Energy: Difference between revisions - Wikipedia

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{{Thermodynamics}}

In [[physics]], '''energy''' ({{etymology|grc|''{{wiktgrc|ἐνέργεια}}'' ({{grc-transl|ἐνέργεια}})|activity}}) is the [[physical quantity|quantitative]] [[physical property|property]] that is [[#Energy transfer|transferred]] to a [[physical body|body]] or to a [[physical system]], recognizable in the performance of [[Work (thermodynamics)|work]] and in the form of [[heat]] and [[light]]. Energy is a [[Conservation law|conserved quantity]]—the law of [[conservation of energy]] states that energy can be [[Energy transformation|converted]] in form, but not created or destroyed; [[matter]] and energy may also be converted to one another. The unit of [[measurement]] for energy in the [[International System of Units]] (SI) is the [[joule]] (J).

Common forms of energy include the [[kinetic energy]] of a moving object, the [[potential energy]] stored by an object (for instance due to its position in a [[Classical field theory|field]]), the [[elastic energy]] stored in a solid object, [[chemical energy]] associated with [[chemical reaction]]s, the [[radiant energy]] carried by [[electromagnetic radiation]], and the [[internal energy]] contained within a [[thermodynamic system]]. All living [[organism]]s constantly take in and release energy.

Due to [[mass–energy equivalence]], any object that has [[mass]] when stationary (called [[rest mass]]) also has an equivalent amount of energy whose form is called [[rest energy]], and any additional energy (of any form) acquired by the object above that rest energy will increase the object's total mass just as it increases its total energy.

Human civilization requires energy to function, which it gets from [[energy resource]]s such as [[fossil fuel]]s, [[nuclear fuel]], or [[renewable energy]]. The Earth's [[climate]] and [[ecosystem]]s processes are driven by the energy the planet receives from the Sun (although a small amount is also contributed by [[geothermal energy]]).