The watt (symbol: W) is the SI derived unit of power, equal to one joule of energy per second. SI derived units are part of the SI system of measurement units and are derived from the seven SI base units They are derived from SI basic units/defined In Physics, power (symbol P) is the rate at which work is performed or energy is transmitted or the amount of energy required or expended for The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity The second ( SI symbol s) sometimes abbreviated sec, is the name of a unit of Time, and is the International System of Units It measures a rate of energy use or production.

A human climbing a flight of stairs is doing work at a rate of about 200 watts. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus A typical automobile engine produces mechanical energy at a rate of 25,000 watts (approximately 33. 5 horsepower) while cruising. A typical household incandescent light bulb uses electrical energy at a rate of 25 to 100 watts, while compact fluorescent lights typically consume 5 to 30 watts. The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric Light that works by Incandescence, (a general

Definition

.

In electrical terms, it follows that:

Or, in terms of volts and amperes:

That is, if 1 volt of potential difference is applied to a resistive load, and a current of 1 ampere flows, then 1 watt of power is dissipated. The volt (symbol V) is the SI derived unit of electric Potential difference or Electromotive force. In Physics, the potential difference or pd between two points is the difference of the points' Scalar potential, equivalent to the line integral The ampere, in practice often shortened to amp, (symbol A is a unit of Electric current, or amount of Electric charge per second ^[1] More simply stated: watts is equal to amps times volts. The ampere, in practice often shortened to amp, (symbol A is a unit of Electric current, or amount of Electric charge per second The volt (symbol V) is the SI derived unit of electric Potential difference or Electromotive force.

Note that the electrical definitions are true instantaneously, and for DC voltage and current. The Volt-ampere article explains the consequences when the RMS voltage and current are measured separately. A volt-ampere in electrical terms means the amount of Apparent power in an Alternating current circuit equal to a current of one Ampere at an In Mathematics, the root mean square (abbreviated RMS or rms) also known as the quadratic mean, is a statistical measure of the

Origin and adoption as an SI unit

The watt is named after James Watt for his contributions to the development of the steam engine, and was adopted by the Second Congress of the British Association for the Advancement of Science in 1889 and by the 11th General Conference on Weights and Measures in 1960 as the unit of power incorporated in the International System of Units (or "SI"). James Watt ( 19 January 1736 &ndash 25 August 1819 Boulton proved to be an excellent businessman and both men eventually made fortunes A steam engine is a Heat engine that performs Mechanical work using Steam as its Working fluid. The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures ( CGPM, never GCWM

Derived and qualified units for power distribution

Kilowatt

The kilowatt (symbol: kW), equal to one thousand watts, is typically used to state the power output of engines and the power consumption of tools and machines. An engine is a mechanical device that produces some form of output from a given input A kilowatt is roughly equivalent to 1. 34 horsepower. An electric heater with one heating-element might use 1 kilowatt.

Megawatt

The megawatt (symbol: MW) is equal to one million (10⁶) watts. The word million In standard English, the -lli- in million is pronounced with an l-sound followed by a

Many things can sustain the transfer or consumption of energy on this scale; some of these events or entities include: lightning strikes, large electric motors, naval craft (such as aircraft carriers and submarines), engineering hardware, and some scientific research equipment (such as the supercollider and large lasers). Lightning is an atmospheric discharge of Electricity, which typically occurs during Thunderstorms and sometimes during volcanic eruptions or An aircraft carrier is a Warship designed with A submarine is a Watercraft that can operate independently below water as distinct from a Submersible that has only limited underwater capability SuperCollider is an environment and Programming language originally released in 1996 by James McCartney for Real time Audio synthesis and Algorithmic A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. A large residential or retail building may consume several megawatts in electric power and heating energy.

