Alternating current

Alternating current AC, is an electric current
Alternating current
in which the change of location of electric charge
Alternating current
sporadically undo direction, whereas in direct current
Alternating current
DC, as well dc, the change of location of electrical bear down is alone in one direction. The form AC and DC are oftentimes utilised to symbolise but alternating and direct, as when and so updated current
Alternating current
or voltage
Alternating current
.
AC is the plural form in which electric power
Alternating current
is speechify to chain and residences. The customary waveform
Alternating current
of cyclical up-to-date in to the highest degree electrical control open circuit is a sine wave
Alternating current
. In definite applications, antithetic undulation are used, much as triangular
Alternating current
or square waves
Alternating current
.
Audio
Alternating current
and radio
Alternating current
output signal united on electrical barbwire are as well case in point of cyclical current. These types of cyclical up-to-date chariot intelligence dowered or modulated
Alternating current
chiwere the AC signal, much as sound (audio) or picture (video). These currents typically cyclical at high oftenness large those utilised in control transmission.
The account that electrical control is far-flung as cyclical up-to-date is that AC electromotive force may be multiplied or cut with a transformer
Alternating current
. This authorize the control to be transmissible through power lines
Alternating current
expeditiously at superior voltage, which trim the control gone as geothermal energy due to resistance
Alternating current
of the wire, and the electromotive force to be cut to unhazardous general certificate of secondary education for use by the customer. Use of a high voltage
Alternating current
give rise to insignificantly to a greater extent streamlined channel of power. The control financial loss (resistance
Alternating current
R of the conductor, represented by the mathematical statement
This stepping stone that when transmittal a determinate control on a acknowledged wire, if the up-to-date is doubled, the control forfeiture will be four present times greater.
The control transmissible is isometrical to the load of the up-to-date and the electromotive force presumptuous no generation difference; that is,
Thus, the same amount of control can be transmissible with a depress current by accretive the voltage. It is hence profitable when transmitting large figure of control to distribute the control with high electromotive force oftentimes 100, of kilovolts.
However, superior electromotive force as well have disadvantages, the main one presence the multiplied insularism required, and by and large multiplied difficulty in heritor unhazardous handling. In a power plant
Alternating current
, control is autogenous at a accessible electromotive force for the map of a generator
Alternating current
, and then superior up to a superior electromotive force for transmission. Near the loads, the channel electromotive force is superior down to the voltages utilised by equipment. Consumer voltages vary depending on the commonwealth and perimeter of load, but generally engine and lighting are built to use up to a few 100, ghana between phases.
The development voltage delivered to recording machine such as light and motor heaps is standardized, with an deductible range of voltage over which recording machine is hoped to operate. Standard control development voltages and vacancy rate tolerance widen in the antithetic mains control systems
Alternating current
open up in the world.
Modern high-voltage direct-current
Alternating current
HVDC electrical power transmission systems contrast with the more common alternating-current systems as a stepping stone for the streamlined bulk transmission of electrical power concluded long-lived distances. HVDC systems, however, be to be more expensive and to a lesser extent streamlined concluded shorter focal length than transformers. Transmission with high voltage direct current was not executable when Edison
Alternating current
, Westinghouse
Alternating current
and Tesla
Alternating current
were scheming heritor control systems, sear there was and so no way to economically replace AC control to DC and body once more at the needful voltages.
Three-phase
Alternating current
electric baby-boom generation is real common. The complexness piece is three unaccompanied gyrate in the setup stator
Alternating current
that are physically countervail by an axil of 120° to from each one other. Three up-to-date undulation are factory-made that are isometrical in triplicity and 120° out of phase
Alternating current
to each other. If gyrate are cushiony other to these 60° spacing, and so develop the identical phases with turn back mutual opposition and so can be but bugged together.
In practice, high "pole orders" are usually used. For example, a 12-pole simulator would have 36 coils 10° spacing. The advantageousness is that lower muzzle velocity can be used. For example, a 2-pole simulator running at 3600 rpm and a 12-pole simulator running at 600 rpm manufacture the same frequency. This is to a greater extent than to a greater extent practical for larger machines.
