ELECTRICAL ENGG.----PAST AND PRESENT PART I
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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. Electricity is related to magnetism, both
being part of the phenomenon of electromagnetism, as described by Maxwell's equations. James Clerk
Maxwell (13 June 1831 – 5 November 1879) was a Scottish scientist in the field of mathematical physics.
His most notable achievement was to formulate the classical theory of electromagnetic radiation,
bringing together for the first time electricity, magnetism, and light as different manifestations of the
same phenomenon. Maxwell's equations for electromagnetism have been called the "second great
unification in physics" where the first one had been realised by Isaac Newton. Sir Isaac Newton (25
December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, theologian,
and author (described in his own day as a "natural philosopher") who is widely recognised as one of the
most influential scientists of all time and as a key figure in the scientific revolution. His book
Mathematical Principles of Natural Philosophy, first published in 1687, established classical mechanics.
Newton also made seminal contributions to optics, and shares credit with Gottfried Wilhelm Leibniz for
developing the infinitesimal calculus. Gottfried Wilhelm (von) Leibniz( 1 July 1646 – 14 November
1716) was a prominent German polymath and one of the most important logicians, mathematicians and
natural philosophers of the Enlightenment. As a representative of the seventeenth-century tradition of
rationalism, Leibniz developed, as his most prominent accomplishment, the ideas of differential and
integral calculus, independently of Isaac Newton's contemporaneous developments. Mathematical
works have consistently favored Leibniz's notation as the conventional expression of calculus. It was
only in the 20th century that Leibniz's law of continuity and transcendental law of homogeneity found
mathematical implementation (by means of non-standard analysis). He became one of the most prolific
inventors in the field of mechanical calculators. While working on adding automatic multiplication and
division to Pascal's calculator, he was the first to describe a pinwheel calculator in 1685 and invented
the Leibniz wheel, used in the arithmometer, the first mass-produced mechanical calculator. He also
refined the binary number system, which is the foundation of nearly all digital (electronic, solid-state,
discrete logic) computers, including the Von Neumann machine, which is the standard design paradigm,
or "computer architecture", followed from the second half of the 20th century, and into the 21st.
Various common phenomena are related to electricity, including
lightning, static electricity, electric heating, electric discharges and many others.
Long before any knowledge of electricity existed, people were
aware of shocks from electric fish. Ancient Egyptian texts dating from 2750 BC 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.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. 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.
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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 BC, from which he believed that friction
rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing. Thales
of Miletus ( c. 624/623 – c. 548/545 BC) was a Greek mathematician, astronomer and pre-Socratic
philosopher from Miletus in Ionia, Asia Minor. He was one of the Seven Sages of Greece. Many, most
notably Aristotle, regarded him as the first philosopher in the Greek tradition, and he is otherwise
historically recognized as the first individual in Western civilization known to have entertained and
engaged in scientific philosophy. Aristotle ( 384–322 BC) was a Greek philosopher and polymath during
the Classical period in Ancient Greece. Taught by Plato, he was the founder of the Lyceum, the
Peripatetic school of philosophy, and the Aristotelian tradition. Plato in Classical Attic (424/423 –
348/347 BC) was an Athenian philosopher during the Classical period in Ancient Greece, founder of the
Platonist school of thought, and the Academy, the first institution of higher learning in the Western
world. His writings cover many subjects including physics, biology, zoology, metaphysics, logic, ethics,
aesthetics, poetry, theatre, music, rhetoric, psychology, linguistics, economics, politics, and government.
Aristotle provided a complex synthesis of the various philosophies existing prior to him. It was above all
from his teachings that the West inherited its intellectual lexicon, as well as problems and methods of
inquiry. As a result, his philosophy has exerted a unique influence on almost every form of knowledge in
the West and it continues to be a subject of contemporary philosophical discussion.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.
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. Benjamin Franklin (January 17, 1706 – April
17, 1790) was a British American polymath and one of the Founding Fathers of the United States.
Franklin was a leading writer, printer, political philosopher, politician, Freemason, postmaster, scientist,
inventor, humorist, civic activist, statesman, and diplomat. As a scientist, he was a major figure in the
American Enlightenment and the history of physics for his discoveries and theories regarding electricity.
As an inventor, he is known for the lightning rod, bifocals, and the Franklin stove, among other
inventions. He founded many civic organizations, including the Library Company, Philadelphia's first fire
department, and the University of Pennsylvania.
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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. William Gilbert (24 May 1544?-30 November
1603), also known as Gilberd, was an English physician, physicist and natural philosopher. He
passionately rejected both the prevailing Aristotelian philosophy and the Scholastic method of university
teaching. He is remembered today largely for his book De Magnete (1600 ) .A unit of magnetomotive
force, also known as magnetic potential, was named the Gilbert in his honour. 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. 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.
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Further work was conducted in the 17th and early 18th
centuries by Otto von Guericke, Robert Boyle, Stephen Gray and C. F. du Fay. 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. A succession of sparks jumping from the key to the back of his
hand showed that lightning was indeed electrical in nature. He also explained the apparently paradoxical
behavior 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. Half-length portrait oil painting of a man in a
dark suit Michael Faraday's discoveries formed the foundation of electric motor technology. Michael
Faraday (22 September 1791 – 25 August 1867) was an English scientist who contributed to the study of
electromagnetism and electrochemistry. His main discoveries include the principles underlying
electromagnetic induction, diamagnetism and electrolysis.
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In 1791, Luigi Galvani published his discovery of
bioelectromagnetics, demonstrating that electricity was the medium by which neurons passed signals to
the muscles. Luigi Galvani (9 September 1737 – 4 December 1798) was an Italian physician, physicist,
biologist and philosopher, who discovered animal electricity. He is recognized as the pioneer of
bioelectromagnetics. In 1780, he and his wife Lucia discovered that the muscles of dead frogs' legs
twitched when struck by an electrical spark. This was one of the first forays into the study of
bioelectricity, a field that studies the electrical patterns and signals from tissues such as the nerves and
muscles. 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. Alessandro Giuseppe Antonio Anastasio Volta (18 February 1745 – 5 March
1827) was an Italian physicist, chemist, and pioneer of electricity and power who is credited as the
inventor of the electric battery and the discoverer of methane. He invented the Voltaic pile in 1799, and
reported the results of his experiments in 1800 in a two-part letter to the President of the Royal Society.
With this invention Volta proved that electricity could be generated chemically and debunked the
prevalent theory that electricity was generated solely by living beings. Volta's invention sparked a great
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amount of scientific excitement and led others to conduct similar experiments which eventually led to
the development of the field of electrochemistry. The recognition of electromagnetism, the unity of
electric and magnetic phenomena, is due to Hans Christian Ørsted and André-Marie Ampère in 1819–
1820. Hans Christian; often rendered Oersted in English; (14 August 1777 – 9 March 1851) was a Danish
physicist and chemist who discovered that electric currents create magnetic fields, which was the first
connection found between electricity and magnetism. Oersted's law and the oersted (Oe) are named
after him. André-Marie Ampère (20 January 1775 – 10 June 1836)[2] was a French physicist and
mathematician who was one of the founders of the science of classical electromagnetism, which he
referred to as "electrodynamics". He is also the inventor of numerous applications, such as the solenoid
(a term coined by him) and the electrical telegraph. An autodidact, Ampère was a member of the French
Academy of Sciences and professor at the École polytechnique and the Collège de France. The SI unit of
measurement of electric current, the ampere, is named after him. His name is also one of the 72 names
inscribed on the Eiffel Tower.
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Michael Faraday invented the electric motor in 1821, and
Georg Ohm mathematically analysed the electrical circuit in 1827. Georg Simon Ohm (16 March 1789 –
6 July 1854) was a German physicist and mathematician. As a school teacher, Ohm began his research
with the new electrochemical cell, invented by Italian scientist Alessandro Volta. Using equipment of his
own creation, Ohm found that there is a direct proportionality between the potential difference
(voltage) applied across a conductor and the resultant electric current. This relationship is known as
Ohm's law. 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.
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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. Alexander Graham Bell (March 3, 1847 – August 2, 1922) was a
Scottish-born inventor, scientist, and engineer who is credited with inventing and patenting the first
practical telephone. He also co-founded the American Telephone and Telegraph Company (AT&T) in
1885. Thomas Alva Edison (February 11, 1847 – October 18, 1931) was an American inventor and
businessman who has been described as America's greatest inventor. He developed many devices in
fields such as electric power generation, mass communication, sound recording, and motion pictures.
These inventions, which include the phonograph, the motion picture camera, and early versions of the
electric light bulb, have had a widespread impact on the modern industrialized world. He was one of the
first inventors to apply the principles of organized science and teamwork to the process of invention,
working with many researchers and employees. He established the first industrial research laboratory.
Ernst Werner Siemens (13 December 1816 – 6 December 1892) was a German electrical engineer,
inventor and industrialist. Siemens's name has been adopted as the SI unit of electrical conductance, the
siemens. He founded the electrical and telecommunications conglomerate Siemens.
Nikola Tesla (10 July 1856 – 7 January 1943) was a Serbian-American inventor, electrical engineer,
mechanical engineer, and futurist best known for his contributions to the design of the modern
alternating current (AC) electricity supply system. George Westinghouse Jr. (October 6, 1846 – March
12, 1914) was an American entrepreneur and engineer based in Pennsylvania who created the railway
air brake and was a pioneer of the electrical industry, receiving his first patent at the age of 19.
Westinghouse saw the potential of using alternating current for electric power distribution in the early
1880s and put all his resources into developing and marketing it. This put Westinghouse's business in
direct competition with Thomas Edison, who marketed direct current for electric power distribution. In
1911 Westinghouse received the American Institute of Electrical Engineers's (AIEE) Edison Medal "For
meritorious achievement in connection with the development of the alternating current system."
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In 1887, Heinrich Hertz: discovered that electrodes illuminated with
ultraviolet light create electric sparks more easily. Heinrich Rudolf Hertz (22 February 1857 – 1 January
1894) was a German physicist who first conclusively proved the existence of the electromagnetic waves
predicted by James Clerk Maxwell's equations of electromagnetism. The unit of frequency, cycle per
second, was named the "hertz" in his honor. 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. Albert Einstein (14 March 1879 – 18 April 1955) was a
German-born theoretical physicist who developed the theory of relativity, one of the two pillars of
modern physics (alongside quantum mechanics).His work is also known for its influence on the
philosophy of science. He is best known to the general public for his mass–energy equivalence formula E
= mc2, which has been dubbed "the world's most famous equation". He received the 1921 Nobel Prize in
Physics "for his services to theoretical physics, and especially for his discovery of the law of the
photoelectric effect", a pivotal step in the development of quantum theory. 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". 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. 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.
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, followed by
the bipolar junction transistor in 1948. These early transistors were relatively bulky devices that were
difficult to manufacture on a mass-production basis.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. It was the first truly compact transistor that could be
miniaturised and mass-produced for a wide range of uses, leading to the silicon revolution.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.
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The most common electronic device is the MOSFET, which has
become the most widely manufactured device in history. Common solid-state MOS devices include
microprocessor chips and semiconductor memory. 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.
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The presence of charge gives rise to an electrostatic force:
charges exert a force on each other, an effect that was known, though not understood, in antiquity.A
lightweight ball suspended from a string can be charged by touching it with a glass rod that has itself
been charged by rubbing with a cloth. If a similar ball is charged by the same glass rod, it is found to
repel the first: the charge acts to force the two balls apart. Two balls that are charged with a rubbed
amber rod also repel each other. However, if one ball is charged by the glass rod, and the other by an
amber rod, the two balls are found to attract each other. These phenomena were investigated in the
late eighteenth century by Charles-Augustin de Coulomb, who deduced that charge manifests itself in
two opposing forms. This discovery led to the well-known axiom: like-charged objects repel and
opposite-charged objects attract. Charles-Augustin de Coulomb (14 June 1736 – 23 August 1806) was a
French military engineer and physicist. He is best known as the eponymous discoverer of what is now
called Coulomb's law, the description of the electrostatic force of attraction and repulsion, though he
also did important work on friction.The SI unit of electric charge, the coulomb, was named in his honor
in 1880.
The process by which electric current passes through a
material is termed electrical conduction, and its nature varies with that of the charged particles and the
material through which they are travelling. Examples of electric currents include metallic conduction,
where electrons flow through a conductor such as metal, and electrolysis, where ions (charged atoms)
flow through liquids, or through plasmas such as electrical sparks. While the particles themselves can
move quite slowly, sometimes with an average drift velocity only fractions of a millimetre per second,
the electric field that drives them itself propagates at close to the speed of light, enabling electrical
signals to pass rapidly along wires.
Current causes several observable effects, which
historically were the means of recognising its presence. That water could be decomposed by the current
from a voltaic pile was discovered by Nicholson and Carlisle in 1800, a process now known as
electrolysis. Their work was greatly expanded upon by Michael Faraday in 1833. Current through a
resistance causes localised heating, an effect James Prescott Joule studied mathematically in 1840.
James Prescott Joule FRS FRSE ( 24 December 1818 – 11 October 1889) was an English physicist,
mathematician and brewer, born in Salford, Lancashire. Joule studied the nature of heat, and discovered
its relationship to mechanical work (see energy). This led to the law of conservation of energy, which in
turn led to the development of the first law of thermodynamics. The SI derived unit of energy, the joule,
is named after him.
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He worked with Lord Kelvin to develop an absolute
thermodynamic temperature scale, which came to be called the Kelvin scale. William Thomson, 1st
Baron Kelvin (26 June 1824 – 17 December 1907) was a British mathematical physicist and engineer
born in Belfast.Professor of Natural Philosophy at the University of Glasgow for 53 years, he did
important work in the mathematical analysis of electricity and formulation of the first and second laws
of thermodynamics, and did much to unify the emerging discipline of physics in its modern form. He
received the Royal Society's Copley Medal in 1883, was its President 1890–1895, and in 1892 was the
first British scientist to be elevated to the House of Lords.
