The history of electromagnetic theory begins with ancient measures to
understand atmospheric electricity, in particular lightning. People
then had little understanding of electricity, and were unable to
explain the phenomena. Scientific understanding into the nature of
electricity grew throughout the eighteenth and nineteenth centuries
through the work of researchers such as Ampère, Coulomb, Faraday and
In the 19th century it had become clear that electricity and magnetism
were related, and their theories were unified: wherever charges are in
motion electric current results, and magnetism is due to electric
current. The source for electric field is electric charge, whereas
that for magnetic field is electric current (charges in motion).
1 Ancient and classical history
2 Middle Ages and the Renaissance
3 18th century
3.1 Improving the electric machine
3.2 Electrics and non-electrics
3.3 Vitreous and resinous
3.4 Leyden jar
3.5 Late 18th century
4 19th century
4.1 Early 19th century
4.2 Faraday and Henry
4.3 Middle 19th century
4.5 End of the 19th century
4.6 Second Industrial Revolution
5 20th century
5.1 Lorentz and Poincaré
5.2 Einstein's Annus Mirabilis
5.3 Mid-20th century
5.4 Parity violation
5.5 Electroweak theory
5.6 Electrodynamic tethers
6 21st century
6.1 Electromagnetic technologies
6.2 Unified theories
6.3 Open problems
7 See also
Ancient and classical history
The knowledge of static electricity dates back to the earliest
civilizations, but for millennia it remained merely an interesting and
mystifying phenomenon, without a theory to explain its behavior and
often confused with magnetism. The ancients were acquainted with
rather curious properties possessed by two minerals, amber (Greek:
ἤλεκτρον, ēlektron) and magnetic iron ore (μαγνῆτις
λίθος magnētis lithos, "the Magnesian stone, lodestone").
Amber, when rubbed, attracts lightweight objects, such as feathers;
magnetic iron ore has the power of attracting iron.
The discovery of the property of magnets.
Magnets were first found in a natural state; certain iron oxides were
discovered in various parts of the world, notably in Magnesia in Asia
Minor, that had the property of attracting small pieces of iron, which
is shown here.
Based on his find of an
Olmec hematite artifact in Central America,
the American astronomer John Carlson has suggested that "the
have discovered and used the geomagnetic lodestone compass earlier
than 1000 BC". If true, this "predates the Chinese discovery of the
geomagnetic lodestone compass by more than a millennium".
Carlson speculates that the Olmecs may have used similar artifacts as
a directional device for astrological or geomantic purposes, or to
orient their temples, the dwellings of the living or the interments of
the dead. The earliest
Chinese literature reference to magnetism lies
in a 4th-century BC book called Book of the Devil Valley Master
(鬼谷子): "The lodestone makes iron come or it attracts it."
Electric catfish are found in tropical Africa and the
Long before any knowledge of electromagnetism existed, people were
aware of the effects of electricity.
Lightning and other
manifestations of electricity such as
St. Elmo's fire
St. Elmo's fire were known in
ancient times, but it was not understood that these phenomena had a
common origin. Ancient
Egyptians were aware of shocks when
interacting with electric fish (such as the electric catfish) or other
animals (such as electric eels). The shocks from animals were
apparent to observers since pre-history by a variety of peoples that
came into contact with them. Texts from 2750 BC by the ancient
Egyptians referred to these fish as "thunderer of the Nile" and saw
them as the "protectors" of all the other fish. Another possible
approach to the discovery of the identity of lightning and electricity
from any other source, is to be attributed to the Arabs, who before
the 15th century used the same Arabic word for lightning (barq) and
the electric ray.
Thales of Miletus, writing at around 600 BC, noted that rubbing fur on
various substances such as amber would cause them to attract specks of
dust and other light objects.
Thales wrote on the effect now known
as static electricity. The Greeks noted that if they rubbed the amber
for long enough they could even get an electric spark to jump.
