30-544: Armstrong Power Station was a 356 megawatt ( MW ), coal power plant in Washington Township , Armstrong County along the Allegheny River across from Mahoning Creek and Templeton, Pennsylvania , about 10 miles (16 km) north of Kittanning, Pennsylvania . The plant operated from 1958 to 2012. Armstrong's two units went in service in 1958 and 1959. The chimney of Armstrong Power Station, which
60-558: A light bulb with a power rating of 100 W is turned on for one hour, the energy used is 100 watt hours (W·h), 0.1 kilowatt hour, or 360 kJ . This same amount of energy would light a 40-watt bulb for 2.5 hours, or a 50-watt bulb for 2 hours. Power stations are rated using units of power, typically megawatts or gigawatts (for example, the Three Gorges Dam in China is rated at approximately 22 gigawatts). This reflects
90-489: A relative uncertainty of approximately a few parts in 10 , and involved realisations of the watt, the ohm and the volt. The 2019 revision of the SI defined the ampere by taking the fixed numerical value of the elementary charge e to be 1.602 176 634 × 10 when expressed in the unit C, which is equal to A⋅s, where the second is defined in terms of ∆ ν Cs , the unperturbed ground state hyperfine transition frequency of
120-449: A silver nitrate solution. Later, more accurate measurements revealed that this current is 0.999 85 A . Since power is defined as the product of current and voltage, the ampere can alternatively be expressed in terms of the other units using the relationship I = P / V , and thus 1 A = 1 W/V. Current can be measured by a multimeter , a device that can measure electrical voltage, current, and resistance. Until 2019,
150-515: A period of one year: equivalent to approximately 114 megawatts of constant power output. The watt-second is a unit of energy, equal to the joule . One kilowatt hour is 3,600,000 watt seconds. While a watt per hour is a unit of rate of change of power with time, it is not correct to refer to a watt (or watt-hour) as a watt per hour. Ampere The ampere ( / ˈ æ m p ɛər / AM -pair , US : / ˈ æ m p ɪər / AM -peer ; symbol: A ), often shortened to amp ,
180-541: A turbine, which generates 648 MW e (i.e. electricity). Other SI prefixes are sometimes used, for example gigawatt electrical (GW e ). The International Bureau of Weights and Measures , which maintains the SI-standard, states that further information about a quantity should not be attached to the unit symbol but instead to the quantity symbol (e.g., P th = 270 W rather than P = 270 W th ) and so these unit symbols are non-SI. In compliance with SI,
210-495: A unit of time, namely 1 J/s. In this new definition, 1 absolute watt = 1.00019 international watts. Texts written before 1948 are likely to be using the international watt, which implies caution when comparing numerical values from this period with the post-1948 watt. In 1960, the 11th General Conference on Weights and Measures adopted the absolute watt into the International System of Units (SI) as
240-862: Is 1.2 A") and the charge accumulated (or passed through a circuit) over a period of time is expressed in coulombs (as in "the battery charge is 30 000 C "). The relation of the ampere (C/s) to the coulomb is the same as that of the watt (J/s) to the joule . The international system of units (SI) is based on seven SI base units the second , metre, kilogram , kelvin , ampere, mole , and candela representing seven fundamental types of physical quantity, or "dimensions" , ( time , length , mass , temperature , electric current, amount of substance , and luminous intensity respectively) with all other SI units being defined using these. These SI derived units can either be given special names e.g. watt, volt, lux , etc. or defined in terms of others, e.g. metre per second . The units with special names derived from
270-733: Is named after the Scottish inventor James Watt . The unit name was proposed by C. William Siemens in August 1882 in his President's Address to the Fifty-Second Congress of the British Association for the Advancement of Science . Noting that units in the practical system of units were named after leading physicists, Siemens proposed that watt might be an appropriate name for a unit of power. Siemens defined
300-523: Is the rate at which electrical work is performed when a current of one ampere (A) flows across an electrical potential difference of one volt (V), meaning the watt is equivalent to the volt-ampere (the latter unit, however, is used for a different quantity from the real power of an electrical circuit). 1 W = 1 V ⋅ A . {\displaystyle \mathrm {1~W=1~V{\cdot }A} .} Two additional unit conversions for watt can be found using
330-412: Is the unit of electric current in the International System of Units (SI). One ampere is equal to 1 coulomb (C) moving past a point per second. It is named after French mathematician and physicist André-Marie Ampère (1775–1836), considered the father of electromagnetism along with Danish physicist Hans Christian Ørsted . As of the 2019 revision of the SI , the ampere is defined by fixing
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#1732798244664360-406: Is used in the formal definition of the ampere. The SI unit of charge, the coulomb , was then defined as "the quantity of electricity carried in 1 second by a current of 1 ampere". Conversely, a current of one ampere is one coulomb of charge going past a given point per second: In general, charge Q was determined by steady current I flowing for a time t as Q = It . This definition of
390-446: The caesium -133 atom. The SI unit of charge, the coulomb , "is the quantity of electricity carried in 1 second by a current of 1 ampere". Conversely, a current of one ampere is one coulomb of charge going past a given point per second: In general, charge Q is determined by steady current I flowing for a time t as Q = I t . Constant, instantaneous and average current are expressed in amperes (as in "the charging current
420-527: The elementary charge e to be exactly 1.602 176 634 × 10 C , which means an ampere is an electric current equivalent to 10 elementary charges moving every 1.602 176 634 seconds or 6.241 509 074 × 10 elementary charges moving in a second. Prior to the redefinition the ampere was defined as the current passing through two parallel wires 1 metre apart that produces a magnetic force of 2 × 10 newtons per metre. The earlier CGS system has two units of current, one structured similarly to