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Joule
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observations
of
magnetostriction, and he found the relationship between the current through a resistor and the heat
dissipated, which is also called Joule's first law. His experiments about energy transformations were first
published in 1843.One of the most important discoveries relating to current was made accidentally by
Hans Christian Ørsted in 1820, when, while preparing a lecture, he witnessed the current in a wire
disturbing the needle of a magnetic compass. He had discovered electromagnetism, a fundamental
interaction between electricity and magnetics. The level of electromagnetic emissions generated by
electric arcing is high enough to produce electromagnetic interference, which can be detrimental to the
workings of adjacent equipment.
The movement of electric charge is known as an electric
current, the intensity of which is usually measured in amperes. Current can consist of any moving
charged particles; most commonly these are electrons, but any charge in motion constitutes a current.
Electric current can flow through some things, electrical conductors, but will not flow through an
electrical insulator.
The concept of the electric field was introduced by
Michael Faraday. An electric field is created by a charged body in the space that surrounds it, and results
in a force exerted on any other charges placed within the field. The electric field acts between two
charges in a similar manner to the way that the gravitational field acts between two masses, and like it,
extends towards infinity and shows an inverse square relationship with distance. However, there is an
important difference. Gravity always acts in attraction, drawing two masses together, while the electric
field can result in either attraction or repulsion. Since large bodies such as planets generally carry no net
charge, the electric field at a distance is usually zero. Thus gravity is the dominant force at distance in
the universe, despite being much weaker.
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The concept of electric potential is closely linked to that of
the electric field. A small charge placed within an electric field experiences a force, and to have brought
that charge to that point against the force requires work. The electric potential at any point is defined as
the energy required to bring a unit test charge from an infinite distance slowly to that point. It is usually
measured in volts, and one volt is the potential for which one joule of work must be expended to bring a
charge of one coulomb from infinity. This definition of potential, while formal, has little practical
application, and a more useful concept is that of electric potential difference, and is the energy required
to move a unit charge between two specified points. An electric field has the special property that it is
conservative, which means that the path taken by the test charge is irrelevant: all paths between two
specified points expend the same energy, and thus a unique value for potential difference may be
stated.The volt is so strongly identified as the unit of choice for measurement and description of electric
potential difference thØrsted's discovery in 1821 that a magnetic field existed around all sides of a wire
carrying an electric current indicated that there was a direct relationship between electricity and
magnetism. Moreover, the interaction seemed different from gravitational and electrostatic forces, the
two forces of nature then known. The force on the compass needle did not direct it to or away from the
current-carrying wire, but acted at right angles to it. Ørsted's words were that "the electric conflict acts
in a revolving manner." The force also depended on the direction of the current, for if the flow was
reversed, then the force did too.at the term voltage sees greater everyday usage.
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The ability of chemical reactions to produce electricity, and
conversely the ability of electricity to drive chemical reactions has a wide array of uses.
Electrochemistry has always been an important part of
electricity. From the initial invention of the Voltaic pile, electrochemical cells have evolved into the
many different types of batteries, electroplating and electrolysis cells. Aluminium is produced in vast
quantities this way, and many portable devices are electrically powered using rechargeable cells.
The components in an electric circuit can take many forms,
which can include elements such as resistors, capacitors, switches, transformers and electronics.
Electronic circuits contain active components, usually semiconductors, and typically exhibit non-linear
behaviour, requiring complex analysis. The simplest electric components are those that are termed
passive and linear: while they may temporarily store energy, they contain no sources of it, and exhibit
linear responses to stimuli.
Electric power is the rate at which electric energy is transferred by
an electric circuit. The SI unit of power is the watt, one joule per second.
Electric power, like mechanical power, is the rate of doing work,
measured in watts, and represented by the letter P. The term wattage is used colloquially to mean
"electric power in watts."
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Electronics deals with electrical circuits that involve active
electrical components such as vacuum tubes, transistors, diodes, optoelectronics, sensors and
integrated circuits, and associated passive interconnection technologies. The nonlinear behaviour of
active components and their ability to control electron flows makes amplification of weak signals
possible and electronics is widely used in information processing, telecommunications, and signal
processing. The ability of electronic devices to act as switches makes digital information processing
possible. Interconnection technologies such as circuit boards, electronics packaging technology, and
other varied forms of communication infrastructure coFaraday's and Ampère's work showed that a
time-varying magnetic field acted as a source of an electric field, and a time-varying electric field was a
source of a magnetic field. Thus, when either field is changing in time, then a field of the other is
necessarily induced. Such a phenomenon has the properties of a wave, and is naturally referred to as an
electromagnetic wave. Electromagnetic waves were analysed theoretically by James Clerk Maxwell in
1864. Maxwell developed a set of equations that could unambiguously describe the interrelationship
between electric field, magnetic field, electric charge, and electric current. He could moreover prove
that such a wave would necessarily travel at the speed of light, and thus light itself was a form of
electromagnetic radiation. Maxwell's Laws, which unify light, fields, and charge are one of the great
milestones of theoretical physics complete ciIn the 6th century BC, the Greek philosopher Thales of
Miletus experimented with amber rods and these experiments were the first studies into the production
of electrical energy. While this method, now known as the triboelectric effect, can lift light objects and
generate sparks, it is extremely inefficient. It was not until the invention of the voltaic pile in the
eighteenth century that a viable source of electricity became available. The voltaic pile, and its modern
descendant, the electrical battery, store energy chemically and make it available on demand in the form
of electrical energy. The battery is a versatile and very common power source which is ideally suited to
many applications, but its energy storage is finite, and once discharged it must be disposed of or
recharged. For large electrical demands electrical energy must be generated and transmitted
continuously over conductive transmission lines.circuit functionality and transform the mixed
components into a regular working system.
Electricity is a very convenient way to transfer
energy, and it has been adapted to a huge, and growing, number of uses. The invention of a practical
incandescent light bulb in the 1870s led to lighting becoming one of the first publicly available
applications of electrical power. Although electrification brought with it its own dangers, replacing the
naked flames of gas lighting greatly reduced fire hazards within homes and factories. Public utilities
were set up in many cities targeting the burgeoning market for electrical lighting. In the late 20th
century and in modern times, the trend has started to flow in the direction of deregulation in the
electrical power sector.
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A voltage applied to a human body causes an electric
current through the tissues, and although the relationship is non-linear, the greater the voltage, the
greater the current.The threshold for perception varies with the supply frequency and with the path of
the current, but is about 0.1 mA to 1 mA for mains-frequency electricity, though a current as low as a
microamp can be detected as an electrovibration effect under certain conditions. If the current is
sufficiently high, it will cause muscle contraction, fibrillation of the heart, and tissue burns. The lack of
any visible sign that a conductor is electrified makes electricity a particular hazard. The pain caused by
an electric shock can be intense, leading electricity at times to be employed as a method of torture.
Death caused by an electric shock is referred to as electrocution. Electrocution is still the means of
judicial execution in some jurisdictions, though its use has become rarer in recent times.
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Electricity is not a human invention, and may be
observed in several forms in nature, a prominent manifestation of which is lightning. Many interactions
familiar at the macroscopic level, such as touch, friction or chemical bonding, are due to interactions
between electric fields on the atomic scale. The Earth's magnetic field is thought to arise from a natural
dynamo of circulating currents in the planet's core. Certain crystals, such as quartz, or even sugar,
generate a potential difference across their faces when subjected to external pressure. This
phenomenon is known as piezoelectricity, from the Greek piezein , meaning to press, and was
discovered in 1880 by Pierre and Jacques Curie. Paul-Jacques Curie (29 October 1855 – 19 February
1941) was a French physicist and professor of mineralogy at the University of Montpellier. Along with his
younger brother, Pierre Curie, he studied pyroelectricity in the 1880s, leading to their discovery of some
of the mechanisms behind piezoelectricity.The effect is reciprocal, and when a piezoelectric material is
subjected to an electric field, a small change in physical dimensions takes place.
In 1850, William Gladstone asked the scientist Michael
Faraday why electricity was valuable. Faraday answered, “One day sir, you may tax it.” William Ewart
Gladstone ( 29 December 1809 – 19 May 1898) was a British statesman and Liberal politician. In a career
lasting over 60 years, he served for 12 years as Prime Minister of the United Kingdom, spread over four
terms beginning in 1868 and ending in 1894. He also served as Chancellor of the Exchequer four times,
serving over 12 years.
This is a list of countries by electricity generation per year, based on multiple sources. China is the
world's largest electricity producing nation.
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Production and source ( 2011) :- Mega- means 1,000,000;. Giga- means 1,000,000,000; Tera- means
1,000,000,000,000; Peta- means 1,000,000,000,000,000 .
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Ten: 10 (1 zero) Hundred: 100 (2 zeros) Thousand: 1000 (3 zeros) Ten thousand 10,000 (4 zeros)
Hundred thousand 100,000 (5 zeros) Million 1,000,000 (6 zeros) Billion 1,000,000,000 (9 zeros ) Trillion
1,000,000,000,000 (12 zeros) Quadrillion 1,000,000,000,000,000 (15 zeros) Quintillion
1,000,000,000,000,000,000 (18 zeros) Sextillion 1,000,000,000,000,000,000,000 (21 zeros) Septillion
1,000,000,000,000,000,000,000,000 (24 zeros) Octillion 1,000,000,000,000,000,000,000,000,000 (27
zeros)
Nonillion
1,000,000,000,000,000,000,000,000,000,000
(30
zeros)
Decillion
1,000,000,000,000,000,000,000,000,000,000,000 (33 zeros)
India is the world's third largest producer and third
largest consumer of electricity.The national electric grid in India has an installed capacity of 374.2 GW as
of 31 December 2020. Renewable power plants, which also include large hydroelectric plants, constitute
36.17% of India's total installed capacity. During the 2019-20 fiscal year, the gross electricity generated
by utilities in India was 1,383.5 TWh and the total electricity generation (utilities and non utilities) in the
country was 1,598 TWh.The gross electricity consumption in 2019-20 was 1,208 kWh per capita. In
2015-16, electric energy consumption in agriculture was recorded as being the highest (17.89%)
worldwide. The per capita electricity consumption is low compared to most other countries despite
India having a low electricity tariff.
Electrical engineering is an engineering discipline
concerned with the study, design and application of equipment, devices and systems which use
electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the latter half
of the 19th century after commercialization of the electric telegraph, the telephone, and electrical
power generation, distribution and use.
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Electrical engineering is now divided into a wide range of fields,
including computer engineering, systems engineering, power engineering, telecommunications, radiofrequency engineering, signal processing, instrumentation, and electronics. Many of these disciplines
overlap with other engineering branches, spanning a huge number of specializations including hardware
engineering, power electronics, electromagnetics and waves, microwave engineering, nanotechnology,
electrochemistry, renewable energies, mechatronics, and electrical materials science.
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In the 19th century, research into the subject started to intensify.
Notable developments in this century include the work of Hans Christian Ørsted who discovered in 1820
that an electric current produces a magnetic field that will deflect a compass needle, of William
Sturgeon who, in 1825 invented the electromagnet, of Joseph Henry and Edward Davy who invented the
electrical relay in 1835, of Georg Ohm, who in 1827 quantified the relationship between the electric
current and potential difference in a conductor, of Michael Faraday (the discoverer of electromagnetic
induction in 1831), and of James Clerk Maxwell, who in 1873 published a unified theory of electricity and
magnetism in his treatise Electricity and Magnetism. Joseph Henry (December 17, 1797 – May 13, 1878)
was an American scientist who served as the first Secretary of the Smithsonian Institution. He was the
secretary for the National Institute for the Promotion of Science, a precursor of the Smithsonian
Institution. He was highly regarded during his lifetime. While building electromagnets, Henry discovered
the electromagnetic phenomenon of self-inductance. He also discovered mutual inductance
independently of Michael Faraday, though Faraday was the first to make the discovery and publish his
results. Henry developed the electromagnet into a practical device. He invented a precursor to the
electric doorbell (specifically a bell that could be rung at a distance via an electric wire, (1831)and
electric relay (1835). The SI unit of inductance, the Henry, is named in his honor. Henry's work on the
electromagnetic relay was the basis of the practical electrical telegraph, invented by Samuel F. B. Morse
and Sir Charles Wheatstone, separately. Edward Davy (16 June 1806 – 26 January 1885) was an English
physician, scientist, and inventor who played a prominent role in the development of telegraphy, and
invented an electric relay. Sir Charles Wheatstone (6 February 1802 – 19 October 1875), was an English
scientist and inventor of many scientific breakthroughs of the Victorian era, including the English
concertina, the stereoscope (a device for displaying three-dimensional images), and the Playfair cipher
(an encryption technique). However, Wheatstone is best known for his contributions in the
development of the Wheatstone bridge, originally invented by Samuel Hunter Christie, which is used to
measure an unknown electrical resistance, and as a major figure in the development of telegraphy.
Samuel Finley Breese Morse (April 27, 1791 – April 2, 1872) was an American inventor and painter. After
having established his reputation as a portrait painter, in his middle age Morse contributed to the
invention of a single-wire telegraph system based on European telegraphs. He was a co-developer of
Morse code and helped to develop the commercial use of telegraphy. Practical applications and
advances in such fields created an increasing need for standardised units of measure. They led to the
international standardization of the units volt, ampere, coulomb, ohm, farad, and henry. This was
achieved at an international conference in Chicago in 1893. The publication of these standards formed
the basis of future advances in standardisation in various industries, and in many countries, the
definitions were immediately recognized in relevant legislation.
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During these years, the study of electricity was largely
considered to be a subfield of physics since the early electrical technology was considered
electromechanical in nature. The Technische Universität Darmstadt founded the world's first
department of electrical engineering in 1882 and introduced the first degree course in electrical
engineering in 1883. The first electrical engineering degree program in the United States was started at
Massachusetts Institute of Technology (MIT) in the physics department under Professor Charles Cross,
though it was Cornell University to produce the world's first electrical engineering graduates in 1885.
