Definition - What does Internal Energy mean?
Internal Energy is the energy contained in a system or the energy needed to create a system. This energy does not account for kinetic energy of motion and the potential energy of the system because of external force fields. It is closely related to the temperature of the system. Internal energy accounts for any gain or loss of energy in the system.
Petropedia explains Internal Energy
The internal energy of any system has two components:
- System’s Kinetic Energy
- System’s Potential Energy
Kinetic energy of a system includes all the energies required to make the system come in motion. This includes either forward or backward motion, vibrations, translation and rotations. The potential energy of the system is associated with the static constituents of matter static electric energy of atoms within molecules or crystals, and the energy from chemical bonds. Thus the total internal energy (U) of a system can be expressed as: