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The dimension of power is energy divided by time. In the International System of Units (SI), the unit of power is the watt (W), which is equal to one joule per second. Other common and traditional measures are horsepower (hp), comparing to the power of a horse; one mechanical horsepower equals about 745.7 watts.
The energy that a physical body possesses due to its motion, defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. The body continues to maintain this kinetic energy unless its velocity changes. Contrast potential energy. Kirchhoff's circuit laws. Also called Kirchhoff's rules or simply Kirchhoff's laws.
Energy Journal 27.1 (2006). Gales, Ben, et al. "North versus South: Energy transition and energy intensity in Europe over 200 years". European Review of Economic History 11.2 (2007): 219-253. Nye, David E. Consuming power: A social history of American energies (MIT Press, 1999) Pratt, Joseph A. Exxon: Transforming Energy, 1973-2005 (2013) 600pp
However energy can also be expressed in many other units not part of the SI, such as ergs, calories, British thermal units, kilowatt-hours and kilocalories, which require a conversion factor when expressed in SI units. The SI unit of power, defined as energy per unit of time, is the watt, which is a joule per second. Thus, one joule is one watt ...
In order of the typical magnitude of the energy stored, examples of reactions are: nuclear, chemical (including electrochemical), electrical, pressure, material deformation or in electromagnetic fields. Nuclear reactions take place in stars and nuclear power plants, both of which derive energy from the binding energy of nuclei.
An energy transition is a broad shift in technologies and behaviours that are needed to replace one source of energy with another. [14]: 202–203 A prime example is the change from a pre-industrial system relying on traditional biomass, wind, water and muscle power to an industrial system characterized by pervasive mechanization, steam power and the use of coal.
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Solar power, wind power, hydroelectricity, geothermal energy, and biomass are widely agreed to be the main types of renewable energy. [21] Renewable energy often displaces conventional fuels in four areas: electricity generation , hot water / space heating , transportation , and rural (off-grid) energy services.