The productive capacity of electrical generators operated by utility companies is often measured in MW. In Electricity generation, an electrical generator is a device that converts Mechanical energy to Electrical energy, generally using Electromagnetic A public utility (usually just utility) is an organization that maintains the Infrastructure for a public service (often also providing a service using Modern high-powered diesel-electric railroad locomotives typically have a peak power output of 3 to 5 MW, whereas U. A number of vehicles use a diesel-electric Powertrain for providing locomotion. A locomotive is a railway Vehicle that provides the motive power for a Train. S. nuclear power plants have net summer capacities between about 500 and 1300 MW. Nuclear power is any Nuclear technology designed to extract usable Energy from atomic nuclei via controlled Nuclear reactions ^[2]

According to the Oxford English Dictionary, the earliest citing for "megawatt" is a reference in the 1900 Webster's International Dictionary of English Language. The Oxford English Dictionary ( OED) published by the Oxford University Press (OUP is a comprehensive Dictionary of the English Webster's Dictionary is the name given to a common type of English language dictionary in the United States. The OED also says "megawatt" appeared in a 28 November 1847, article in Science (506:2). For the town in Argentina, see 28 de Noviembre. Events Year 1847 ( MDCCCXLVII) was a Common year starting on Friday (link will display the full calendar of the Gregorian Calendar (or a Common Science is the Academic journal of the American Association for the Advancement of Science and is considered one of the world's most prestigious Scientific

Gigawatt

The gigawatt (symbol: GW) is equal to one billion (10⁹) watts. This unit is sometimes used with large power plants or power grids.

Terawatt

The terawatt (symbol: TW) is equal to one trillion (10¹²) watts. The average energy usage of the earth (about 15 TW) is commonly measured in these units. The most powerful lasers from the mid 1960s to the mid 1990s produced power in terawatts, but only for nanoseconds. A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. The 1960s decade refers to the years from the beginning of 1960 to the end of 1969 The 1990s collectively refers to the years between and including 1990 and 1999 A nanosecond ( ns) is one billionth of a second See also times of other orders of magnitude.

Electrical and thermal

Megawatt electrical (abbreviation: MW_e or MWe^[3]) is a term that refers to electric power, while megawatt thermal (abbreviations: MW_t, MW_th, MWt, or MWth) refers to thermal power produced. Electric power is defined as the rate at which Electrical energy is transferred by an Electric circuit. Though 'megawatt electrical' and 'megawatt thermal' are not SI units,^[4] alternative SI prefixes are sometimes used, for example gigawatt electrical (GW_e). An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol to form a Decimal multiple or The International Bureau of Weights and Measures states that unit symbols should not use subscripts to provide additional information about the quantity being measured, and regards these symbols as incorrect. The International Bureau of Weights and Measures ( Bureau international des poids et mesures, in French) is an international Standards organization, one ^[5]

These terms are used by engineers to disambiguate the electric output of a thermal power station versus the (larger) thermal output. A power station (also referred to as generating station, power plant or powerhouse) is an industrial facility for the generation of For example, the Embalse nuclear power plant in Argentina uses a fission reactor to generate 2109 MW_t of heat, which creates steam to drive a turbine, which generates 648 MW_e of electricity. The Embalse nuclear power plant (Central Nuclear Embalse is one of the two operational Nuclear power plants in Argentina. This article is a subarticle of Nuclear power. A nuclear reactor is a device in which Nuclear chain reactions are initiated controlled The difference is heat lost to the surroundings.

Confusion of watts and watt-hours

Power and energy are frequently confused in the general media. In Physics, power (symbol P) is the rate at which work is performed or energy is transmitted or the amount of energy required or expended for In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός A watt is one 1 joule of energy per second. So watts multiplied by a period of time equals energy. For example, if a 100 watt light bulb is turned on for one hour, then an amount of energy is used corresponding to 100 watts of power being generated for a time period of one hour, i. e. 100 watts times one hour, i. e. 0. 1 kilowatt-hour.

Since a joule as a quantity of energy does not have a readily imagined size to the layperson, the non-SI unit watt-hour, often in its multiples such the kilowatt-hour or higher prefixes, is frequently used as a unit of energy, especially by energy-supply companies (electricity and natural gas suppliers), which often quote charges by the kilowatt-hour. A kilowatt-hour is the amount of energy equivalent to a power of 1 kilowatt running for 1 hour:

(1 kW·h)(1000 W/kW)(3600 s/h) = 3,600,000 W·s = 3,600,000 J = 3. 6 MJ. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity

See also

References

External links

• Nelson, Robert A. , "The International System of Units Its History and Use in Science and Industry". Via Satellite, February 2000.