Electricity

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Lightning is one of the most dramatic effects of electricity.

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Electromagnetism

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Electricity is the set of physical phenomena associated with the presence and

motion of matter that has a property of electric charge. In early days, electricity was
considered as being unrelated to magnetism. Later on, many experimental results
 and the development of Maxwell's equations indicated that both electricity and
magnetism are from a single phenomenon: electromagnetism. Various common
phenomena are related to electricity, including lightning, static electricity, electric
heating, electric discharges and many others.
The presence of an electric charge, which can be either positive or negative,
produces an electric field. The movement of electric charges is an electric
current and produces a magnetic field.
When a charge is placed in a location with a non-zero electric field, a force will act on
it. The magnitude of this force is given by Coulomb's law. Thus, if that charge were to
move, the electric field would be doing work on the electric charge. Thus we can
speak of electric potential at a certain point in space, which is equal to the work done
by an external agent in carrying a unit of positive charge from an arbitrarily chosen
reference point to that point without any acceleration and is typically measured
in volts.
Electricity is at the heart of many modern technologies, being used for:

 electric power where electric current is used to energise equipment;

 electronics which deals with electrical circuits that involve active electrical
components such as vacuum tubes, transistors, diodes and integrated circuits,
and associated passive interconnection technologies.
Electrical phenomena have been studied since antiquity, though progress in
theoretical understanding remained slow until the seventeenth and eighteenth
centuries. Even then, practical applications for electricity were few, and it would not
be until the late nineteenth century that electrical engineers were able to put it to
industrial and residential use. The rapid expansion in electrical technology at this
time transformed industry and society, becoming a driving force for the Second
Industrial Revolution. Electricity's extraordinary versatility means it can be put to an
almost limitless set of applications which
include transport, heating, lighting, communications, and computation. Electrical
power is now the backbone of modern industrial society. [1]

Contents

 1History
 2Concepts
o 2.1Electric charge
o 2.2Electric current
o 2.3Electric field
o 2.4Electric potential
o 2.5Electromagnets
o 2.6Electrochemistry
o 2.7Electric circuits
o 2.8Electric power
o 2.9Electronics
o 2.10Electromagnetic wave
 3Production and uses
o 3.1Generation and transmission
 o 3.2Applications
 4Electricity and the natural world
o 4.1Physiological effects
o 4.2Electrical phenomena in nature
 5Cultural perception
 6See also
 7Notes
 8References
 9External links

History

Thales, the earliest known researcher into electricity

Main articles: History of electromagnetic theory and History of electrical engineering

See also: Etymology of electricity
Long before any knowledge of electricity existed, people were aware of shocks
from electric fish. Ancient Egyptian texts dating from 2750 BCE referred to these fish
as the "Thunderer of the Nile", and described them as the "protectors" of all other
fish. Electric fish were again reported millennia later by ancient
Greek, Roman and Arabic naturalists and physicians.[2] Several ancient writers, such
as Pliny the Elder and Scribonius Largus, attested to the numbing effect of electric
shocks delivered by electric catfish and electric rays, and knew that such shocks
could travel along conducting objects. [3] Patients suffering from ailments such
as gout or headache were directed to touch electric fish in the hope that the powerful
jolt might cure them.[4] Possibly the earliest and nearest approach to the discovery of
the identity of lightning, and electricity from any other source, is to be attributed to
the Arabs, who before the 15th century had the Arabic word for lightning ra‘ad (‫)رعد‬
applied to the electric ray.[5]
Ancient cultures around the Mediterranean knew that certain objects, such as rods
of amber, could be rubbed with cat's fur to attract light objects like feathers. Thales of
Miletus made a series of observations on static electricity around 600 BCE, from
which he believed that friction rendered amber magnetic, in contrast to minerals such
as magnetite, which needed no rubbing.[6][7][8][9] Thales was incorrect in believing the
attraction was due to a magnetic effect, but later science would prove a link between
magnetism and electricity. According to a controversial theory, the Parthians may
have had knowledge of electroplating, based on the 1936 discovery of the Baghdad
Battery, which resembles a galvanic cell, though it is uncertain whether the artifact
was electrical in nature.[10]

Benjamin Franklin conducted extensive research on electricity in the 18th century, as documented

by Joseph Priestley (1767) History and Present Status of Electricity, with whom Franklin carried on
extended correspondence.

