Get our free book (in Spanish or English) on rainwater now - To Catch the Rain.

# User:RichardF/Outline of energy

In physics, energy (from the Greekenergeia, "activity, operation", – energos, "active, working"[1]) is a scalar physical quantity that describes the amount of work that can be performed by a force. Energy is an attribute of objects and systems that is subject to a conservation law. Several different forms of energy exist to explain all known natural phenomena. These forms include (but are not limited to) kinetic, potential, thermal, gravitational, sound, light, elastic, and electromagnetic energy. The forms of energy are often named after a related force.

Any form of energy can be transformed into another form, but the total energy always remains the same. This principle, the conservation of energy, was first postulated in the early 19th century, and applies to any isolated system. According to Noether's theorem, the conservation of energy is a consequence of the fact that the laws of physics do not change over time.[2]

Although the total energy of a system does not change with time, its value may depend on the frame of reference. For example, a seated passenger in a moving airplane has zero kinetic energy relative to the airplane, but non-zero kinetic energy relative to the Earth.

The following outline is provided as an overview of and topical guide to energy:

## Essence of energy

Main article: Energy

## Energy units (terms)

• Barrel of oil equivalent
• British thermal unit
• Calorie
• Current solar income – the amount of solar energy that falls as sunlight
• Electronvolt – (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt
• Planck energy, 1.22 × 1019 GeV (billion electron volts)
• Enthalpy
• Erg – (symbol "erg") unit of energy and mechanical work in the centimetre-gram-second (CGS) system of units
• EU energy label
• Fill factor – defined as the ratio of the maximum power (Vmp x Jmp) divided by the short-circuit current (Isc) and open-circuit voltage (Voc) in light current density – voltage (J-V) characteristics of solar cells.
• Foot-pound – (symbol ft·lbf or ft·lbf) is an Imperial and U.S. customary unit of mechanical work, or energy, although in scientific fields one commonly uses the equivalent metric unit of the joule (J). There are approximately 1.356 J/(ft·lbf).
• Gigaton – Metric Unit of mass, equal to 1,000,000,000 (1 billion) metric tons, 1,000,000,000,000 (1 trillion) kilograms
• Any of various units of energy, such as gigatons of TNT equivalent, gigatons of coal equivalent, gigatons petroleum equivalent.
• Gray (unit) – (symbol: Gy), is the SI unit of energy for the absorbed dose of radiation. One gray is the absorption of one joule of radiation energy by one kilogram of matter. One gray equals 100 rad, an older unit.
• Heat
• Joule – (symbol J, also called newton meter, watt second, or coulomb volt)
• Kilowatt-hour – (symbol: kW·h) corresponds to one kilowatt (kW) of power being used over a period of one hour.
• Mass-energy equivalence – where mass has an energy equivalence, and energy has a mass equivalence
• Megawatt
• Net energy gain
• Power factor – of an AC electric power system is defined as the ratio of the real power to the apparent power.
• Therm – (symbol thm) a non-SI unit of heat energy. It is approximately the heat equivalent of burning 100 cubic feet of natural gas. In the US gas industry it is defined as exactly 100,000 BTU59°F or 105.4804 megajoules.
• Ton of oil equivalent
• TPE – Ton Petroleum Equivalent, 45.217 GJ, see ton of oil equivalent

## History of energy

Main article: History of energy

## Energy infrastructure

See especially Category:Electric power and Category:Fuels for a large number of conventional energy related topics.

## Physics of energy

### Allegorical, esoteric, and pseudoscientific

• Energy (esotericism), invoked by spiritualists for alternative modes of healing the human body as well as a spirit that permeates all of reality.
• Orgone, Wilhelm Reich discovered this energy and tried to use it to cure various physical ailments and control the weather.
• Qi a concept from Oriental medicine that is sometimes translated as "energy" in the West.
• Vitalism, often referred to as "energy"
• Cold fusion, nuclear fusion at conditions close to room temperature.
• Bubble fusion, also known as Sonofusion, energy from acoustic collapse of bubbles.
• Water-fuelled car, powering a car using water as fuel.

## Energy economics

### Industry associations

• OPEC – Organization of Petroleum-exporting Countries
• IEA – International Energy Agency
• CAPP – Canadian Association of Petroleum Producers
• World LP Gas Association – WLPGA