| a function of thermodynamic variables, as temperature, that represents the internal state of a system that is due to the energies of the molecular constituents of the system. The change in internal energy during a process is equal to the net heat entering the system minus the net work done by the system. Symbol: U |
| internal energy n. Symbol U The total kinetic and potential energy associated with the motions and relative positions of the molecules of an object, excluding the kinetic or potential energy of the object as a whole. An increase in internal energy results in a rise in temperature or a change in phase. |
internal energy
in thermodynamics, the property or state function that defines the energy of a substance in the absence of effects due to capillarity and external electric, magnetic, and other fields. Like any other state function, the value of the energy depends upon the state of the substance and not upon the nature of the processes by which it attained that state. In accordance with the first law of thermodynamics, when a system undergoes a change of state as a result of a process in which only work is involved, the work is equal to the change in internal energy. The law also implies that if both heat and work are involved in the change of state of a system, then the change in internal energy is equal to the heat supplied to the system minus the work done by the system
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