The first course in electrical engineering was taught in 1883 in Cornell's Sibley College of Mechanical
Engineering and Mechanic Arts. It was not until about 1885 that Cornell President Andrew Dickson
White established the first Department of Electrical Engineering in the United States. In the same year,
University College London founded the first chair of electrical engineering in Great Britain. Professor
Mendell P. Weinbach at University of Missouri soon followed suit by establishing the electrical
engineering department in 1886. Afterwards, universities and institutes of technology gradually started
to offer electrical engineering programs to their students all over the world.
During these decades use of electrical engineering increased
dramatically. In 1882, Thomas Edison switched on the world's first large-scale electric power network
that provided 110 volts — direct current (DC) — to 59 customers on Manhattan Island in New York City.
In 1884, Sir Charles Parsons invented the steam turbine allowing for more efficient electric power
generation. Alternating current, with its ability to transmit power more efficiently over long distances
via the use of transformers, developed rapidly in the 1880s and 1890s with transformer designs by
Károly Zipernowsky, Ottó Bláthy and Miksa Déri (later called ZBD transformers), Lucien Gaulard, John
Dixon Gibbs and William Stanley, Jr.. Practical AC motor designs including induction motors were
independently invented by Galileo Ferraris and Nikola Tesla and further developed into a practical threephase form by Mikhail Dolivo-Dobrovolsky and Charles Eugene Lancelot Brown. Charles Steinmetz and
Oliver Heaviside contributed to the theoretical basis of alternating current engineering. The spread in
the use of AC set off in the United States what has been called the war of the currents between a
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George Westinghouse backed AC system and a Thomas Edison backed DC power system, with AC being
adopted as the overall standard. Charles Proteus Steinmetz (born Karl August Rudolph Steinmetz, April
9, 1865 – October 26, 1923) was a German-born American mathematician and electrical engineer and
professor at Union College. He fostered the development of alternating current that made possible the
expansion of the electric power industry in the United States, formulating mathematical theories for
engineers. He made ground-breaking discoveries in the understanding of hysteresis that enabled
engineers to design better electromagnetic apparatus equipment, especially electric motors for use in
industry. Oliver Heaviside ( 18 May 1850 – 3 February 1925) was an English autodidactic electrical
engineer, mathematician, and physicist who brought complex numbers to circuit analysis, invented a
new technique for solving differential equations (equivalent to the Laplace transform), independently
developed vector calculus, and rewrote Maxwell's equations in the form commonly used today. He
significantly shaped the way Maxwell's equations are understood and applied in the decades following
Maxwell's death. His formulation of the telegrapher's equations became commercially important during
his own lifetime, after their significance went unremarked for a long while, as few others were versed at
the time in his novel methodology. Although at odds with the scientific establishment for most of his
life, Heaviside changed the face of telecommunications, mathematics, and science.
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Practical applications and advances in such fields created an
increasing need for standardised units of measure. They led to the international standardization of the
units volt, ampere, coulomb, ohm, farad, and henry. This was achieved at an international conference in
Chicago in 1893. The publication of these standards formed the basis of future advances in
standardisation in various industries, and in many countries, the definitions were immediately
recognized in relevant legislation.
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Power engineering deals with the generation, transmission, and
distribution of electricity as well as the design of a range of related devices. These include transformers,
electric generators, electric motors, high voltage engineering, and power electronics. In many regions of
the world, governments maintain an electrical network called a power grid that connects a variety of
generators together with users of their energy. Users purchase electrical energy from the grid, avoiding
the costly exercise of having to generate their own. Power engineers may work on the design and
maintenance of the power grid as well as the power systems that connect to it. Such systems are called
on-grid power systems and may supply the grid with additional power, draw power from the grid, or do
both. Power engineers may also work on systems that do not connect to the grid, called off-grid power
systems, which in some cases are preferable to on-grid systems. The future includes Satellite controlled
power systems, with feedback in real time to prevent power surges and prevent blackouts. Control engg
focuses on the modeling of a diverse range of dynamic systems and the design of controllers that will
cause these systems to behave in the desired manner. To implement such controllers, electrical
engineers may use electronic circuits, digital signal processors, microcontrollers, and programmable
logic controllers (PLCs). Control engineering has a wide range of applications from the flight and
propulsion systems of commercial airliners to the cruise control present in many modern automobiles. It
also plays an important role in industrial automation.
Control engineers often utilize feedback when designing control
systems. For example, in an automobile with cruise control the vehicle's speed is continuously
monitored and fed back to the system which adjusts the motor's power output accordingly. Where
there is regular feedback, control theory can be used to determine how the system responds to such
feedback.
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Electrical engineers also work in robotics to design autonomous
systems using control algorithms which interpret sensory feedback to control actuators that move
robots such as autonomous vehicles, autonomous drones and others used in a variety of industries.
Electronic engineering involves the design and testing of electronic circuits that use the properties of
components such as resistors, capacitors, inductors, diodes, and transistors to achieve a particular
functionality. The tuned circuit, which allows the user of a radio to filter out all but a single station, is
just one example of such a circuit. Another example to research is a pneumatic signal conditioner.
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Prior to the Second World War, the subject was commonly
known as radio engineering and basically was restricted to aspects of communications and radar,
commercial radio, and early television. Later, in post-war years, as consumer devices began to be
developed, the field grew to include modern television, audio systems, computers, and microprocessors.
In the mid-to-late 1950s, the term radio engineering gradually gave way to the name electronic
engineering.
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Before the invention of the integrated circuit in 1959,
electronic circuits were constructed from discrete components that could be manipulated by humans.
These discrete circuits consumed much space and power and were limited in speed, although they are
still common in some applications. By contrast, integrated circuits packed a large number—often
millions—of tiny electrical components, mainly transistors, into a small chip around the size of a coin.
This allowed for the powerful computers and other electronic devices we see today. Micro electronics
engineering deals with the design and microfabrication of very small electronic circuit components for
use in an integrated circuit or sometimes for use on their own as a general electronic component. The
most common microelectronic components are semiconductor transistors, although all main electronic
components (resistors, capacitors etc.) can be created at a microscopic level.
Nanoelectronics is the further scaling of devices down to
nanometer levels. Modern devices are already in the nanometer regime, with below 100 nm processing
having been standard since around 2002.
Microelectronic components are created by chemically
fabricating wafers of semiconductors such as silicon (at higher frequencies, compound semiconductors
like gallium arsenide and indium phosphide) to obtain the desired transport of electronic charge and
control of current. The field of microelectronics involves a significant amount of chemistry and material
science and requires the electronic engineer working in the field to have a very good working knowledge
of the effects of quantum mechanics.
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Signal processing deals with the analysis and manipulation
of signals. Signals can be either analog, in which case the signal varies continuously according to the
information, or digital, in which case the signal varies according to a series of discrete values
representing the information. For analog signals, signal processing may involve the amplification and
filtering of audio signals for audio equipment or the modulation and demodulation of signals for
telecommunications. For digital signals, signal processing may involve the compression, error detection
and error correction of digitally sampled signals.
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Signal Processing is a very mathematically oriented
and intensive area forming the core of digital signal processing and it is rapidly expanding with new
applications in every field of electrical engineering such as communications, control, radar, audio
engineering, broadcast engineering, power electronics, and biomedical engineering as many already
existing analog systems are replaced with their digital counterparts. Analog signal processing is still
important in the design of many control systems.
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DSP processor ICs are found in many types of modern electronic
devices, such as digital television sets, radios, Hi-Fi audio equipment, mobile phones, multimedia
players, camcorders and digital cameras, automobile control systems, noise cancelling headphones,
digital spectrum analyzers, missile guidance systems, radar systems, and telematics systems. In such
products, DSP may be responsible for noise reduction, speech recognition or synthesis, encoding or
decoding digital media, wirelessly transmitting or receiving data, triangulating position using GPS, and
other kinds of image processing, video processing, audio processing, and speech processing.
Tele communication engg focuses on the transmission of
information across a communication channel such as a coax cable, optical fiber or free space.
Transmissions across free space require information to be encoded in a carrier signal to shift the
information to a carrier frequency suitable for transmission; this is known as modulation. Popular analog
modulation techniques include amplitude modulation and frequency modulation. The choice of
modulation affects the cost and performance of a system and these two factors must be balanced
carefully by the engineer.
Once the transmission characteristics of a system are
determined, telecommunication engineers design the transmitters and receivers needed for such
systems. These two are sometimes combined to form a two-way communication device known as a
transceiver. A key consideration in the design of transmitters is their power consumption as this is
closely related to their signal strength.Typically, if the power of the transmitted signal is insufficient
once the signal arrives at the receiver's antenna(s), the information contained in the signal will be
corrupted by noise.
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Instrumentation engg deals with the design of devices to
measure physical quantities such as pressure, flow, and temperature. The design of such instruments
requires a good understanding of physics that often extends beyond electromagnetic theory. For
example, flight instruments measure variables such as wind speed and altitude to enable pilots the
control of aircraft analytically. Similarly, thermocouples use the Peltier-Seebeck effect to measure the
temperature difference between two points.
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Often instrumentation is not used by itself, but instead as the sensors of larger electrical systems. For
example, a thermocouple might be used to help ensure a furnace's temperature remains constant. For
this reason, instrumentation engineering is often viewed as the counterpart of control.
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Computer engineering deals with the design of computers and computer systems. This may involve the
design of new hardware, the design of PDAs, tablets, and supercomputers, or the use of computers to
control an industrial plant. Computer engineers may also work on a system's software. However, the
design of complex software systems is often the domain of software engineering, which is usually
considered a separate discipline. Desktop computers represent a tiny fraction of the devices a computer
engineer might work on, as computer-like architectures are now found in a range of devices including
video game consoles and DVD players.
Mechatronics is an engineering discipline which deals with the
convergence of electrical and mechanical systems. Such combined systems are known as
electromechanical systems and have widespread adoption. Examples include automated manufacturing
systems, heating, ventilation and air-conditioning systems, and various subsystems of aircraft and
automobiles. Electronic systems design is the subject within electrical engineering that deals with the
multi-disciplinary design issues of complex electrical and mechanical systems.
The term mechatronics is typically used to refer to macroscopic
systems but futurists have predicted the emergence of very small electromechanical devices. Already,
such small devices, known as Microelectromechanical systems (MEMS), are used in automobiles to tell
airbags when to deploy, in digital projectors to create sharper images, and in inkjet printers to create
nozzles for high definition printing. In the future it is hoped the devices will help build tiny implantable
medical devices and improve optical communication.
Biomedical engineering is another related discipline, concerned
with the design of medical equipment. This includes fixed equipment such as ventilators, MRI scanners,
and electrocardiograph monitors as well as mobile equipment such as cochlear implants, artificial
pacemakers, and artificial hearts.
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Aerospace engineering and robotics an example is the most recent
electric propulsion and ion propulsion.
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A measuring instrument is a device to measure a
physical quantity. In the physical sciences, quality assurance, and engineering, measurement is the
activity of obtaining and comparing physical quantities of real-world objects and events. Established
standard objects and events are used as units, and the process of measurement gives a number relating
the item under study and the referenced unit of measurement. Measuring instruments, and formal test
methods which define the instrument's use, are the means by which these relations of numbers are
obtained. All measuring instruments are subject to varying degrees of instrument error and
measurement uncertainty. These instruments may range from simple objects such as rulers and
stopwatches to electron microscopes and particle accelerators. Virtual instrumentation is widely used in
the development of modern measuring instruments.
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List of electrical and electronic measuring instruments :-
An oscilloscope, previously called an oscillograph, and
informally known as a scope or o-scope, CRO (for cathode-ray oscilloscope), or DSO (for the more
modern digital storage oscilloscope), is a type of electronic test instrument that graphically displays
varying signal voltages, usually as a calibrated two-dimensional plot of one or more signals as a function
of time. The displayed waveform can then be analyzed for properties such as amplitude, frequency, rise
time, time interval, distortion, and others. Originally, calculation of these values required manually
measuring the waveform against the scales built into the screen of the instrument. Modern digital
instruments may calculate and display these properties directly.
The oscilloscope can be adjusted so that repetitive signals can be observed
as a persistent waveform on the screen. A storage oscilloscope can capture a single event and display it
continuously, so the user can observe events that would otherwise appear too briefly to see directly.
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An electric light is a device that produces visible light from
electric current. It is the most common form of artificial lighting and is essential to modern society,
providing interior lighting for buildings and exterior light for evening and nighttime activities. In
technical usage, a replaceable component that produces light from electricity is called a lamp. Lamps are
commonly called light bulbs; for example, the incandescent light bulb. Lamps usually have a base made
of ceramic, metal, glass, or plastic, which secures the lamp in the socket of a light fixture. The electrical
connection to the socket may be made with a screw-thread base, two metal pins, two metal caps or a
bayonet cap.
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The three main categories of electric lights are incandescent lamps, which produce light by a filament
heated white-hot by electric current, gas-discharge lamps, which produce light by means of an electric
arc through a gas, and LED lamps, which produce light by a flow of electrons across a band gap in a
semiconductor.
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Before electric lighting became common in the early 20th
century, people used candles, gas lights, oil lamps, and fires. English chemist Humphry Davy developed
the first incandescent light in 1802, followed by the first practical electric arc light in 1806. By the 1870s,
Davy's arc lamp had been successfully commercialized, and was used to light many public spaces. Efforts
by Joseph Swan and Thomas Edison led to commercial incandescent light bulbs becoming widely
available in the 1880s, and by the early twentieth century these had completely replaced arc lamps.