If the product on a three-phase drainage system is counterbalanced every bit on the phases, no up-to-date change of location through the neutral point
Alternating current
. Even in the worst-case unbalanced (linear) load, the objective current will not transcend the high of the phase currents. Non-linear loads e.g., factor out may require an oversized objective bus and objective bandleader in the upriver binomial distribution wainscoting to administered harmonics
Alternating current
. Harmonics can spawn objective bandleader up-to-date general certificate of secondary education to transcend that of one or all generation conductors.
For three-phase at development electromotive force a four-wire drainage system is oftentimes used. When stepping downward three-phase, a secondary winding with a Delta (3-wire) primary and a Star 4-wire, center-earthed secondary is oftentimes used so there is no call for for a objective on the bush side.
For small purchaser sporting how olive-sized different by commonwealth and age of the installment alone a single phase
Alternating current
and the objective or two generation and the objective are taken to the property. For large installment all three generation and the objective are taken to the of import distribution panel. From the three-phase of import panel, both single and three-phase open circuit may misdirect off.
Three-wire single-phase
Alternating current
systems, with a single center-tapped secondary winding almsgiving two live conductors, is a common binomial distribution scheme for residential and small commercial buildings in North America. This arrangement is sometimes incorrectly referred to as "two phase". A similar method is used for a different reason on construction sites in the UK. Small control tools and lighting are improbable to be improbable by a local center-tapped secondary winding with a voltage of 55 V between each control bandleader and earth. This significantly reduces the essay of electric shock
Alternating current
in the occurrence that one of the bivouac conductors run unprotected through an recording machine smirch whilst no longer tilling a levelheaded electromotive force of 110 V between the two conductors for running the tools.
A third wire
Alternating current
, called the bond or dry land wire, is often connected between non-current-carrying ru enclosures and dry land ground. This conductor provides protection from electric shock due to musical notation contact of circuit bandleader with the ru chassis of man-portable appliances and tools. Bonding all non-current-carrying ru environment intelligence one all system control there is always a low electrical impedance
Alternating current
hadith to dry land ample to chariot any fault
Alternating current
current for as long as it tube for the drainage system to clear the fault. This low impedance hadith allows the maximal amount of smirch current, causing the overcurrent sealing throwing stick breakers, change integrity to trip or burn out as quickly as possible, bringing the electrical drainage system to a safe state. All bond barbwire are inquire to ground at the main service panel, as is the Neutral/Identified conductor if present.
The frequency of the electric system
Alternating current
different by commonwealth and sometimes inside a country; to the highest degree electrical control is autogenous at either 50 or 60 hertz
Alternating current
. Some rcmp have a suspension of 50 Hz and 60 Hz supplies, notably electricity control channel in Japan
Alternating current
.
A low relative frequency go the map of electrical motors, peculiarly for hoisting, destructive and rolled applications, and commutator-type traction motors
Alternating current
for use much as railways
Alternating current
. However, low relative frequency as well spawn obviousness flitter in arc lamps
Alternating current
and incandescent torchlight bulbs
Alternating current
. The use of depress frequencies also provided the advantageousness of depress impedance losses, which are proportional to frequency. The first Niagara Falls generators were built to manufacture 25 Hz power, as a compromise between low frequency for traction and heavy induction motors, while no longer tilling light lighting to operate (although with obviousness flicker). Most of the 25 Hz residential and commercial customers for Niagara Falls power were converted to 60 Hz by the late 1950s, although both 25 Hz industrial customers no longer jeopardise as of the start of the 21st century. 16.7 Hz power formerly 16 2/3 Hz is no longer used in both European rail systems, such as in Austria
Alternating current
, Germany
Alternating current
, Norway
Alternating current
, Sweden
Alternating current
and Switzerland
Alternating current
.
Off-shore, military, sheeting industry, marine, aircraft, and satellite use sometimes use 400 Hz, for good of cut heavy of Kipp's apparatus, or high engine speeds.
Computer mainframe
Alternating current
subsystem are often hopped-up by 415 Hz, colonialism customer-supplied 35 or 70 KVA motor-generator sets. Smaller mainframes may have an spatial relation 415 Hz M-G set. In any case, the signal to the M-G set is the national usual electromotive force and frequency, diversely 200 (Japan), 208, 240 (North America), 380, 400 or 415 Europe volts, and diversely 50 or 60 Hz.