450-478: The SI defined the ampere as follows: The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed one metre apart in vacuum, would produce between these conductors a force equal to 2 × 10 newtons per metre of length. Ampère's force law states that there is an attractive or repulsive force between two parallel wires carrying an electric current. This force
480-508: The SI's and the other using Coulomb's law as a fundamental relationship, with the CGS unit of charge defined by measuring the force between two charged metal plates. The CGS unit of current is then defined as one unit of charge per second. The ampere is named for French physicist and mathematician André-Marie Ampère (1775–1836), who studied electromagnetism and laid the foundation of electrodynamics . In recognition of Ampère's contributions to
510-470: The above equation and Ohm's law . 1 W = 1 V 2 / Ω = 1 A 2 ⋅ Ω , {\displaystyle \mathrm {1~W=1~V^{2}/\Omega =1~A^{2}{\cdot }\Omega } ,} where ohm ( Ω {\displaystyle \Omega } ) is the SI derived unit of electrical resistance . The watt
540-452: The amount of current that generates a force of two dynes per centimetre of length between two wires one centimetre apart. The size of the unit was chosen so that the units derived from it in the MKSA system would be conveniently sized. The "international ampere" was an early realization of the ampere, defined as the current that would deposit 0.001 118 grams of silver per second from
570-485: The ampere was most accurately realised using a Kibble balance , but in practice the unit was maintained via Ohm's law from the units of electromotive force and resistance , the volt and the ohm , since the latter two could be tied to physical phenomena that are relatively easy to reproduce, the Josephson effect and the quantum Hall effect , respectively. Techniques to establish the realisation of an ampere had
600-410: The creation of modern electrical science, an international convention, signed at the 1881 International Exposition of Electricity , established the ampere as a standard unit of electrical measurement for electric current. The ampere was originally defined as one tenth of the unit of electric current in the centimetre–gram–second system of units . That unit, now known as the abampere , was defined as
630-515: The energy company Ørsted A/S uses the unit megawatt for produced electrical power and the equivalent unit megajoule per second for delivered heating power in a combined heat and power station such as Avedøre Power Station . When describing alternating current (AC) electricity, another distinction is made between the watt and the volt-ampere . While these units are equivalent for simple resistive circuits , they differ when loads exhibit electrical reactance . Radio stations usually report
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#1732798244664660-460: The maximum power output it can achieve at any point in time. A power station's annual energy output, however, would be recorded using units of energy (not power), typically gigawatt hours. Major energy production or consumption is often expressed as terawatt hours for a given period; often a calendar year or financial year. One terawatt hour of energy is equal to a sustained power delivery of one terawatt for one hour, or approximately 114 megawatts for
690-488: The power of their transmitters in units of watts, referring to the effective radiated power . This refers to the power that a half-wave dipole antenna would need to radiate to match the intensity of the transmitter's main lobe . The terms power and energy are closely related but distinct physical quantities. Power is the rate at which energy is generated or consumed and hence is measured in units (e.g. watts) that represent energy per unit time . For example, when
720-449: The rate at which work is done is one watt. 1 W = 1 J / s = 1 N ⋅ m / s = 1 k g ⋅ m 2 ⋅ s − 3 . {\displaystyle \mathrm {1~W=1~J{/}s=1~N{\cdot }m{/}s=1~kg{\cdot }m^{2}{\cdot }s^{-3}} .} In terms of electromagnetism , one watt
750-551: The rate of energy transfer . The watt is named in honor of James Watt (1736–1819), an 18th-century Scottish inventor , mechanical engineer , and chemist who improved the Newcomen engine with his own steam engine in 1776. Watt's invention was fundamental for the Industrial Revolution . When an object's velocity is held constant at one meter per second against a constant opposing force of one newton ,
780-569: The unit of power. In the electric power industry , megawatt electrical ( MWe or MW e ) refers by convention to the electric power produced by a generator, while megawatt thermal or thermal megawatt (MWt, MW t , or MWth, MW th ) refers to thermal power produced by the plant. For example, the Embalse nuclear power plant in Argentina uses a fission reactor to generate 2,109 MW t (i.e. heat), which creates steam to drive
810-570: The unit within the existing system of practical units as "the power conveyed by a current of an Ampère through the difference of potential of a Volt". In October 1908, at the International Conference on Electric Units and Standards in London, so-called international definitions were established for practical electrical units. Siemens' definition was adopted as the international watt. (Also used: 1 A × 1 Ω.) The watt
840-567: Was built in 1982 is 1,011 feet (308 m) tall and cost $ 13 million. The facility was owned by Allegheny Energy Supply before merging with Akron, Ohio based FirstEnergy in February 2011. The power plant was closed on September 1, 2012, by FirstEnergy, along with six other plants in the tri-county grid to comply with federal Environmental Protection Agency (EPA) guidelines that set new Mercury and Air Toxics Standards (MATS) and other environmental and air quality requirements. The decision
870-420: Was defined as equal to 10 units of power in the practical system of units. The "international units" were dominant from 1909 until 1948. After the 9th General Conference on Weights and Measures in 1948, the international watt was redefined from practical units to absolute units (i.e., using only length, mass, and time). Concretely, this meant that 1 watt was defined as the quantity of energy transferred in
900-402: Was made not to invest in some of the smaller plants considering it would be quite expensive to install a scrubber and other air pollution control upgrades to keep the plant in operation. Megawatt The watt (symbol: W ) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m ⋅s . It is used to quantify
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