Types of electric lighting include:
Incandescent light bulb, a heated filament inside a glass envelope
Halogen lamps are incandescent lamps that use a fused quartz envelope filled with halogen gas
LED lamp, a solid-state lamp that uses light-emitting diodes (LEDs) as the source of light
Arc lamp
Xenon arc lamp
Mercury-xenon arc lamp
Ultra-high-performance lamp, an ultra-high-pressure mercury-vapor arc lamp for use in movie
projectors
Metal-halide lamp
Gas-discharge lamp, a light source that generates light by sending an electric discharge through an
ionized gas
Fluorescent lamp
Compact fluorescent lamp, a fluorescent lamp designed to replace an incandescent lamp
Neon lamp
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Mercury-vapor lamp
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Sodium-vapor lamp
Sulfur lamp
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Electrodeless lamp, a gas discharge lamp in which the power is transferred from outside the bulb to
inside via electromagnetic fields
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With the discovery of fire, the earliest form of artificial lighting
used to illuminate an area were campfires or torches. As early as 400,000 BCE, fire was kindled in the
caves of Peking Man. Prehistoric people used primitive oil lamps to illuminate surroundings. These
lamps were made from naturally occurring materials such as rocks, shells, horns and stones, were filled
with grease, and had a fiber wick. Lamps typically used animal or vegetable fats as fuel. Hundreds of
these lamps (hollow worked stones) have been found in the Lascaux caves in modern-day France, dating
to about 15,000 years ago. Oily animals (birds and fish) were also used as lamps after being threaded
with a wick. Fireflies have been used as lighting sources. Candles and glass and pottery lamps were also
invented. Chandeliers were an early form of "light fixture".A major reduction in the cost of lighting
occurred with the discovery of whale oil. The use of whale oil declined after Abraham Gesner, a
Canadian geologist, first refined kerosene in the 1840s, allowing brighter light to be produced at
substantially lower cost. In the 1850s, the price of whale oil dramatically increased (more than doubling
from 1848 to 1856) due to shortages of available whales, hastening whale oil's decline. By 1860, there
were 33 kerosene plants in the United States, and Americans spent more on gas and kerosene than on
whale oil. The final death knell for whale oil was in 1859, when crude oil was discovered and the
petroleum industry arose.
Gas lighting was economical enough to power street lights in
major cities starting in the early 1800s, and was also used in some commercial buildings and in the
homes of wealthy people. The gas mantle boosted the luminosity of utility lighting and of kerosene
lanterns. The next major drop in price came about in the 1880s with the introduction of electric lighting
in the form of arc lights for large space and street lighting followed on by incandescent light bulb based
utilities for indoor and outdoor lighting.
Over time, electric lighting became ubiquitous in developed countries.
Segmented sleep patterns disappeared, improved nighttime lighting made more activities possible at
night, and more street lights reduced urban crime.
Street lights are used to light roadways and walkways at night.
Some manufacturers are designing LED and photovoltaic luminaires to provide an energy-efficient
alternative to traditional street light fixtures. Floodlights are used to illuminate outdoor playing fields or
work zones during nighttime.
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Floodlights can be used to illuminate work zones or outdoor playing
fields during nighttime hours. The most common type of floodlights are metal halide and high pressure
sodium lights.
Beacon lights are positioned at the intersection of two roads to aid in navigation.
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Sometimes security lighting can be used along roadways in urban
areas, or behind homes or commercial facilities. These are extremely bright lights used to deter crime.
Security lights may include floodlights and be activated with PIR switches that detect moving heat
sources in darkness.
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Entry lights can be used outside to illuminate and signal the entrance
to a property. These lights are installed for safety, security, and for decoration.
A major appliance, or domestic appliance, is a large machine
in home appliance used for routine housekeeping tasks such as cooking, washing laundry, or food
preservation. An appliance is different from a plumbing fixture because it uses electricity or fuel.
Major appliances may be roughly divided as follows:
Refrigeration equipment
Freezer
Refrigerator
Water cooler
Cooking
Kitchen stove, also known as a range, cooker, oven, cooking plate, or cooktop
Microwave oven
Washing and drying equipment
Washing machine
Clothes dryer
Drying cabinet
Dishwasher
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Heating and cooling
Air conditioner
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Water heater
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A small appliance, small domestic appliance, or small electrics are
portable or semi-portable machines, generally used on table-tops, counter-tops, or other platforms, to
accomplish a household task. Examples include microwave ovens, toasters, humidifiers, food processors
and coffeemakers. They contrast with major appliances (British "white goods"), such as the refrigerator
and washing machine, which cannot be easily moved and are generally placed on the floor. Small
appliances also contrast with consumer electronics (British "brown goods") which are for leisure and
entertainment rather than purely practical tasks.
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Small appliances include those used for :
Beverage-making, such as electric kettles, coffeemakers or iced tea-makers
Cleaning, such as Vacuum cleaner
Cooking, such as on a hot plate or with a microwave oven
Lighting, using light fixtures
Thermal comfort, such as an electric heater or fan
Many small appliances perform a combination of the above processes such as mixing, heating by a
bread machine
Consumer electronics or home electronics are electronic (analog or digital) equipment intended for
everyday use, typically in private homes. Consumer electronics include devices used for entertainment,
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communications and recreation. Usually referred to as black goods due to many products being housed
in black or dark casings. This term is used to distinguish them from "white goods" which are meant for
housekeeping tasks, such as washing machines and refrigerators, although nowadays, these would be
considered brown goods, some of these being connected to the Internet. In British English, they are
often called brown goods by producers and sellers. In the 2010s, this distinction is absent in large big
box consumer electronics stores, which sell both entertainment, communication, and home office
devices and kitchen appliances such as refrigerators. Radio broadcasting in the early 20th century
brought the first major consumer product, the broadcast receiver. Later products included telephones,
televisions, and calculators, then audio and video recorders and players, game consoles, personal
computers and MP3 players. In the 2010s, consumer electronics stores often sell GPS, automotive
electronics (car stereos), video game consoles, electronic musical instruments (e.g., synthesizer
keyboards), karaoke machines, digital cameras, and video players (VCRs in the 1980s and 1990s,
followed by DVD players and Blu-ray players). Stores also sell smart appliances, digital cameras,
camcorders, cell phones, and smartphones. Some of the newer products sold include virtual reality
head-mounted display goggles, smart home devices that connect home devices to the Internet and
wearable technology.
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Information technology (IT) is the use of computers to
store, retrieve, transmit, and manipulate data[1] or information. IT is typically used within the context of
business operations as opposed to personal or entertainment technologies. IT is considered to be a
subset of information and communications technology (ICT). An information technology system (IT
system) is generally an information system, a communications system, or, more specifically speaking, a
computer system – including all hardware, software, and peripheral equipment – operated by a limited
group of users.
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Consumer electronics devices include those used for
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entertainment (flatscreen TVs, television sets, MP3 players, video recorders, DVD players, radio
receivers, etc.)
communications (telephones, cell phones, e-mail-capable personal computers, desktop computers,
laptops, printers, paper shredders, etc.)
recreation (digital cameras, camcorders, video game consoles, ROM cartridges, remote control cars,
Robot kits, etc.).
An electric generator is a device that converts mechanical energy to electrical energy. A generator forces
electrons to flow through an external electrical circuit. It is somewhat analogous to a water pump, which
creates a flow of water but does not create the water inside. The source of mechanical energy, the
prime mover, may be a reciprocating or turbine steam engine, water falling through a turbine or
waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air or any other
source of mechanical energy.
An AC generator converts mechanical energy into alternating
current electricity. Because power transferred into the field circuit is much less than power transferred
into the armature circuit, AC generators nearly always have the field winding on the rotor and the
armature winding on the stator.
AC generators are classified into several types.
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In an induction generator, the stator magnetic flux induces currents in
the rotor. The prime mover then drives the rotor above the synchronous speed, causing the opposing
rotor flux to cut the stater coils producing active current in the stater coils, thus sending power back to
the electrical grid. An induction generator draws reactive power from the connected system and so
cannot be an isolated source of power.
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In a Synchronous generator (alternator), the current for the
magnetic field is provided by a separate DC current source.
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A DC generator is a machine that converts mechanical energy into
Direct Current electrical energy. A DC generator generally has a commutator with split ring to produce a
direct current instead of an alternating current.
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An AC motor converts alternating current into mechanical energy.
It commonly consists of two basic parts, an outside stationary stator having coils supplied with
alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft
that is given a torque by the rotating field. The two main types of AC motors are distinguished by the
type of rotor used.
Induction (asynchronous) motor, the rotor magnetic field is
created by an induced current. The rotor must turn slightly slower (or faster) than the stator magnetic
field to provide the induced current. There are three types of induction motor rotors, which are squirrelcage rotor, wound rotor and solid core rotor.
Synchronous motor, it does not rely on induction and so can
rotate exactly at the supply frequency or sub-multiple. The magnetic field of the rotor is either
generated by direct current delivered through slip rings (exciter) or by a permanent magnet.
The brushed DC electric motor generates torque directly
from DC power supplied to the motor by using internal commutation, stationary permanent magnets,
and rotating electrical magnets. Brushes and springs carry the electric current from the commutator to
the spinning wire windings of the rotor inside the motor. Brushless DC motors use a rotating permanent
magnet in the rotor, and stationary electrical magnets on the motor housing. A motor controller
converts DC to AC. This design is simpler than that of brushed motors because it eliminates the
complication of transferring power from outside the motor to the spinning rotor. An example of a
brushless, synchronous DC motor is a stepper motor which can divide a full rotation into a large number
of steps.
Other electromagnetic machines include the Amplidyne,
Synchro, Metadyne, Eddy current clutch, Eddy current brake, Eddy current dynamometer, Hysteresis
dynamometer, Rotary converter, and Ward Leonard set. A rotary converter is a combination of
machines that act as a mechanical rectifier, inverter or frequency converter. The Ward Leonard set is a
combination of machines used to provide speed control. Other machine combinations include the
Kraemer and Scherbius systems.
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A transformer is a static device that converts alternating
current from one voltage level to another level (higher or lower), or to the same level, without changing
the frequency. A transformer transfers electrical energy from one circuit to another through inductively
coupled conductors—the transformer's coils. A varying electric current in the first or primary winding
creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the
secondary winding. This varying magnetic field induces a varying electromotive force (emf) or "voltage"
in the secondary winding. This effect is called mutual induction.
Step-up transformer
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There are three types of transformers
Step-down transformer
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Isolation transformer
There are four types of transformers based on structure
core type
shell type
power type
instrument type
PM machines have permanent magnets in the rotor
which set up a magnetic field. The magnetomotive force in a PM (caused by orbiting electrons with
aligned spin) is generally much higher than what is possible in a copper coil. The copper coil can,
however, be filled with a ferromagnetic material, which gives the coil much lower magnetic reluctance.
Still the magnetic field created by modern PMs (Neodymium magnets) is stronger, which means that PM
machines have a better torque/volume and torque/weight ratio than machines with rotor coils under
continuous operation. This may change with introduction of superconductors in rotor.
Brushed machines are machines where the rotor coil is
supplied with current through brushes in much the same way as current is supplied to the car in an
electric slot car track. More durable brushes can be made of graphite or liquid metal. It is even possible
to eliminate the brushes in a "brushed machine" by using a part of rotor and stator as a transformer
which transfer current without creating torque. Brushes must not be confused with a commutator. The
difference is that the brushes only transfer electric current to a moving rotor while a commutator also
provide switching of the current direction.
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Induction machines have short circuited rotor coils where a
current is set up and maintained by induction. This requires that the rotor rotates at other than
synchronous speed, so that the rotor coils are subjected to a varying magnetic field created by the stator
coils. An induction machine is an asynchronous machine.
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Induction eliminates the need for brushes which is usually
a weak part in an electric machine. It also allows designs which make it very easy to manufacture the
rotor. A metal cylinder will work as rotor, but to improve efficiency a "squirrel cage" rotor or a rotor with
closed windings is usually used. The speed of asynchronous induction machines will decrease with
increased load because a larger speed difference between stator and rotor is necessary to set up
sufficient rotor current and rotor magnetic field. Asynchronous induction machines can be made so they
start and run without any means of control if connected to an AC grid, but the starting torque is low.
A special case would be an induction machine with
superconductors in the rotor. The current in the superconductors will be set up by induction, but the
rotor will run at synchronous speed because there will be no need for a speed difference between the
magnetic field in stator and speed of rotor to maintain the rotor current.
Another special case would be the brushless double fed induction
machine, which has a double set of coils in the stator. Since it has two moving magnetic fields in the
stator, it gives no meaning to talk about synchronous or asynchronous speed.
Reluctance machines have no windings on the rotor,
only a ferromagnetic material shaped so that "electromagnets" in stator can "grab" the teeth in rotor
and advance it a little. The electromagnets are then turned off, while another set of electromagnets is
turned on to move rotor further. Another name is step motor, and it is suited for low speed and
accurate position control. Reluctance machines can be supplied with permanent magnets in the stator
to improve performance. The “electromagnet” is then “turned off” by sending a negative current in the
coil. When the current is positive the magnet and the current cooperate to create a stronger magnetic
field which will improve the reluctance machine's maximum torque without increasing the currents
maximum absolute value.
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Electro static generator generate electricity by building up
electric charge. Early types were friction machines, later ones were influence machines that worked by
electrostatic induction. The Van de Graaff generator is an electrostatic generator still used in research
today.
For optimized or practical operation of electric machines, today's
electric machine systems are complemented with electronic control
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A fan is a powered machine used to create a flow of air. A fan consists
of a rotating arrangement of vanes or blades, which act on the air. The rotating assembly of blades and
hub is known as an impeller, rotor, or runner. Usually, it is contained within some form of housing, or
case. This may direct the airflow, or increase safety by preventing objects from contacting the fan
blades. Most fans are powered by electric motors, but other sources of power may be used, including
hydraulic motors, handcranks, and internal combustion engines.
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The punkah fan was used in India about 500 BCE. It was a handheld fan
made from bamboo strips or other plant fiber, that could be rotated or fanned to move air. During
British rule, the word came to be used by Anglo-Indians to mean a large swinging flat fan, fixed to the
ceiling and pulled by a servant called the punkawallah.
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Between 1882 and 1886 Schuyler Wheeler invented a fan powered by
electricity. It was commercially marketed by the American firm Crocker & Curtis electric motor company.
