# Word Net

watt### Noun

1 a unit of power equal to 1 joule per second;
the power dissipated by a current of 1 ampere flowing across a
resistance of 1 ohm [syn: W]

2 Scottish engineer and inventor whose
improvements in the steam engine led to its wide use in industry
(1736-1819) [syn: James
Watt]

see Watt

# English

## Etymology

Named after the Scottish engineer James Watt.## Homophones

- wat
- what (in accents with the wine-whine merger)
- wot

## Noun

- In the International System of Units, the derived unit of power; the power of a system in which one joule of energy is transferred per second. Symbol: W

### Translations

- Bulgarian: ват
- Chinese: 瓦特 (wate)
- Finnish: watti
- French: watt
- German: Watt
- Italian: watt (p: watt)
- Japanese: ワット
- Polish: wat
- Russian: ватт
- Spanish: vatio, watt
- Swedish: watt

## See also

# French

## Noun

watt- watt

# Italian

## Noun

watt- watt
- watts

# Spanish

## Noun

- watt

# Swedish

## Noun

- watt

The watt (symbol: W) is the SI derived
unit of power,
equal to one joule of
energy per second. 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. 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.

# Definition

1~\rm = 1~\dfrac = 1~\dfrac = 1~\dfrac \, .In electrical terms, it follows that:

- 1~\rm = \dfrac \times 1~\rm

Or, in terms of volts and amperes: 1~\rm = 1~\rm
\times 1~\rm \,

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. More simply stated: watts is equal to
amps times volts.

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.

# 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").# 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. 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. 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). 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. Modern high-powered diesel-electric
railroad locomotives
typically have a peak power output of 3 to 5 MW, whereas U.S.
nuclear
power plants have net summer capacities between about 500 and
1300 MW.

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 OED also says
"megawatt" appeared in a 28 November,
1847, article
in Science
(506:2).

## 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.## Electrical and thermal

Megawatt electrical (abbreviation: MWe or MWe) is a term that refers to electric power, while megawatt thermal (abbreviations: MWt, MWth, MWt, or MWth) refers to thermal power produced. Though 'megawatt electrical' and 'megawatt thermal' are not SI units, alternative SI prefixes are sometimes used, for example gigawatt electrical (GWe). 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.These terms are used by engineers to disambiguate
the electric output of a
thermal power station versus the (larger) thermal output. For
example, the
Embalse nuclear power plant in Argentina uses a fission
reactor to generate 2109 MWt of heat, which creates steam to
drive a turbine, which generates 648 MWe of electricity. The
difference is heat lost to the surroundings.

# Confusion of watts and watt-hours

Power and energy are frequently confused in the general media. 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.

# See also

portal Energy# References

# External links

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

watt in Arabic: واط

watt in Asturian: Vatiu

watt in Bengali: ওয়াট (একক)

watt in Min Nan: Oá

watt in Belarusian: Ват

watt in Belarusian (Tarashkevitsa): Ват

watt in Bosnian: Vat

watt in Breton: Watt

watt in Bulgarian: Ват

watt in Catalan: Watt

watt in Czech: Watt

watt in Danish: Watt

watt in German: Watt (Einheit)

watt in Estonian: Vatt (ühik)

watt in Modern Greek (1453-): Βατ (μονάδα
μέτρησης)

watt in Spanish: Vatio

watt in Esperanto: Vato (unuo)

watt in Basque: Watt

watt in French: Watt

watt in Friulian: Wat

watt in Gan Chinese: 瓦

watt in Galician: Watt

watt in Korean: 와트

watt in Croatian: Vat

watt in Indonesian: Watt

watt in Icelandic: Vatt

watt in Italian: Watt

watt in Hebrew: ואט

watt in Kurdish: Wat

watt in Latin: Wattium

watt in Latvian: Vats

watt in Lithuanian: Vatas

watt in Hungarian: Watt (mértékegység)

watt in Macedonian: Ват

watt in Malay (macrolanguage): Watt

watt in Dutch: Watt

watt in Japanese: ワット

watt in Norwegian: Watt (effekt)

watt in Norwegian Nynorsk: Watt

watt in Polish: Wat

watt in Portuguese: Watt

watt in Kölsch: Watt (Mohß)

watt in Romanian: Watt

watt in Russian: Ватт

watt in Scots: Watt

watt in Simple English: Watt

watt in Slovak: Watt (jednotka)

watt in Slovenian: Vat

watt in Serbian: Ват

watt in Serbo-Croatian: Watt

watt in Finnish: Watti

watt in Swedish: Watt

watt in Thai: วัตต์

watt in Vietnamese: Watt

watt in Turkish: Watt

watt in Ukrainian: Ват

watt in Urdu: واٹ

watt in Contenese: 瓦 (單位)

watt in Chinese: 瓦特