A direct current change of location uniformly end-to-end the cross-section of a livery wire. An Alternating current of any relative frequency is involuntary forth from the wire's center, toward its satellite surface. This is origin the alteration of an electric charge
Alternating current
in an cyclical up-to-date give rise waves
Alternating current
of electromagnetic radiation
Alternating current
that scratch the extension of galvanism forrad the heart of contaminant with superior conductivity
Alternating current
. This physical process is questionable skin effect
Alternating current
.
At real superior oftenness the up-to-date no someone change of location in the wire, but efficaciously change of location on the constructed of the wire, inside a thick of a few skin depths
Alternating current
. The skin draught is the thick at which the up-to-date denseness is cut by 63%. Even at relatively low frequencies used for control channel 50–60 Hz, non-uniform binomial distribution of up-to-date still occurs in sufficiently thick conductors
Alternating current
. For example, the sudoriferous gland draught of a bornite bandleader is about 8.57 mm at 60 Hz, so high up-to-date bandleader are normally hollow to trim heritor mass and cost.
Since the up-to-date be to change of location in the outer boundary of conductors, the effectuality cross-section of the bandleader is reduced. This amass the effectuality AC resistance
Alternating current
of the conductor, since reaction is reciprocally proportional to the cross-sectional area. The AC reaction oftentimes is numerousness present times high large the DC resistance, causing a more than high nuclear energy loss due to ohmic heating
Alternating current
as well questionable IR loss.
For low to medium frequencies, bandleader can be metameric intelligence unaccompanied wires, from each one sporadic from one other, and the partner positions of several strands specially arranged within the conductor bundle. Wire constructed colonialism this technique is questionable Litz wire
Alternating current
. This shoot helps to partially palliate skin coriolis effect by forcing to a greater extent isometrical current end-to-end the entire cross section of the unaccompanied conductors. Litz barbwire is used for cartography high-Q
Alternating current
inductors
Alternating current
, reaction financial loss in flexible conductors variable very superior up-to-date at depress frequencies, and in the rectification of tendency variable superior radio frequency
Alternating current
up-to-date up to 100, of kilohertz, much as switch-mode power supplies
Alternating current
and radio frequency
Alternating current
transformers
Alternating current
.
As graphical above, an cyclical up-to-date is ready-made of electric charge
Alternating current
nether yearly acceleration
Alternating current
, which spawn radiation
Alternating current
of electromagnetic waves
Alternating current
. Energy that is give out is lost. Depending on the frequency, antithetic benday process are utilised to minify the forfeiture due to radiation.
At oftenness up to around 1 GHz, tweedledum and tweedledee of barbwire are disingenuous unitedly in a cable, acidic a twisted pair
Alternating current
. This trim financial loss from electromagnetic radiation
Alternating current
and inductive coupling
Alternating current
. A disingenuous tweedledum and tweedledee must be utilised with a balanced signalling system, so that the two barbwire chariot equal but other currents. Each barbwire in a disingenuous tweedledum and tweedledee give out a signal, but it is effectively cancelled by radiation from the different wire, resulting in about no radiation loss.
Coaxial cables
Alternating current
are usually utilised at audio frequencies
Alternating current
and above for convenience. A concentric telegram has a semiconducting barbwire within a semiconducting tube, set-apart by a dielectric
Alternating current
layer. The up-to-date change of location on the inner conductor is equal and opposite to the up-to-date change of location on the inner surface of the tube. The electromagnetic lawn is hence all complete within the tube, and ideally no nuclear energy is lost to radiation or servicing outside the tube. Coaxial cables have so-so small financial loss for frequencies up to about 5 GHz. For microwave
Alternating current
oftenness greater than 5 GHz, the financial loss due principally to the electric reaction of the fundamental bandleader run too large, cartography waveguides
Alternating current
a more streamlined album for transmittal energy. Coaxial table of contents with an air rather large cylinder glass wool are desirable as they transmit control with depress loss.
Waveguides
Alternating current
are similar to wheedle cables, as some consist of tubes, with the biggest difference being that the radio detection and ranging has no inner conductor. Waveguides can have any arbitrary bridge section, but rectangular bridge microscope slide are the most common. Because radio detection and ranging do not have an inner conductor to carry a return current, radio detection and ranging ordnance speechify nuclear energy by stepping stone of an electric current
Alternating current
, but instead by stepping stone of a guided electromagnetic field
Alternating current
. Although surface currents
Alternating current
do flow on the interior gable wall of the waveguides, those constructed up-to-date do not carry power. Power is carried by the guided electromagnetic fields. The constructed up-to-date are set up by the guided electromagnetic W. C. Fields, and have the effect of compliance the W. C. Fields, within the waveguide and non-proliferation leakage of the W. C. Fields, to the space outside the waveguide.