In 1882, Philip Diehl developed the world's first electric ceiling fan. During this intense period of
innovation, fans powered by alcohol, oil, or kerosene were common around the turn of the 20th
century. In 1909, KDK of Japan pioneered the invention of mass-produced electric fans for home use. In
the 1920s, industrial advances allowed steel fans to be mass-produced in different shapes, bringing fan
prices down and allowing more homeowners to afford them. In the 1930s, the first art deco fan (the
"Silver Swan") was designed by Emerson. By the 1940s, Crompton Greaves of India became the world's
largest manufacturer of electric ceiling fans mainly for sale in India, Asia, and the Middle East. By the
1950s, table and stand fans were manufactured in bright colors and eye-catching.
An electric power system is a network of electrical
components deployed to supply, transfer, and use electric power. An example of a power system is the
electrical grid that provides power to homes and industry within an extended area. The electrical grid
can be broadly divided into the generators that supply the power, the transmission system that carries
the power from the generating centers to the load centers, and the distribution system that feeds the
power to nearby homes and industries. Smaller power systems are also found in industry, hospitals,
commercial buildings and homes. The majority of these systems rely upon three-phase AC power—the
standard for large-scale power transmission and distribution across the modern world. Specialized
power systems that do not always rely upon three-phase AC power are found in aircraft, electric rail
systems, ocean liners, submarines and automobiles.
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In 1881, two electricians built the world's first power system at
Godalming in England. It was powered by two waterwheels and produced an alternating current that in
turn supplied seven Siemens arc lamps at 250 volts and 34 incandescent lamps at 40 volts. However,
supply to the lamps was intermittent and in 1882 Thomas Edison and his company, The Edison Electric
Light Company, developed the first steam-powered electric power station on Pearl Street in New York
City. The Pearl Street Station initially powered around 3,000 lamps for 59 customers. The power station
generated direct current and operated at a single voltage. Direct current power could not be
transformed easily or efficiently to the higher voltages necessary to minimize power loss during longdistance transmission, so the maximum economic distance between the generators and load was
limited to around half a mile (800 m).
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That same year in London, Lucien Gaulard and John Dixon Gibbs
demonstrated the "secondary generator"—the first transformer suitable for use in a real power system.
The practical value of Gaulard and Gibbs' transformer was demonstrated in 1884 at Turin where the
transformer was used to light up forty kilometres (25 miles) of railway from a single alternating current
generator. Despite the success of the system, the pair made some fundamental mistakes. Perhaps the
most serious was connecting the primaries of the transformers in series so that active lamps would
affect the brightness of other lamps further down the line.
In 1885, Ottó Titusz Bláthy working with Károly Zipernowsky
and Miksa Déri perfected the secondary generator of Gaulard and Gibbs, providing it with a closed iron
core and its present name: the "transformer". The three engineers went on to present a power system
at the National General Exhibition of Budapest that implemented the parallel AC distribution system
proposed by a British scientist[a] in which several power transformers have their primary windings fed in
parallel from a high-voltage distribution line. The system lit more than 1000 carbon filament lamps and
operated successfully from May until November of that year.
Also in 1885 George Westinghouse, an American
entrepreneur, obtained the patent rights to the Gaulard-Gibbs transformer and imported a number of
them along with a Siemens generator, and set his engineers to experimenting with them in hopes of
improving them for use in a commercial power system. In 1886, one of Westinghouse's engineers,
William Stanley, independently recognized the problem with connecting transformers in series as
opposed to parallel and also realized that making the iron core of a transformer a fully enclosed loop
would improve the voltage regulation of the secondary winding. Using this knowledge he built a multivoltage transformer-based alternating-current power system serving multiple homes and businesses at
Great Barrington, Massachusetts in 1886. The system was unreliable though (due primarily to
generation issues) and short-lived. However based on that system Westinghouse would begin installing
AC transformer systems in competition with the Edison company later that year. In 1888, Westinghouse
licensed Nikola Tesla's patents for a polyphase AC induction motor and transformer designs. Tesla
consulted for a year at the Westinghouse Electric & Manufacturing Company's but it took a further four
years for Westinghouse engineers to develop a workable polyphase motor and transmission system.
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By 1889, the electric power industry was flourishing,
and power companies had built thousands of power systems (both direct and alternating current) in the
United States and Europe. These networks were effectively dedicated to providing electric lighting.
During this time the rivalry between Thomas Edison and George Westinghouse's companies had grown
into a propaganda campaign over which form of transmission (direct or alternating current) was
superior, a series of events known as the "war of the currents". In 1891, Westinghouse installed the first
major power system that was designed to drive a 100 horsepower (75 kW) synchronous electric motor,
not just provide electric lighting, at Telluride, Colorado. On the other side of the Atlantic, Mikhail DolivoDobrovolsky and Charles Eugene Lancelot Brown, built the first long-distance (175 km) high-voltage (15
kV, then a record) three-phase transmission line from Lauffen am Neckar to Frankfurt am Main for the
Electrical Engineering Exhibition in Frankfurt, where power was used to light lamps and run a water
pump. In the United States the AC/DC competition came to an end when Edison General Electric was
taken over by their chief AC rival, the Thomson-Houston Electric Company, forming General Electric. In
1895, after a protracted decision-making process, alternating current was chosen as the transmission
standard with Westinghouse building the Adams No. 1 generating station at Niagara Falls and General
Electric building the three-phase alternating current power system to supply Buffalo at 11 kV.
Developments in power systems continued beyond the
nineteenth century. In 1936 the first experimental high voltage direct current (HVDC) line using mercury
arc valves was built between Schenectady and Mechanicville, New York. HVDC had previously been
achieved by series-connected direct current generators and motors (the Thury system) although this
suffered from serious reliability issues. The first solid-state metal diode suitable for general power uses
was developed by Ernst Presser at TeKaDe in 1928. It consisted of a layer of selenium applied on an
aluminum plate. In 1957, a General Electric research group developed the first thyristor suitable for use
in power applications, starting a revolution in power electronics. In that same year, Siemens
demonstrated a solid-state rectifier, but it was not until the early 1970s that solid-state devices became
the standard in HVDC, when GE emerged as one of the top suppliers of thyristor-based HVDC. In 1979, a
European consortium including Siemens, Brown Boveri & Cie and AEG realized the record HVDC link
from Cabora Bassa to Johannesburg, extending more than 1,420 km that carried 1.9 GW at 533 kV.
In recent times, many important developments have
come from extending innovations in the information and communications technology (ICT) field to the
power engineering field. For example, the development of computers meant load flow studies could be
run more efficiently allowing for much better planning of power systems. Advances in information
technology and telecommunication also allowed for effective remote control of a power system's
switchgear and generators.
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All power systems have one or more sources of power. For some
power systems, the source of power is external to the system but for others, it is part of the system
itself—it is these internal power sources that are discussed in the remainder of this section. Direct
current power can be supplied by batteries, fuel cells or photovoltaic cells. Alternating current power is
typically supplied by a rotor that spins in a magnetic field in a device known as a turbo generator. There
have been a wide range of techniques used to spin a turbine's rotor, from steam heated using fossil fuel
(including coal, gas and oil) or nuclear energy to falling water (hydroelectric power) and wind (wind
power).
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The speed at which the rotor spins in combination with the
number of generator poles determines the frequency of the alternating current produced by the
generator. All generators on a single synchronous system, for example, the national grid, rotate at submultiples of the same speed and so generate electric current at the same frequency. If the load on the
system increases, the generators will require more torque to spin at that speed and, in a steam power
station, more steam must be supplied to the turbines driving them. Thus the steam used and the fuel
expended directly relate to the quantity of electrical energy supplied. An exception exists for generators
incorporating power electronics such as gearless wind turbines or linked to a grid through an
asynchronous tie such as a HVDC link — these can operate at frequencies independent of the power
system frequency.
Depending on how the poles are fed, alternating current generators
can produce a variable number of phases of power. A higher number of phases leads to more efficient
power system operation but also increases the infrastructure requirements of the system. Electricity
grid systems connect multiple generators operating at the same frequency: the most common being
three-phase at 50 or 60 Hz.
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There are a range of design considerations for power
supplies. These range from the obvious: How much power should the generator be able to supply? What
is an acceptable length of time for starting the generator (some generators can take hours to start)? Is
the availability of the power source acceptable (some renewables are only available when the sun is
shining or the wind is blowing)? To the more technical: How should the generator start (some turbines
act like a motor to bring themselves up to speed in which case they need an appropriate starting
circuit)? What is the mechanical speed of operation for the turbine and consequently what are the
number of poles required? What type of generator is suitable (synchronous or asynchronous) and what
type of rotor (squirrel-cage rotor, wound rotor, salient pole rotor or cylindrical rotor)?
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A toaster is a great example of a single-phase load that might
appear in a residence. Toasters typically draw 2 to 10 amps at 110 to 260 volts consuming around 600 to
1200 watts of power.
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Power systems deliver energy to loads that perform a
function. These loads range from household appliances to industrial machinery. Most loads expect a
certain voltage and, for alternating current devices, a certain frequency and number of phases. The
appliances found in residential settings, for example, will typically be single-phase operating at 50 or 60
Hz with a voltage between 110 and 260 volts (depending on national standards). An exception exists for
larger centralized air conditioning systems as in some countries these are now typically three-phase
because this allows them to operate more efficiently. All electrical appliances also have a wattage rating,
which specifies the amount of power the device consumes. At any one time, the net amount of power
consumed by the loads on a power system must equal the net amount of power produced by the
supplies less the power lost in transmission.
Making sure that the voltage, frequency and
amount of power supplied to the loads is in line with expectations is one of the great challenges of
power system engineering. However it is not the only challenge, in addition to the power used by a load
to do useful work (termed real power) many alternating current devices also use an additional amount
of power because they cause the alternating voltage and alternating current to become slightly out-ofsync (termed reactive power). The reactive power like the real power must balance (that is the reactive
power produced on a system must equal the reactive power consumed) and can be supplied from the
generators, however it is often more economical to supply such power from capacitors (see "Capacitors
and reactors" below for more details).
A final consideration with loads has to do with power
quality. In addition to sustained overvoltages and undervoltages (voltage regulation issues) as well as
sustained deviations from the system frequency (frequency regulation issues), power system loads can
be adversely affected by a range of temporal issues. These include voltage sags, dips and swells,
transient overvoltages, flicker, high-frequency noise, phase imbalance and poor power factor. Power
quality issues occur when the power supply to a load deviates from the ideal. Power quality issues can
be especially important when it comes to specialist industrial machinery or hospital equipment.
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Conductors carry power from the generators to the load. In a grid,
conductors may be classified as belonging to the transmission system, which carries large amounts of
power at high voltages (typically more than 69 kV) from the generating centres to the load centres, or
the distribution system, which feeds smaller amounts of power at lower voltages (typically less than 69
kV) from the load centres to nearby homes and industry.
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Choice of conductors is based on considerations such as cost,
transmission losses and other desirable characteristics of the metal like tensile strength. Copper, with
lower resistivity than aluminum, was once the conductor of choice for most power systems. However,
aluminum has a lower cost for the same current carrying capacity and is now often the conductor of
choice. Overhead line conductors may be reinforced with steel or aluminium alloys.[31]
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Conductors in exterior power systems may be placed overhead or underground. Overhead conductors
are usually air insulated and supported on porcelain, glass or polymer insulators. Cables used for
underground transmission or building wiring are insulated with cross-linked polyethylene or other
flexible insulation. Conductors are often stranded for to make them more flexible and therefore easier
to install.
Conductors are typically rated for the maximum current that they
can carry at a given temperature rise over ambient conditions. As current flow increases through a
conductor it heats up. For insulated conductors, the rating is determined by the insulation. For bare
conductors, the rating is determined by the point at which the sag of the conductors would become
unacceptable.
The majority of the load in a typical AC power system is
inductive; the current lags behind the voltage. Since the voltage and current are out-of-phase, this leads
to the emergence of an "imaginary" form of power known as reactive power. Reactive power does no
measurable work but is transmitted back and forth between the reactive power source and load every
cycle. This reactive power can be provided by the generators themselves but it is often cheaper to
provide it through capacitors, hence capacitors are often placed near inductive loads (i.e. if not on-site
at the nearest substation) to reduce current demand on the power system (i.e. increase the power
factor).
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Reactors consume reactive power and are used to regulate
voltage on long transmission lines. In light load conditions, where the loading on transmission lines is
well below the surge impedance loading, the efficiency of the power system may actually be improved
by switching in reactors. Reactors installed in series in a power system also limit rushes of current flow,
small reactors are therefore almost always installed in series with capacitors to limit the current rush
associated with switching in a capacitor. Series reactors can also be used to limit fault currents.
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Capacitors and reactors are switched by circuit breakers,
which results in moderately large step changes of reactive power. A solution to this comes in the form of
synchronous condensers, static VAR compensators and static synchronous compensators. Briefly,
synchronous condensers are synchronous motors that spin freely to generate or absorb reactive power.
Static VAR compensators work by switching in capacitors using thyristors as opposed to circuit breakers
allowing capacitors to be switched-in and switched-out within a single cycle. This provides a far more
refined response than circuit-breaker-switched capacitors. Static synchronous compensators take this a
step further by achieving reactive power adjustments using only power electronics.
Power electronics are semiconductor based devices that are able to
switch quantities of power ranging from a few hundred watts to several hundred megawatts. Despite
their relatively simple function, their speed of operation (typically in the order of nanoseconds) means
they are capable of a wide range of tasks that would be difficult or impossible with conventional
technology. The classic function of power electronics is rectification, or the conversion of AC-to-DC
power, power electronics are therefore found in almost every digital device that is supplied from an AC
source either as an adapter that plugs into the wall (see photo) or as component internal to the device.
High-powered power electronics can also be used to convert AC power to DC power for long distance
transmission in a system known as HVDC. HVDC is used because it proves to be more economical than
similar high voltage AC systems for very long distances (hundreds to thousands of kilometres). HVDC is
also desirable for interconnects because it allows frequency independence thus improving system
stability. Power electronics are also essential for any power source that is required to produce an AC
output but that by its nature produces a DC output. They are therefore used by photovoltaic
installations.