Electricity would remain little more than an intellectual curiosity for millennia until
1600, when the English scientist William Gilbert wrote De Magnete, in which he
made a careful study of electricity and magnetism, distinguishing the lodestone effect
from static electricity produced by rubbing amber.[6] He coined the New
Latin word electricus ("of amber" or "like amber", from ἤλεκτρον, elektron,
the Greek word for "amber") to refer to the property of attracting small objects after
being rubbed.[11] This association gave rise to the English words "electric" and
"electricity", which made their first appearance in print in Thomas
Browne's Pseudodoxia Epidemica of 1646.[12]
Further work was conducted in the 17th and early 18th centuries by Otto von
Guericke, Robert Boyle, Stephen Gray and C. F. du Fay.[13] Later in the 18th
century, Benjamin Franklin conducted extensive research in electricity, selling his
possessions to fund his work. In June 1752 he is reputed to have attached a metal
key to the bottom of a dampened kite string and flown the kite in a storm-threatened
sky.[14] A succession of sparks jumping from the key to the back of his hand showed
that lightning was indeed electrical in nature.[15] He also explained the apparently
paradoxical behavior[16] of the Leyden jar as a device for storing large amounts of
electrical charge in terms of electricity consisting of both positive and negative
charges.[13]
Michael Faraday's discoveries formed the foundation of electric motor technology

In 1791, Luigi Galvani published his discovery of bioelectromagnetics, demonstrating

that electricity was the medium by which neurons passed signals to the muscles.[17][18]
[13]
 Alessandro Volta's battery, or voltaic pile, of 1800, made from alternating layers of
zinc and copper, provided scientists with a more reliable source of electrical energy
than the electrostatic machines previously used.[17][18] The recognition
of electromagnetism, the unity of electric and magnetic phenomena, is due to Hans
Christian Ørsted and André-Marie Ampère in 1819–1820. Michael Faraday invented
the electric motor in 1821, and Georg Ohm mathematically analysed the electrical
circuit in 1827.[18] Electricity and magnetism (and light) were definitively linked
by James Clerk Maxwell, in particular in his "On Physical Lines of Force" in 1861 and
1862.[19]
While the early 19th century had seen rapid progress in electrical science, the late
19th century would see the greatest progress in electrical engineering. Through such
people as Alexander Graham Bell, Ottó Bláthy, Thomas Edison, Galileo
Ferraris, Oliver Heaviside, Ányos Jedlik, William Thomson, 1st Baron Kelvin, Charles
Algernon Parsons, Werner von Siemens, Joseph Swan, Reginald Fessenden, Nikola
Tesla and George Westinghouse, electricity turned from a scientific curiosity into an
essential tool for modern life.
In 1887, Heinrich Hertz[20]:843–44[21] discovered that electrodes illuminated with ultraviolet
light create electric sparks more easily. In 1905, Albert Einstein published a paper
that explained experimental data from the photoelectric effect as being the result of
light energy being carried in discrete quantized packets, energising electrons. This
discovery led to the quantum revolution. Einstein was awarded the Nobel Prize in
Physics in 1921 for "his discovery of the law of the photoelectric effect". [22] The
photoelectric effect is also employed in photocells such as can be found in solar
panels and this is frequently used to make electricity commercially.
The first solid-state device was the "cat's-whisker detector" first used in the 1900s in
radio receivers. A whisker-like wire is placed lightly in contact with a solid crystal
(such as a germanium crystal) to detect a radio signal by the contact junction effect.
[23]
 In a solid-state component, the current is confined to solid elements and
compounds engineered specifically to switch and amplify it. Current flow can be
understood in two forms: as negatively charged electrons, and as positively charged
electron deficiencies called holes. These charges and holes are understood in terms
of quantum physics. The building material is most often a crystalline semiconductor.
[24][25]
Solid-state electronics came into its own with the emergence
of transistor technology. The first working transistor, a germanium-based point-
contact transistor, was invented by John Bardeen and Walter Houser Brattain at Bell
Labs in 1947,[26] followed by the bipolar junction transistor in 1948.[27] These early
transistors were relatively bulky devices that were difficult to manufacture on a mass-
production basis.[28]:168 They were followed by the silicon-based MOSFET (metal-
oxide-semiconductor field-effect transistor, or MOS transistor), invented
by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959.[29][30][31] It was the first
truly compact transistor that could be miniaturised and mass-produced for a wide
range of uses,[28]:165,179 leading to the silicon revolution.[32] Solid-state devices started
becoming prevalent from the 1960s, with the transition from vacuum tubes to
semiconductor diodes, transistors, integrated circuit (IC) chips, MOSFETs, and light-
emitting diode (LED) technology.
The most common electronic device is the MOSFET, [30][33] which has become the most
widely manufactured device in history.[34] Common solid-state MOS devices
include microprocessor chips[35] and semiconductor memory.[36][37] A special type of
semiconductor memory is flash memory, which is used in USB flash
drives and mobile devices, as well as solid-state drive (SSD) technology to replace
mechanically rotating magnetic disc hard disk drive (HDD) technology.