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Capacity for doing work. Energy exists in various formsincluding kinetic, potential, thermal, chemical, electrical (seeelectricity), and nuclearand can be converted from one form to another. For example, fuel-burning heat engines convert chemical energy to thermal energy; batteries convert chemical energy to electrical energy. Though energy may be converted from one form to another, it may not be created or destroyed; that is, total energy in a closed system remains constant. All forms of energy are associated with motion. A rolling ball has kinetic energy, for instance, whereas a ball lifted above the ground has potential energy, as it has the potential to move if released. Heat and work involve the transfer of energy; heat transferred may become thermal energy. See alsoactivation energy, binding energy, ionization energy, mechanical energy, solar energy, zero-point energy.
This entry comes from Encyclopædia Britannica Concise. For the full entry on energy, visit Britannica.com.