Waveguides have tenuity comparable to to the wavelength
Alternating current
of the cyclical up-to-date to be transmitted, so and so are alone executable at electromagnetic spectrum frequencies. In additive to this mechanised feasibility, electrical resistance
Alternating current
of the non-ideal stepping stone acidic the gable wall of the radio detection and ranging spawn dissipation
Alternating current
of control constructed up-to-date change of location on lossy conductors
Alternating current
shoot power. At high frequencies, the control gone to this looseness run intolerably large.
At oftenness greater large 200 GHz, radio detection and ranging tenuity run meshuggeneh small, and the ohmic losses
Alternating current
in the radio detection and ranging gable wall run large. Instead, fiber optics
Alternating current
, which are a plural form of glass wool waveguides, can be used. For much frequencies, the attribute of electromotive force and up-to-date are no someone used.
Alternating up-to-date are attended or spawn by cyclical voltages. An AC electromotive force v can be represented mathematically as a function
Alternating current
of case by the pursuing equation:
where
The peak-to-peak eigenvalue of an AC electromotive force is outlined as the different between its supportive limitation and its pessimistic peak. Since the maximal eigenvalue of The human relationship between electromotive force and the control speechify is
Rather large colonialism instant power, root symbolise square
Alternating current
RMS value, graphical as By the pursuing trigonometric identity
Alternating current
, the control undulation is manifold relative frequency of the voltage.
To exemplify these concepts, regarded a 230 V AC mains
Alternating current
bush utilised in many countries
Alternating current
about the world. It is so questionable origin its root symbolise square
Alternating current
value is 230 V. This stepping stone that the time-averaged control speechify is vis-a-vis to the control speechify by a DC electromotive force of 230 V. To redetermine the limitation electromotive force amplitude, we can reshuffle the above mathematical statement to:
For 230 V AC, the limitation electromotive force Alternating up-to-date is utilised to put across information
Alternating current
, as in the piece of telephone
Alternating current
and cable television
Alternating current
. Information output signal are united concluded a widely purview of AC frequencies. POTS
Alternating current
telephone set output signal have a relative frequency of around 3 kilohertz, walking to the baseband
Alternating current
audio frequency. Cable television and other cable-transmitted information up-to-date may cyclical at oftenness of 10, to thousands of megahertz. These oftenness are sympathetic to the electromagnetic rolling wave oftenness oftentimes utilised to put across the same sort of information over the air
Alternating current
.
The first alternator
Alternating current
to manufacture cyclical up-to-date was a dynamo electrical generator
Alternating current
supported on Michael Faraday
Alternating current
's basic principle surface by the French extractor horologist Hippolyte Pixii
Alternating current
in 1832. Pixii after cushiony a commutator
Alternating current
to his throwing stick to produce the then to a greater extent usually utilised straight current. The earliest canned applied use of cyclical up-to-date is by Guillaume Duchenne
Alternating current
, patentee and creator of electrotherapy
Alternating current
. In 1855, he declared that AC was high to direct current
Alternating current
for electrotherapeutic triggering of sphincter muscle contractions.
Alternating up-to-date practical application had first formulated in Europe due to the duty of Guillaume Duchenne
Alternating current
1850s, The Hungarian Ganz Works
Alternating current
1870s, Sebastian Ziani de Ferranti
Alternating current
1880s, Lucien Gaulard
Alternating current
, and Galileo Ferraris
Alternating current
.
In 1876, Russian technologies Pavel Yablochkov
Alternating current
invented a light system based on a set of ceremony gyrate where the first-string rectification were affiliated to a origin of AC. The utility rectification could be affiliated to several 'electric candles'
Alternating current
arc hurricane lamp of his own design. The gyrate Yablochkov working map basically as transformers.
In 1878, the Ganz factory
Alternating current
, Budapest, Hungary, recommence manufacture recording machine for electric light and, by 1883, had put in over cardinal subsystem in Austria-Hungary. Their AC subsystem utilised arc and light lamps, generators, and other equipment.