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Power electronics also feature in a wide range of more
exotic uses. They are at the heart of all modern electric and hybrid vehicles—where they are used for
both motor control and as part of the brushless DC motor. Power electronics are also found in
practically all modern petrol-powered vehicles, this is because the power provided by the car's batteries
alone is insufficient to provide ignition, air-conditioning, internal lighting, radio and dashboard displays
for the life of the car. So the batteries must be recharged while driving—a feat that is typically
accomplished using power electronics. Whereas conventional technology would be unsuitable for a
modern electric car, commutators can and have been used in petrol-powered cars, the switch to
alternators in combination with power electronics has occurred because of the improved durability of
brushless machinery.
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Some electric railway systems also use DC power and thus make
use of power electronics to feed grid power to the locomotives and often for speed control of the
locomotive's motor. In the middle twentieth century, rectifier locomotives were popular, these used
power electronics to convert AC power from the railway network for use by a DC motor.[38] Today most
electric locomotives are supplied with AC power and run using AC motors, but still use power electronics
to provide suitable motor control. The use of power electronics to assist with the motor control and
with starter circuits, in addition to rectification, is responsible for power electronics appearing in a wide
range of industrial machinery. Power electronics even appear in modern residential air conditioners
allow are at the heart of the variable speed wind turbine.
Power systems contain protective devices to prevent injury or
damage during failures. The quintessential protective device is the fuse. When the current through a
fuse exceeds a certain threshold, the fuse element melts, producing an arc across the resulting gap that
is then extinguished, interrupting the circuit. Given that fuses can be built as the weak point of a system,
fuses are ideal for protecting circuitry from damage. Fuses however have two problems: First, after they
have functioned, fuses must be replaced as they cannot be reset. This can prove inconvenient if the fuse
is at a remote site or a spare fuse is not on hand. And second, fuses are typically inadequate as the sole
safety device in most power systems as they allow current flows well in excess of that that would prove
lethal to a human or animal.
The first problem is resolved by the use of circuit
breakers—devices that can be reset after they have broken current flow. In modern systems that use
less than about 10 kW, miniature circuit breakers are typically used. These devices combine the
mechanism that initiates the trip (by sensing excess current) as well as the mechanism that breaks the
current flow in a single unit. Some miniature circuit breakers operate solely on the basis of
electromagnetism. In these miniature circuit breakers, the current is run through a solenoid, and, in the
event of excess current flow, the magnetic pull of the solenoid is sufficient to force open the circuit
breaker's contacts (often indirectly through a tripping mechanism). A better design, however, arises by
inserting a bimetallic strip before the solenoid—this means that instead of always producing a magnetic
force, the solenoid only produces a magnetic force when the current is strong enough to deform the
bimetallic strip and complete the solenoid's circuit.
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In higher powered applications, the
protective relays that detect a fault and initiate a trip are separate from the circuit breaker. Early relays
worked based upon electromagnetic principles similar to those mentioned in the previous paragraph,
modern relays are application-specific computers that determine whether to trip based upon readings
from the power system. Different relays will initiate trips depending upon different protection schemes.
For example, an overcurrent relay might initiate a trip if the current on any phase exceeds a certain
threshold whereas a set of differential relays might initiate a trip if the sum of currents between them
indicates there may be current leaking to earth. The circuit breakers in higher powered applications are
different too. Air is typically no longer sufficient to quench the arc that forms when the contacts are
forced open so a variety of techniques are used. One of the most popular techniques is to keep the
chamber enclosing the contacts flooded with sulfur hexafluoride (SF6)—a non-toxic gas with sound arcquenching properties. Other techniques are discussed in the reference.
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The second problem, the inadequacy of fuses to act as the sole
safety device in most power systems, is probably best resolved by the use of residual current devices
(RCDs). In any properly functioning electrical appliance, the current flowing into the appliance on the
active line should equal the current flowing out of the appliance on the neutral line. A residual current
device works by monitoring the active and neutral lines and tripping the active line if it notices a
difference.[40] Residual current devices require a separate neutral line for each phase and to be able to
trip within a time frame before harm occurs. This is typically not a problem in most residential
applications where standard wiring provides an active and neutral line for each appliance (that's why
your power plugs always have at least two tongs) and the voltages are relatively low however these
issues limit the effectiveness of RCDs in other applications such as industry. Even with the installation of
an RCD, exposure to electricity can still prove fatal.
SCADA systems
In large electric power systems, supervisory control and data
acquisition (SCADA) is used for tasks such as switching on generators, controlling generator output and
switching in or out system elements for maintenance. The first supervisory control systems
implemented consisted of a panel of lamps and switches at a central console near the controlled plant.
The lamps provided feedback on the state of the plant (the data acquisition function) and the switches
allowed adjustments to the plant to be made (the supervisory control function). Today, SCADA systems
are much more sophisticated and, due to advances in communication systems, the consoles controlling
the plant no longer need to be near the plant itself. Instead, it is now common for plants to be
controlled with equipment similar (if not identical) to a desktop computer. The ability to control such
plants through computers has increased the need for security—there have already been reports of
cyber-attacks on such systems causing significant disruptions to power systems.
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Despite their common components, power systems vary widely
both with respect to their design and how they operate. This section introduces some common power
system types and briefly explains their operation.
Residential power systems
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Residential dwellings almost always take supply from the low
voltage distribution lines or cables that run past the dwelling. These operate at voltages of between 110
and 260 volts (phase-to-earth) depending upon national standards. A few decades ago small dwellings
would be fed a single phase using a dedicated two-core service cable (one core for the active phase and
one core for the neutral return). The active line would then be run through a main isolating switch in the
fuse box and then split into one or more circuits to feed lighting and appliances inside the house. By
convention, the lighting and appliance circuits are kept separate so the failure of an appliance does not
leave the dwelling's occupants in the dark. All circuits would be fused with an appropriate fuse based
upon the wire size used for that circuit. Circuits would have both an active and neutral wire with both
the lighting and power sockets being connected in parallel. Sockets would also be provided with a
protective earth. This would be made available to appliances to connect to any metallic casing. If this
casing were to become live, the theory is the connection to earth would cause an RCD or fuse to trip—
thus preventing the future electrocution of an occupant handling the appliance. Earthing systems vary
between regions, but in countries such as the United Kingdom and Australia both the protective earth
and neutral line would be earthed together near the fuse box before the main isolating switch and the
neutral earthed once again back at the distribution transformer.
There have been a number of minor changes over the years to
practice of residential wiring. Some of the most significant ways modern residential power systems in
developed countries tend to vary from older ones include:
For convenience, miniature circuit breakers are now almost always
used in the fuse box instead of fuses as these can easily be reset by occupants and, if of the
thermomagnetic type, can respond more quickly to some types of fault.
For safety reasons, RCDs are now often installed on appliance circuits
and, increasingly, even on lighting circuits.
Whereas residential air conditioners of the past might have been fed
from a dedicated circuit attached to a single phase, larger centralised air conditioners that require threephase power are now becoming common in some countries.
Protective earths are now run with lighting circuits to allow for metallic lamp holders to be earthed.
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Increasingly residential power systems are incorporating microgenerators,
most notably, photovoltaic cells.
Commercial power systems
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Commercial power systems such as shopping centers or high-rise
buildings are larger in scale than residential systems. Electrical designs for larger commercial systems
are usually studied for load flow, short-circuit fault levels, and voltage drop for steady-state loads and
during starting of large motors. The objectives of the studies are to assure proper equipment and
conductor sizing, and to coordinate protective devices so that minimal disruption is caused when a fault
is cleared. Large commercial installations will have an orderly system of sub-panels, separate from the
main distribution board to allow for better system protection and more efficient electrical installation.
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Typically one of the largest appliances connected to a commercial power
system in hot climates is the HVAC unit, and ensuring this unit is adequately supplied is an important
consideration in commercial power systems. Regulations for commercial establishments place other
requirements on commercial systems that are not placed on residential systems. For example, in
Australia, commercial systems must comply with AS 2293, the standard for emergency lighting, which
requires emergency lighting be maintained for at least 90 minutes in the event of loss of mains supply.
In the United States, the National Electrical Code requires commercial systems to be built with at least
one 20 A sign outlet in order to light outdoor signage. Building code regulations may place special
requirements on the electrical system for emergency lighting, evacuation, emergency power, smoke
control and fire protection.
Power system management
Power system management varies depending upon the power
system. Residential power systems and even automotive electrical systems are often run-to-fail. In
aviation, the power system uses redundancy to ensure availability. On the Boeing 747-400 any of the
four engines can provide power and circuit breakers are checked as part of power-up (a tripped circuit
breaker indicating a fault). Larger power systems require active management. In industrial plants or
mining sites a single team might be responsible for fault management, augmentation and maintenance.
Where as for the electric grid, management is divided amongst several specialised teams.
Fault management
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Fault management involves monitoring the behaviour of the power
system so as to identify and correct issues that affect the system's reliability. Fault management can be
specific and reactive: for example, dispatching a team to restring conductor that has been brought down
during a storm. Or, alternatively, can focus on systemic improvements: such as the installation of
reclosers on sections of the system that are subject to frequent temporary disruptions (as might be
caused by vegetation, lightning or wildlife).
Maintenance and augmentation
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In addition to fault management, power systems may
require maintenance or augmentation. As often it is neither economical nor practical for large parts of
the system to be offline during this work, power systems are built with many switches. These switches
allow the part of the system being worked on to be isolated while the rest of the system remains live. At
high voltages, there are two switches of note: isolators and circuit breakers. Circuit breakers are loadbreaking switches where as operating isolators under load would lead to unacceptable and dangerous
arcing. In a typical planned outage, several circuit breakers are tripped to allow the isolators to be
switched before the circuit breakers are again closed to reroute power around the isolated area. This
allows work to be completed on the isolated area.
Frequency and voltage management
Beyond fault management and maintenance one of the
main difficulties in power systems is that the active power consumed plus losses must equal the active
power produced. If load is reduced while generation inputs remain constant the synchronous generators
will spin faster and the system frequency will rise. The opposite occurs if load is increased. As such the
system frequency must be actively managed primarily through switching on and off dispatchable loads
and generation. Making sure the frequency is constant is usually the task of a system operator. Even
with frequency maintained, the system operator can be kept occupied ensuring:
Underwater accent lighting is also used for koi ponds, fountains, swimming pools and the like.
Neon signs are most often used to attract attention rather than to illuminate.
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A smartphone is a mobile device that combines cellular and
mobile computing functions into one unit. They are distinguished from feature phones by their stronger
hardware capabilities and extensive mobile operating systems, which facilitate wider software, internet
(including web browsing[1] over mobile broadband), and multimedia functionality (including music,
video, cameras, and gaming), alongside core phone functions such as voice calls and text messaging.
Smartphones typically contain a number of metal–oxide–semiconductor (MOS) integrated circuit (IC)
chips, include various sensors that can be leveraged by their software (such as a magnetometer,
proximity sensors, barometer, gyroscope, or accelerometer), and support wireless communications
protocols (such as Bluetooth, Wi-Fi, or satellite navigation).
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In the context of spaceflight, a satellite is an object that has been
intentionally placed into orbit. These objects are called artificial satellites to distinguish them from
natural satellites such as Earth's Moon.
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On 4 October 1957 the Soviet Union launched the
world's first artificial satellite, Sputnik 1. Since then, about 8,900 satellites from more than 40 countries
have been launched. According to a 2018 estimate, some 5,000 remain in orbit. Of those, about 1,900
were operational, while the rest have exceeded their useful lives and become space debris.
Approximately 63% of operational satellites are in low Earth orbit, 6% are in medium-Earth orbit (at
20,000 km), 29% are in geostationary orbit (at 36,000 km) and the remaining 2% are in various elliptical
orbits. In terms of countries with the most satellites, the USA has the most with 859 satellites, China is
second with 250, and Russia third with 146. These are then followed by India (118), Japan (72) and the
UK (52). A few large space stations, including the International Space Station, have been launched in
parts and assembled in orbit. Over a dozen space probes have been placed into orbit around other
bodies and become artificial satellites of the Moon, Mercury, Venus, Mars, Jupiter, Saturn, a few
asteroids, a comet and the Sun.
Satellites are used for many purposes. Among several other
applications, they can be used to make star maps and maps of planetary surfaces, and also take pictures
of planets they are launched into. Common types include military and civilian Earth observation
satellites, communications satellites, navigation satellites, weather satellites, and space telescopes.
Space stations and human spacecraft in orbit are also satellites.
Satellites can operate by themselves or as part of a larger system, a
satellite formation or satellite constellation.
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Satellite orbits vary greatly, depending on the purpose of the
satellite, and are classified in a number of ways. Well-known (overlapping) classes include low Earth
orbit, polar orbit, and geostationary orbit.
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A launch vehicle is a rocket that places a satellite into orbit. Usually, it
lifts off from a launch pad on land. Some are launched at sea from a submarine or a mobile maritime
platform, or aboard a plane (see air launch to orbit).
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Satellites are usually semi-independent computer-controlled
systems. Satellite subsystems attend many tasks, such as power generation, thermal control, telemetry,
attitude control, scientific instrumentation, communication, etc.
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Information and communications technology (ICT) is an
extensional term for information technology (IT) that stresses the role of unified communications and
the integration of telecommunications (telephone lines and wireless signals) and computers, as well as
necessary enterprise software, middleware, storage and audiovisual, that enable users to access, store,
transmit, and manipulate information.
computer is a machine that can be instructed to carry
out sequences of arithmetic or logical operations automatically via computer programming. Modern
computers have the ability to follow generalized sets of operations, called programs. These programs
enable computers to perform an extremely wide range of tasks. A "complete" computer including the
hardware, the operating system (main software), and peripheral equipment required and used for "full"
operation can be referred to as a computer system. This term may as well be used for a group of
computers that are connected and work together, in particular a computer network or computer
cluster.