The electrostatic phenomena was again reported millennia later by
Roman and Arabic naturalists and physicians. Several ancient
writers, such as
Pliny the Elder
Pliny the Elder and Scribonius Largus, attested to
the numbing effect of electric shocks delivered by catfish and torpedo
rays. Pliny in his books writes: "The ancient Tuscans by their
learning hold that there are nine gods that send forth lightning and
those of eleven sorts." This was in general the early pagan idea of
lightning. The ancients held some concept that 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.
A number of objects found in
Iraq in 1938 dated to the early centuries
AD (Sassanid Mesopotamia), called the Baghdad Battery, resembles a
galvanic cell and is believed by some to have been used for
electroplating. The claims are controversial because of supporting
evidence and theories for the uses of the artifacts, physical
evidence on the objects conducive for electrical functions, and if
they were electrical in nature. As a result, the nature of these
objects is based on speculation, and the function of these artifacts
remains in doubt.
Middle Ages and the Renaissance
Magnetic attraction was once accounted for by
the working of a soul in the stone.
Shen Kuo wrote
Dream Pool Essays
Dream Pool Essays (夢溪筆談); Shen also first
described the magnetic needle.
In the 11th century, the Chinese scientist
Shen Kuo (1031–1095) was
the first person to write of the magnetic needle compass and that it
improved the accuracy of navigation by employing the astronomical
concept of true north (Dream Pool Essays, AD 1088 ), and by the 12th
century the Chinese were known to use the lodestone compass for
navigation. In 1187,
Alexander Neckam was the first in Europe to
describe the compass and its use for navigation.
In the thirteenth century Peter Peregrinus, a native of Maricourt in
Picardy, made a discovery of fundamental importance. The French
13th century scholar conducted experiments on magnetism and wrote the
first extant treatise describing the properties of magnets and
pivoting compass needles. The dry compass was invented around 1300
by Italian inventor Flavio Gioja.
Archbishop Eustathius of Thessalonica, Greek scholar and writer of the
12th century, records that Woliver, king of the Goths, was able to
draw sparks from his body. The same writer states that a certain
philosopher was able while dressing to draw sparks from his clothes, a
result seemingly akin to that obtained by
Robert Symmer in his silk
stocking experiments, a careful account of which may be found in the
'Philosophical Transactions,' 1759.
Gerolamo Cardano wrote about electricity in De
Subtilitate (1550) distinguishing, perhaps for the first time, between
electrical and magnetic forces.
Toward the late 16th century, a physician of Queen Elizabeth's time,
Dr. William Gilbert, in De Magnete, expanded on Cardano's work and
New Latin word electricus from ἤλεκτρον
(ēlektron), the Greek word for "amber". Gilbert, a native of
Colchester, Fellow of St John's College, Cambridge, and sometime
President of the College of Physicians, was one of the earliest and
most distinguished English men of science — a man whose work Galileo
thought enviably great. He was appointed Court physician, and a
pension was settled on him to set him free to continue his researches
in Physics and Chemistry.
Gilbert undertook a number of careful electrical experiments, in the
course of which he discovered that many substances other than amber,
such as sulphur, wax, glass, etc., were capable of manifesting
electrical properties. Gilbert also discovered that a heated body lost
its electricity and that moisture prevented the electrification of all
bodies, due to the now well-known fact that moisture impaired the
insulation of such bodies. He also noticed that electrified substances
attracted all other substances indiscriminately, whereas a magnet only
attracted iron. The many discoveries of this nature earned for Gilbert
the title of founder of the electrical science. By investigating
the forces on a light metallic needle, balanced on a point, he
extended the list of electric bodies, and found also that many
substances, including metals and natural magnets, showed no attractive
forces when rubbed. He noticed that dry weather with north or east
wind was the most favourable atmospheric condition for exhibiting
electric phenomena—an observation liable to misconception until the
difference between conductor and insulator was understood.
