaystyle G(p,T)=U+pV-TS=H-TS} where: U {\textstyle U} is the internal energy of

system's internal energy be consumed, so that the amount of internal energy lost by that work must be resupplied as heat by an external energy source or

gravitational potential (higher internal energy thus higher potential for work) to a lower gravitational potential (lower internal energy). In the same way, as

{\displaystyle \Delta {U_{f}^{\circ }}_{\mathrm {reactants} }} , the internal energy of formation of the reactant molecules, and Δ U f ∘ p r o d u c t s

may generate thermal energy, causing the material's temperature to rise. Thermal energy in solids is often carried by internal elastic waves, called