Computers are used as control systems for a wide variety of
industrial and consumer devices. This includes simple special purpose devices like microwave ovens and
remote controls, factory devices such as industrial robots and computer-aided design, and also general
purpose devices like personal computers and mobile devices such as smartphones. The Internet is run
on computers and it connects hundreds of millions of other computers and their users.
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Early computers were only conceived as calculating
devices. Since ancient times, simple manual devices like the abacus aided people in doing calculations.
Early in the Industrial Revolution, some mechanical devices were built to automate long tedious tasks,
such as guiding patterns for looms. More sophisticated electrical machines did specialized analog
calculations in the early 20th century. The first digital electronic calculating machines were developed
during World War II. The first semiconductor transistors in the late 1940s were followed by the siliconbased MOSFET (MOS transistor) and monolithic integrated circuit (IC) chip technologies in the late
1950s, leading to the microprocessor and the microcomputer revolution in the 1970s. The speed, power
and versatility of computers have been increasing dramatically ever since then, with transistor counts
increasing at a rapid pace (as predicted by Moore's law), leading to the Digital Revolution during the late
20th to early 21st centuries.
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Conventionally, a modern computer consists of at least
one processing element, typically a central processing unit (CPU) in the form of a microprocessor, along
with some type of computer memory, typically semiconductor memory chips. The processing element
carries out arithmetic and logical operations, and a sequencing and control unit can change the order of
operations in response to stored information. Peripheral devices include input devices (keyboards, mice,
joystick, etc.), output devices (monitor screens, printers, etc.), and input/output devices that perform
both functions (e.g., the 2000s-era touchscreen). Peripheral devices allow information to be retrieved
from an external source and they enable the result of operations to be saved and retrieved.
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Wi-Fi is a family of wireless network protocols,
based on the IEEE 802.11 family of standards, which are commonly used for local area networking of
devices and Internet access. Wi‑Fi is a trademark of the non-profit Wi-Fi Alliance, which restricts the use
of the term Wi-Fi Certified to products that successfully complete interoperability certification testing.
As of 2017, the Wi-Fi Alliance consisted of more than 800 companies from around the world. As of 2019,
over 3.05 billion Wi-Fi enabled devices are shipped globally each year. Devices that can use Wi-Fi
technologies include personal computer desktops and laptops, smartphones and tablets, smart TVs,
printers, smart speakers, cars, and drones.
Telecommunications Engineering is an engineering discipline
centered on electrical and computer engineering which seeks to support and enhance
telecommunication systems. The work ranges from basic circuit design to strategic mass developments.
A telecommunication engineer is responsible for designing and overseeing the installation of
telecommunications equipment and facilities, such as complex electronic switching systems, and other
plain old telephone service facilities, optical fiber cabling, IP networks, and microwave transmission
systems. Telecommunications engineering also overlaps with broadcast engineering.
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Over several years starting in 1894 the Italian inventor
Guglielmo Marconi built the first complete, commercially successful wireless telegraphy system based
on airborne electromagnetic waves (radio transmission). In December 1901, he would go on to
established wireless communication between Britain and Newfoundland, earning him the Nobel Prize in
physics in 1909 (which he shared with Karl Braun). In 1900 Reginald Fessenden was able to wirelessly
transmit a human voice. On March 25, 1925, Scottish inventor John Logie Baird publicly demonstrated
the transmission of moving silhouette pictures at the London department store Selfridges. In October
1925, Baird was successful in obtaining moving pictures with halftone shades, which were by most
accounts the first true television pictures. This led to a public demonstration of the improved device on
26 January 1926 again at Selfridges. Baird's first devices relied upon the Nipkow disk and thus became
known as the mechanical television. It formed the basis of semi-experimental broadcasts done by the
British Broadcasting Corporation beginning September 30, 1929.
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Samuel morse independently developed a version of the
electrical telegraph that he unsuccessfully demonstrated on 2 September 1837. Soon after he was
joined by Alfred Vail who developed the register — a telegraph terminal that integrated a logging device
for recording messages to paper tape. This was demonstrated successfully over three miles (five
kilometres) on 6 January 1838 and eventually over forty miles (sixty-four kilometres) between
Washington, D.C. and Baltimore on 24 May 1844. The patented invention proved lucrative and by 1851
telegraph lines in the United States spanned over 20,000 miles (32,000 kilometres).
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The first successful transatlantic telegraph cable was
completed on 27 July 1866, allowing transatlantic telecommunication for the first time. Earlier
transatlantic cables installed in 1857 and 1858 only operated for a few days or weeks before they failed.
The international use of the telegraph has sometimes been dubbed the "Victorian Internet".
The first commercial telephone services were set up in 1878 and
1879 on both sides of the Atlantic in the cities of New Haven and London. Alexander Graham Bell held
the master patent for the telephone that was needed for such services in both countries. The
technology grew quickly from this point, with inter-city lines being built and telephone exchanges in
every major city of the United States by the mid-1880s. Despite this, transatlantic voice communication
remained impossible for customers until January 7, 1927 when a connection was established using
radio. However no cable connection existed until TAT-1 was inaugurated on September 25, 1956
providing 36 telephone circuits.
In 1880, Bell and co-inventor Charles Sumner Tainter
conducted the world's first wireless telephone call via modulated lightbeams projected by photophones.
The scientific principles of their invention would not be utilized for several decades, when they were
first deployed in military and fiber-optic communications
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On 11 September 1940, George Stibitz was able to transmit problems
using teleprinter to his Complex Number Calculator in New York and receive the computed results back
at Dartmouth College in New Hampshire. This configuration of a centralized computer or mainframe
computer with remote "dumb terminals" remained popular throughout the 1950s and into the 1960s.
However, it was not until the 1960s that researchers started to investigate packet switching — a
technology that allows chunks of data to be sent between different computers without first passing
through a centralized mainframe. A four-node network emerged on 5 December 1969. This network
soon became the ARPANET, which by 1981 would consist of 213 nodes.
Optical fiber
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ARPANET's development centered around the Request for
Comment process and on 7 April 1969, RFC 1 was published. This process is important because ARPANET
would eventually merge with other networks to form the Internet, and many of the communication
protocols that the Internet relies upon today were specified through the Request for Comment process.
In September 1981, RFC 791 introduced the Internet Protocol version 4 (IPv4) and RFC 793 introduced
the Transmission Control Protocol (TCP) — thus creating the TCP/IP protocol that much of the Internet
relies upon today.
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Optical fiber can be used as a medium for telecommunication and
computer networking because it is flexible and can be bundled into cables. It is especially advantageous
for long-distance communications, because light propagates through the fiber with little attenuation
compared to electrical cables. This allows long distances to be spanned with few repeaters.
In 1966 Charles K. Kao and George Hockham proposed
optical fibers at STC Laboratories (STL) at Harlow, England, when they showed that the losses of 1000
dB/km in existing glass (compared to 5-10 dB/km in coaxial cable) was due to contaminants, which could
potentially be removed.
Optical fiber was successfully developed in 1970 by Corning
Glass Works, with attenuation low enough for communication purposes (about 20dB/km), and at the
same time GaAs (Gallium arsenide) semiconductor lasers were developed that were compact and
therefore suitable for transmitting light through fiber optic cables for long distances.
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After a period of research starting from 1975, the first
commercial fiber-optic communications system was developed, which operated at a wavelength around
0.8 µm and used GaAs semiconductor lasers. This first-generation system operated at a bit rate of 45
Mbps with repeater spacing of up to 10 km. Soon on 22 April 1977, General Telephone and Electronics
sent the first live telephone traffic through fiber optics at a 6 Mbit/s throughput in Long Beach,
California.
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The first wide area network fibre optic cable system in the world
seems to have been installed by Rediffusion in Hastings, East Sussex, UK in 1978. The cables were placed
in ducting throughout the town, and had over 1000 subscribers. They were used at that time for the
transmission of television channels, not available because of local reception problems.
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The first transatlantic telephone cable to use optical fiber was TAT-8, based on Desurvire optimized laser
amplification technology. It went into operation in 1988.
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In the late 1990s through 2000, industry promoters, and research
companies such as KMI, and RHK predicted massive increases in demand for communications bandwidth
due to increased use of the Internet, and commercialization of various bandwidth-intensive consumer
services, such as video on demand. Internet protocol data traffic was increasing exponentially, at a
faster rate than integrated circuit complexity had increased under Moore's Law.
Transmitter
Transmitter (information source) that takes information and
converts it to a signal for transmission. In electronics and telecommunications a transmitter or radio
transmitter is an electronic device which, with the aid of an antenna, produces radio waves. In addition
to their use in broadcasting, transmitters are necessary component parts of many electronic devices
that communicate by radio, such as cell phones,
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Transmission medium over which the signal is transmitted.
For example, the transmission medium for sounds is usually air, but solids and liquids may also act as
transmission media for sound. Many transmission media are used as communications channel. One of
the most common physical medias used in networking is copper wire. Copper wire is used to carry
signals to long distances using relatively low amounts of power. Another example of a physical medium
is optical fiber, which has emerged as the most commonly used transmission medium for long-distance
communications. Optical fiber is a thin strand of glass that guides light along its length.
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The absence of a material medium in vacuum may also constitute a
transmission medium for electromagnetic waves such as light and radio waves.
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Receiver (information sink) that receives and converts the signal
back into required information. In radio communications, a radio receiver is an electronic device that
receives radio waves and converts the information carried by them to a usable form. It is used with an
antenna. The information produced by the receiver may be in the form of sound (an audio signal),
images (a video signal) or digital data.
Wired communications make use of underground communications
cables (less often, overhead lines), electronic signal amplifiers (repeaters) inserted into connecting
cables at specified points, and terminal apparatus of various types, depending on the type of wired
communications used.
Wireless communication involves the transmission of information
over a distance without help of wires, cables or any other forms of electrical conductors. Wireless
operations permit services, such as long-range communications, that are impossible or impractical to
implement with the use of wires. The term is commonly used in the telecommunications industry to
refer to telecommunications systems (e.g. radio transmitters and receivers, remote controls etc.) which
use some form of energy (e.g. radio waves, acoustic energy, etc.) to transfer information without the
use of wires. Information is transferred in this manner over both short and long distances.
Power system protection is a branch of electrical power
engineering that deals with the protection of electrical power systems from faults through the
disconnection of faulted parts from the rest of the electrical network. The objective of a protection
scheme is to keep the power system stable by isolating only the components that are under fault, whilst
leaving as much of the network as possible still in operation. Thus, protection schemes must apply a very
pragmatic and pessimistic approach to clearing system faults. The devices that are used to protect the
power systems from faults are called protection devices.
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Power system protection is a branch of electrical power
engineering that deals with the protection of electrical power systems from faults through the
disconnection of faulted parts from the rest of the electrical network. The objective of a protection
scheme is to keep the power system stable by isolating only the components that are under fault, whilst
leaving as much of the network as possible still in operation. Thus, protection schemes must apply a very
pragmatic and pessimistic approach to clearing system faults. The devices that are used to protect the
power systems from faults are called protection devices.
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An electric vehicle (EV), also called electrics is a vehicle that uses one or
more electric motors or traction motors for propulsion. An electric vehicle may be powered through a
collector system by electricity from off-vehicle sources, or may be self-contained with a battery, solar
panels, fuel cells or an electric generator to convert fuel to electricity. EVs include, but are not limited to,
road and rail vehicles, surface and underwater vessels, electric aircraft and electric spacecraft.
EVs first came into existence in the mid-19th century, when
electricity was among the preferred methods for motor vehicle propulsion, providing a level of comfort
and ease of operation that could not be achieved by the gasoline cars of the time. Modern internal
combustion engines have been the dominant propulsion method for motor vehicles for almost 100
years, but electric power has remained commonplace in other vehicle types, such as trains and smaller
vehicles of all types.
Commonly, the term EV is used to refer to an electric car. In the 21st
century, EVs have seen a resurgence due to technological developments, and an increased focus on
renewable energy and the potential reduction of transportation's impact on climate change and other
environmental issues. Project Drawdown describes electric vehicles as one of the 100 best
contemporary solutions for addressing climate change.
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Government incentives to increase adoption were first introduced in the late2000s, including in the United States and the European Union, leading to a growing market for the
vehicles in the 2010s. And increasing consumer interest and awareness and structural incentives, such
as those being built into the green recovery from the COVID-19 pandemic, is expected to greatly
increase the electric vehicle market. A pre-COVID 2019 analysis, projected that Electric vehicles are
expected to increase from 2% of global share in 2016 to 22% in 2030. Much of this market growth is
expected in markets like North America and Europe; a 2020 literature review, suggested that growth in
use of electric vehicles, especially electric personal vehicles, currently appears economically unlikely in
developing economies.
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Electric motive power started in 1827, when Hungarian priest Ányos
Jedlik built the first crude but viable electric motor, provided with stator, rotor and commutator, and the
year after he used it to power a tiny car. A few years later, in 1835, professor Sibrandus Stratingh of the
University of Groningen, the Netherlands, built a small-scale electric car, and between 1832 and 1839
(the exact year is uncertain), Robert Anderson of Scotland invented the first crude electric carriage,
powered by non-rechargeable primary cells. Around the same period, early experimental electrical cars
were moving on rails, too. American blacksmith and inventor Thomas Davenport built a toy electric
locomotive, powered by a primitive electric motor, in 1835. In 1838, a Scotsman named Robert
Davidson built an electric locomotive that attained a speed of four miles per hour (6 km/h). In England a
patent was granted in 1840 for the use of rails as conductors of electric current, and similar American
patents were issued to Lilley and Colten in 1847.