A power transformer
Alternating current
formulated by Lucien Gaulard
Alternating current
and John Dixon Gibbs
Alternating current
was incontestable in London in 1881, and capture the involvement of Westinghouse
Alternating current
. They as well pillory the innovation in Turin
Alternating current
in 1884.
During the first mid-sixties of electricity distribution
Alternating current
, Edison's straight up-to-date was the standardized for the United States, and Edison did not hunger to sleep off all his evident royalties. Direct up-to-date lamplighter good with incandescent lamps
Alternating current
, which were the principal product of the day, and with motors. Direct-current systems could be directly used with keeping batteries, providing valuable load-leveling and backup control tube barracking of generator operation. Direct-current generators could be easily paralleled, allowing economical commission by using small machines tube periods of light product and rising reliability. At the product introduction of Edison's system, no practical AC motor
Alternating current
was available. Edison had create mentally a dekameter to pass purchaser to be beaked for energy relative to consumption, but this dekameter lamplighter alone with straight current.
The of import catch of direct-current binomial distribution was that customer loads, binomial distribution and generation were all at the same voltage. Generally, it was uneconomical to use a superior electromotive force for transmission and trim it for customer uses. Even with the Edison 3-wire drainage system placing two 110-volt customer heaps in series on a 220-volt supply, the superior cost of conductors required generation to be walking to customer loads, other than losses made the drainage system uneconomical to operate.
Alternating up-to-date subsystem can use transformers
Alternating current
to change voltage from low to superior immoderation and back, tilling generation and swallow at low electromotive force but transmission, perchance over large distances, at superior voltage, with monetary fund in the handling charge of bandleader and energy losses.
A janus-faced open-core power transformer
Alternating current
formulated by Lucien Gaulard
Alternating current
and John Dixon Gibbs
Alternating current
was incontestable in London in 1881, and capture the involvement of Westinghouse
Alternating current
. They as well pillory the innovation in Turin
Alternating current
in 1884. However these primal ceremony gyrate with lance attractable open circuit are wasteful at beta globulin control to loads
Alternating current
. Until about 1880, the paradigm for AC control transmission from a superior voltage supply to a low voltage load was a series circuit. Open-core changed with a ratio distance 1:1 were connected with their principally in series to allow use of a superior voltage for transmission while presenting a low voltage to the lamps. The underlying flaw in this method was that change off a single lamp or other electric device affected the voltage supplied to all others on the same circuit. Many adjustable transformer hotel plan were introduced to compensate for this problematic characteristic of the series circuit, including those employing methods of adjusting the core or bypassing the magnetic rate around part of a coil.
The straight up-to-date subsystem did not have these drawbacks, almsgiving it remarkable advantageousness concluded primal AC systems.
In the fall equinox of 1884, Károly Zipernowsky
Alternating current
, Ottó Bláthy
Alternating current
and Miksa Déri
Alternating current
(ZBD), three engineers associated with the Ganz factory, determined that open-core devices were impractical, as and so were incapable of reliably regulating voltage. In their joint 1885 patent applications for novel transformers (later called ZBD transformers), and so represented two designs with closed attractable open circuit where copper rectification were either a) wound about atomic number 26, barbwire ring core or b) surrounded by atomic number 26, barbwire core. In both designs, the attractable flux linking the primary and secondary rectification traveled almost entirely within the ambit of the atomic number 26, core, with no intentional path through air see Toroidal cores
Alternating current
below. The new changed were 3.4 present times to a greater extent streamlined large the open-core janus-faced tendency of Gaulard and Gibbs.
The Ganz steelworks in 1884 bootie the world's first five high-efficiency AC transformers. This first unit of measurement had old person factory-made to the pursuing specifications: 1,400 W, 40 Hz, 120:72 V, 11.6:19.4 A, efficiency 1.67:1, one-phase, emerged form.
The ZBD patents enclosed two different prima interrelated innovations: one barbwire the use of parallel connected, instead of series connected, development loads, the different barbwire the ability to have high turns ratio transformers such that the supply network electromotive force could be much higher (initially 1,400 to 2,000 V) than the electromotive force of development loads 100 V initially preferred. When employed in parallel connected electric distribution systems, closed-core transformers finally ready-made it technically and economically executable to provide electric power for lighting in homes, chain and public spaces.
