In physics, energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object.[note 1] Energy is a conserved quantity; the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The SI unit of energy is the joule, which is the energy transferred to an object by the work of moving it a distance of 1 metre against a force of 1 newton.
Common forms of energy include the kinetic energy of a moving object, the potential energy stored by an object's position in a force field (gravitational, electric or magnetic), the elastic energy stored by stretching solid objects, the chemical energy released when a fuel burns, the radiant energy carried by light, and the thermal energy due to an object's temperature.
Mass and energy are closely related. 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. For example, after heating an object, its increase in energy could be measured as a small increase in mass, with a sensitive enough scale.
Living organisms require energy to stay alive, such as the energy humans get from food. Human civilization requires energy to function, which it gets from energy resources such as fossil fuels, nuclear fuel, or renewable energy. The processes of Earth's climate and ecosystem are driven by the radiant energy Earth receives from the sun and the geothermal energy contained within the earth.
Explanation:
Some forms of energy (that an object or system can have as a measurable property)
Type of energyDescription
Mechanicalthe sum of macroscopic translational and rotational kinetic and potential energies
Electricpotential energy due to or stored in electric fields
Magneticpotential energy due to or stored in magnetic fields
Gravitationalpotential energy due to or stored in gravitational fields
Chemicalpotential energy due to chemical bonds
Ionizationpotential energy that binds an electron to its atom or molecule
Nuclearpotential energy that binds nucleons to form the atomic nucleus (and nuclear reactions)
Chromodynamicpotential energy that binds quarks to form hadrons
Elasticpotential energy due to the deformation of a material (or its container) exhibiting a restorative force
Mechanical wavekinetic and potential energy in an elastic material due to a propagated deformational wave
Sound wavekinetic and potential energy in a fluid due to a sound propagated wave (a particular form of mechanical wave)
Radiantpotential energy stored in the fields of propagated by electromagnetic radiation, including light
Restpotential energy due to an object's rest mass
Thermalkinetic energy of the microscopic motion of particles, a form of disordered equivalent of mechanical energy
Main articles: History of energy and timeline of thermodynamics, statistical mechanics, and random processes