The first mass-produced electric vehicles appeared in America in the
early 1900s. In 1902, "Studebaker Automobile Company" entered the automotive business with electric
vehicles, though it also entered the gasoline vehicles market in 1904. However, with the advent of cheap
assembly line cars by Ford, electric cars fell to the wayside
Due to the limitations of storage batteries at that time, electric
cars did not gain much popularity, however electric trains gained immense popularity due to their
economies and fast speeds achievable. By the 20th century, electric rail transport became commonplace
due to advances in the development of electric locomotives. Over time their general-purpose
commercial use reduced to specialist roles, as platform trucks, forklift trucks, ambulances, tow tractors
and urban delivery vehicles, such as the iconic British milk float; for most of the 20th century, the UK
was the world's largest user of electric road vehicles.
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Electrified trains were used for coal transport, as the motors did
not use precious oxygen in the mines. Switzerland's lack of natural fossil resources forced the rapid
electrification of their rail network. One of the earliest rechargeable batteries – the nickel-iron battery –
was favored by Edison for use in electric cars.
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EVs were among the earliest automobiles, and before the
preeminence of light, powerful internal combustion engines, electric automobiles held many vehicle
land speed and distance records in the early 1900s. They were produced by Baker Electric, Columbia
Electric, Detroit Electric, and others, and at one point in history out-sold gasoline-powered vehicles. In
fact, in 1900, 28 percent of the cars on the road in the USA were electric. EVs were so popular that even
President Woodrow Wilson and his secret service agents toured Washington, DC, in their Milburn
Electrics, which covered 60–70 mi (100–110 km) per charge.
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A number of developments contributed to decline of electric
cars. Improved road infrastructure required a greater range than that offered by electric cars, and the
discovery of large reserves of petroleum in Texas, Oklahoma, and California led to the wide availability
of affordable gasoline/petrol, making internal combustion powered cars cheaper to operate over long
distances. Also internal combustion powered cars became ever easier to operate thanks to the invention
of the electric starter by Charles Kettering in 1912, which eliminated the need of a hand crank for
starting a gasoline engine, and the noise emitted by ICE cars became more bearable thanks to the use of
the muffler, which Hiram Percy Maxim had invented in 1897. As roads were improved outside urban
areas electric vehicle range could not compete with the ICE. Finally, the initiation of mass production of
gasoline-powered vehicles by Henry Ford in 1913 reduced significantly the cost of gasoline cars as
compared to electric cars.
In the 1930s, National City Lines, which was a partnership of General
Motors, Firestone, and Standard Oil of California purchased many electric tram networks across the
country to dismantle them and replace them with GM buses. The partnership was convicted of
conspiring to monopolize the sale of equipment and supplies to their subsidiary companies, but were
acquitted of conspiring to monopolize the provision of transportation services.
This 1973 photo of a charging station in Seattle shows an AMC Gremlin
modified to take electric power; it had a range of about 50 miles on one charge.
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The emergence of metal–oxide–semiconductor (MOS)
technology led to the development of modern electric road vehicles. The MOSFET (MOS field-effect
transistor, or MOS transistor), invented by Mohamed M. Atalla and Dawon Kahng at Bell Labs in
1959,led to the development of the power MOSFET by Hitachi in 1969,[22] and the single-chip
microprocessor by Federico Faggin, Marcian Hoff, Masatoshi Shima and Stanley Mazor at Intel in 1971.
The power MOSFET and the microcontroller, a type of single-chip microprocessor, led to significant
advances in electric vehicle technology. MOSFET power converters allowed operation at much higher
switching frequencies, made it easier to drive, reduced power losses, and significantly reduced prices,
while single-chip microcontrollers could manage all aspects of the drive control and had the capacity for
battery management. This IGBT technology made the possible use of the synecious AC three phase
motor, by creating a synthetic three phase AC from the nominal 400 Volt DC traction battery pack, all
inside the "Dolphin" Motor Controller. This improvement was developed by Hughes and GM and used in
their US Electricar in 1995, but still used the heaver (26 count 12 Volt) lead acid batteries all connected
in series. GM later developed an electric PU truck and then the EV1. This motor and controller was kept
alive and used in converted cars by AC Propulsion, where they introduced the lithium battery and later
Elon Musk saw and embraced. Another important technology that enabled modern highway-capable
electric cars is the lithium-ion battery, invented by John Goodenough, Rachid Yazami and Akira Yoshino
in the 1980s, which was responsible for the development of electric vehicles capable of long-distance
travel.
In January 1990, General Motors' President introduced its EV
concept two-seater, the "Impact", at the Los Angeles Auto Show. That September, the California Air
Resources Board mandated major-automaker sales of EVs, in phases starting in 1998. From 1996 to
1998 GM produced 1117 EV1s, 800 of which were made available through three-year leases.[26]
Chrysler, Ford, GM, Honda, and Toyota also produced limited
numbers of EVs for California drivers. In 2003, upon the expiration of GM's EV1 leases, GM discontinued
them. The discontinuation has variously been attributed to:
the auto industry's successful federal court challenge to California's zero-emissions vehicle mandate,
a federal regulation requiring GM to produce and maintain spare parts for the few thousands EV1s and
the success of the oil and auto industries' media campaign to reduce public acceptance of EVs.
General Motors EV1 electric car (1996–1998), story told in movie Who Killed the Electric Car?
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A movie made on the subject in 2005–2006 was titled Who Killed the
Electric Car? and released theatrically by Sony Pictures Classics in 2006. The film explores the roles of
automobile manufacturers, oil industry, the U.S. government, batteries, hydrogen vehicles, and
consumers, and each of their roles in limiting the deployment and adoption of this technology.
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Ford released a number of their Ford Ecostar delivery vans into
the market. Honda, Nissan and Toyota also repossessed and crushed most of their EVs, which, like the
GM EV1s, had been available only by closed-end lease. After public protests, Toyota sold 200 of its RAV
EVs to eager buyers; they later sold at over their original forty-thousand-dollar price. This lesson did not
go unlearned; BMW of Canada sold off a number of Mini EVs when their Canadian testing ended.
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The production of the Citroën Berlingo Electrique stopped in September 2005.
Public transport, goods delivery, private transport and pedestrians in Leidsestraat, Amsterdam
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Carbon neutral fuelElectric vehicleGreen vehiclePlug-in
hybridRoad traffic safetySustainable transportTransportation demand management
During the last few decades, environmental impact of the
petroleum-based transportation infrastructure, along with the fear of peak oil, has led to renewed
interest in an electric transportation infrastructure. EVs differ from fossil fuel-powered vehicles in that
the electricity they consume can be generated from a wide range of sources, including fossil fuels,
nuclear power, and renewable sources such as tidal power, solar power, hydropower, and wind power
or any combination of those. The carbon footprint and other emissions of electric vehicles varies
depending on the fuel and technology used for electricity generation. The electricity may then be stored
on board the vehicle using a battery, flywheel, or supercapacitors. Vehicles making use of engines
working on the principle of combustion can usually only derive their energy from a single or a few
sources, usually non-renewable fossil fuels. A key advantage of hybrid or plug-in electric vehicles is
regenerative braking, which recovers kinetic energy, typically lost during friction braking as heat, as
electricity restored to the on-board battery.
As of January 2018, the world's two best selling all-electric cars in
history were the Nissan Leaf (left), with 300,000 in global sales[30] and the Tesla Model S (right), with
over 200,000 in global sales.
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As of March 2018, there are some 45 series production highwaycapable all-electric cars available in various countries. As of early December 2015, the Leaf, with 200,000
units sold worldwide, was the world's top-selling highway-capable all-electric car of all time, followed by
the Tesla Model S with global deliveries of about 100,000 units. Leaf global sales achieved the 300,000
unit milestone in January 2018.
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As of May 2015, more than 500,000 highway-capable all-electric
passenger cars and light utility vehicles had been sold worldwide since 2008, out of total global sales of
about 850,000 light-duty plug-in electric vehicles. As of May 2015, the United States had the largest fleet
of highway-capable plug-in electric vehicles in the world, with about 335,000 highway legal plug-in
electric cars sold in the country since 2008, and representing about 40% of the global stock. California is
the largest plug-in car regional market in the country, with almost 143,000 units sold between
December 2010 and March 2015, representing over 46% of all plug-in cars sold in the U.S. Cumulative
global sales of all-electric cars and vans passed the 1 million unit milestone in September 2016.
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Norway is the country with the highest market penetration per capita in
the world, with four plug-in electric vehicles per 1000 inhabitants in 2013. In March 2014, Norway
became the first country where over 1 in every 100 passenger cars on the roads is a plug-in electric. In
2016, 29% of all new car sales in the country were battery-powered or plug-in hybrids. Norway also had
the world's largest plug-in electric segment market share of total new car sales, 13.8% in 2014, up from
5.6% in 2013. In June 2016, Andorra became the second country in this list, with a 6% of market share
combining electric vehicles and plug-in hybrids due to a strong public policy providing multiple
advantages. By the end of 2016, Norway's 100,000th battery-powered car was sold.
In April 2019, the Chinese company BYD Auto launched the
first electric bi-articulated bus, the BYD K12A. The bus will operate as a test in TransMilenio, the BRT
system of Bogotá, Colombia in August 2019. By some estimates electric vehicles sales may constitute
almost a third of new-car sales by the end of 2030.
In 2008 Ferdinand Dudenhoeffer, head of the Centre of Automotive
Research at the Gelsenkirchen University of Applied Sciences in Germany, predicted that "by 2025, all
passenger cars sold in Europe will be electric or hybrid electric".
Improved batteries
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Advances in lithium ion batteries, driven at first by the consumer
electronics industry, allow full-sized, highway-capable EVs to travel nearly as far on a single charge as
conventional cars go on a single tank of gasoline. Lithium batteries have been made safe, can be
recharged in minutes instead of hours (see recharging time), and now last longer than the typical vehicle
(see lifespan). The production cost of these lighter, higher-capacity lithium batteries is gradually
decreasing as the technology matures and production volumes increase (see price history).
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Many companies and researchers are also working on newer battery
technologies, including solid state batteries and alternate technologies.
Electric trucks
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Another improvement is to decouple the electric motor from the
battery through electronic control, employing supercapacitors to buffer large but short power demands
and regenerative braking energy. The development of new cell types combined with intelligent cell
management improved both weak points mentioned above. The cell management involves not only
monitoring the health of the cells but also a redundant cell configuration (one more cell than needed).
With sophisticated switched wiring it is possible to condition one cell while the rest are on duty.
Small electric trucks have been used for decades for specific and/or limited uses, such as Milk floats or
the electric Renault Maxity.
Larger electric trucks have been made in the 2010s, such as
prototypes of electric Renault Midlum tested in real conditions and trucks by E-Force One and Emoss.
Mercedes-Benz, a division of Daimler, began delivering ten eActros units to customers in September
2018 for a two-year real-world test. DAF, a division of Paccar, delivered its first CF articulated truck to
Jumbo for testing in December 2018.
Fuso, a division of Daimler, began deliveries of the eCanter in
2017.Freightliner, another division of Daimler, began delivering e-M2 trucks to Penske in December
2018, and will commercialise its larger e-Cascadia in 2019. MAN, a division of Volkswagen AG, delivered
its first unit of its e-TGM articulated truck to Porsche in December 2018, larger-scale production is
scheduled to begin in 2019.
Renault and Volvo hoped to launch their first mass-produced electric trucks in
early 2019.
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Announced in 2017, the Tesla Semi was expected to hit production lines in 2019.
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Particularly in Europe, fuel-cell electric trains are gaining in popularity to
replace diesel-electric units. In Germany, several Länder have ordered Alstom Coradia iLINT trainsets, in
service since 2018, with France also planning to order trainsets. The United Kingdom, the Netherlands,
Denmark, Norway, Italy, Canada and Mexico are equally interested. In France, the SNCF plans to replace
all its remaining diesel-electric trains with hydrogen trains by 2035. In the United Kingdom, Alstom
announced in 2018 their plan to retrofit British Rail Class 321 trainsets with fuel cells.
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A phasor measurement unit (PMU) is a device used to
estimate the magnitude and phase angle of an electrical phasor quantity (such as voltage or current) in
the electricity grid using a common time source for synchronization. Time synchronization is usually
provided by GPS or IEEE 1588 Precision Time Protocol, which allows synchronized real-time
measurements of multiple remote points on the grid. PMUs are capable of capturing samples from a
waveform in quick succession and reconstructing the phasor quantity, made up of an angle
measurement and a magnitude measurement. The resulting measurement is known as a synchrophasor.
These time synchronized measurements are important because if the grid’s supply and demand are not
perfectly matched, frequency imbalances can cause stress on the grid, which is a potential cause for
power outages.
PMUs can also be used to measure the frequency in the power grid. A
typical commercial PMU can report measurements with very high temporal resolution, up to 120
measurements per second. This helps engineers in analyzing dynamic events in the grid which is not
possible with traditional SCADA measurements that generate one measurement every 2 or 4 seconds.
Therefore, PMUs equip utilities with enhanced monitoring and control capabilities and are considered to
be one of the most important measuring devices in the future of power systems. A PMU can be a
dedicated device, or the PMU function can be incorporated into a protective relay or other device.
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In 1893, Charles Proteus Steinmetz presented a paper on
simplified mathematical description of the waveforms of alternating current electricity. Steinmetz called
his representation a phasor. With the invention of phasor measurement units (PMU) in 1988 by Dr. Arun
G. Phadke and Dr. James S. Thorp at Virginia Tech, Steinmetz’s technique of phasor calculation evolved
into the calculation of real time phasor measurements that are synchronized to an absolute time
reference provided by the Global Positioning System. We therefore refer to synchronized phasor
measurements as synchrophasors. Early prototypes of the PMU were built at Virginia Tech, and
Macrodyne built the first PMU (model 1690) in 1992. Today they are available commercially.
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With the increasing growth of distributed energy resources on
the power grid, more observability and control systems will be needed to accurately monitor power
flow. Historically, power has been delivered in a uni-directional fashion through passive components to
customers, but now that customers can generate their own power with technologies such as solar PV,
this is changing into a bidirectional system for distribution systems. With this change it is imperative that
transmission and distribution networks are continuously being observed through advanced sensor
technology, such as ––PMUs and uPMUs.