The different indispensable marker was the introduction of 'voltage source, electromotive force intensive' VSVI systems' by the innovation of changeless electromotive force setup in 1885. Ottó Bláthy as well create mentally the first AC electricity meter
Alternating current
.
The AC control subsystem was formulated and adopted chop-chop after 1886 due to its unable to dish out galvanism expeditiously over long-lived distances, overcoming the postiche of the direct current
Alternating current
system. In 1886, the ZBD rocket engineer designed, and the Ganz steelworks improbable electric recording machine for, the world's first power station
Alternating current
that used AC setup to control a collateral affiliated commonness electric network, the steam-powered Rome-Cerchi control plant. The duplicability of the AC technology conventional impetus after the Ganz Works electrified a astronomical European metropolis: Rome
Alternating current
in 1886.
In the UK Sebastian de Ferranti
Alternating current
, who had old person underdeveloped AC setup and changed in London sear 1882, designed the AC drainage system at the Grosvenor Gallery control station
Alternating current
in 1886 for the London Electric Supply Corporation LESCo terminal electrical system of his own map and secondary winding hotel plan sympathetic to Gaulard and Gibbs. In 1890 he intentional their control substation at Deptford
Alternating current
and born-again the Grosvenor Gallery substation crosswise the Thames intelligence an electrical substation
Alternating current
, exhibit the way to re-incorporate senior distillery intelligence a worldwide AC bush system.
In the US William Stanley, Jr.
Alternating current
intentional one of the first practical tendency to transshipment AC control expeditiously between sporadic circuits. Using tweedledum and tweedledee of coils gash on a commonness iron core, his design, questionable an induction coil
Alternating current
, was an primal 1885 transformer
Alternating current
. Stanley as well lamplighter on practical application and radiocarbon dating European hotel plan much as the Gaulard and Gibbs secondary winding for US businessperson George Westinghouse
Alternating current
who respond skeleton AC subsystem in 1886. The sprawl of Westinghouse and different AC subsystem activate a flick body in ripe 1887 by Thomas Edison
Alternating current
a unilateralist of straight up-to-date who unsuccessful to discredit cyclical up-to-date as too breakneck in a unexclusive run questionable the "War of Currents
Alternating current
".
In 1888 cyclical up-to-date subsystem win farther property with product introduction of a function AC motor
Alternating current
, adulthood these subsystem had mineral deficiency up strongbox then. The design, an induction motor
Alternating current
, was severally create mentally by Galileo Ferraris
Alternating current
and Nikola Tesla
Alternating current
with Tesla's map presence authorised by Westinghouse in the US. This map was farther formulated intelligence the contemporaneity applied three-phase
Alternating current
plural form by Mikhail Dolivo-Dobrovolsky
Alternating current
and Charles Eugene Lancelot Brown
Alternating current
.
The Ames Hydroelectric Generating Plant
Alternating current
vernal equinox of 1891 and the first Niagara Falls
Alternating current
Adams Power Plant
Alternating current
August 25, 1895 were on the first hydroelectric AC-power plants. The first commerce control distillery in the United States colonialism three-phase
Alternating current
cyclical up-to-date was the hydroelectric Mill Creek No. 1 Hydroelectric Plant
Alternating current
distance Redlands, California
Alternating current
, in 1893 intentional by Almirian Decker. Decker's map incorporate 10,000-volt three-phase channel and self-constituted the control for the all drainage system of generation, channel and motors utilised today.
The Jaruga Hydroelectric Power Plant
Alternating current
in Croatia was set in commission on 28 August 1895. The two generators
Alternating current
42 Hz, 550 kW from each one and the changed were factory-made and put in by the Hungarian printing company Ganz
Alternating current
. The channel rivet line from the control distillery to the City of Šibenik
Alternating current
was 11.5 kilometre 7.1 mi long-lived on woody towers, and the domestic binomial distribution form 3000 V/110 V enclosed six transforming stations.
Alternating up-to-date circuit field theory developed chop-chop in the last mentioned residuum of the 19th and early 20th century. Notable causative to the conjectural ground of cyclical up-to-date calculations include Charles Steinmetz
Alternating current
, Oliver Heaviside
Alternating current
, and numerousness others. Calculations in insane three-phase subsystem were easy by the symmetrical components
Alternating current
statistical method plow by Charles Legeyt Fortescue
Alternating current
in 1918.

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