Gilbert's work was followed up by
Robert Boyle (1627–1691), the
famous natural philosopher who was once described as "father of
Chemistry, and uncle of the Earl of Cork." Boyle was one of the
founders of the Royal Society when it met privately in Oxford, and
became a member of the Council after the Society was incorporated by
Charles II. in 1663. He worked frequently at the new science of
electricity, and added several substances to Gilbert's list of
electrics. He left a detailed account of his researches under the
title of Experiments on the Origin of Electricity. Boyle, in 1675,
stated that electric attraction and repulsion can act across a vacuum.
One of his important discoveries was that electrified bodies in a
vacuum would attract light substances, thus indicating that the
electrical effect did not depend upon the air as a medium. He also
added resin to the then known list of electrics.
This was followed in 1660 by Otto von Guericke, who invented an early
electrostatic generator. By the end of the 17th Century, researchers
had developed practical means of generating electricity by friction
with an electrostatic generator, but the development of electrostatic
machines did not begin in earnest until the 18th century, when they
became fundamental instruments in the studies about the new science of
The first usage of the word electricity is ascribed to Sir Thomas
Browne in his 1646 work, Pseudodoxia Epidemica.
The first appearance of the term electromagnetism on the other hand
comes from an earlier date: 1641. Magnes, by the Jesuit luminary
Athanasius Kircher, carries on page 640 the provocative
chapter-heading: "Elektro-magnetismos i.e. On the
Magnetism of amber,
or electrical attractions and their causes"
(ηλεκτρο-μαγνητισμος id est sive De Magnetismo
electri, seu electricis attractionibus earumque causis).
Improving the electric machine
Main article: electrostatic machine
Generator built by Francis Hauksbee.
The electric machine was subsequently improved by Francis Hauksbee,
his student Litzendorf, and by Prof. Georg Matthias Bose, about 1750.
Litzendorf, researching for Christian August Hausen, substituted a
glass ball for the sulphur ball of Guericke. Bose was the first to
employ the "prime conductor" in such machines, this consisting of an
iron rod held in the hand of a person whose body was insulated by
standing on a block of resin. Ingenhousz, during 1746, invented
electric machines made of plate glass. Experiments with the
electric machine were largely aided by the discovery that a glass
plate, coated on both sides with tinfoil, would accumulate electric
charge when connected with a source of electromotive force. The
electric machine was soon further improved by Andrew Gordon, a
Scotsman, Professor at Erfurt, who substituted a glass cylinder in
place of a glass globe; and by Giessing of Leipzig who added a
"rubber" consisting of a cushion of woollen material. The collector,
consisting of a series of metal points, was added to the machine by
Benjamin Wilson about 1746, and in 1762,
John Canton of England (also
the inventor of the first pith-ball electroscope) improved the
efficiency of electric machines by sprinkling an amalgam of tin over
the surface of the rubber.
Electrics and non-electrics
In 1729, Stephen Gray conducted a series of experiments that
demonstrated the difference between conductors and non-conductors
(insulators), showing amongst other things that a metal wire and even
pack thread conducted electricity, whereas silk did not. In one of his
experiments he sent an electric current through 800 feet of hempen
thread which was suspended at intervals by loops of silk thread. When
he tried to conduct the same experiment substituting the silk for
finely spun brass wire, he found that the electric current was no
longer carried throughout the hemp cord, but instead seemed to vanish
into the brass wire. From this experiment he classified substances
into two categories: "electrics" like glass, resin and silk and
"non-electrics" like metal and water. "Non-electrics" conducted
charges while "electrics" held the charge.
Vitreous and resinous
Intrigued by Gray's results, in 1732, C. F. du Fay began to conduct
several experiments. In his first experiment, Du Fay concluded that
all objects except metals, animals, and liquids could be electrified
by rubbing and that metals, animals and liquids could be electrified
by means of an electric machine, thus discrediting Gray's "electrics"
and "non-electrics" classification of substances.
In 1737 Du Fay and Hauksbee independently discovered what they
believed to be two kinds of frictional electricity; one generated from
rubbing glass, the other from rubbing resin. From this, Du Fay
theorized that electricity consists of two electrical fluids,
"vitreous" and "resinous", that are separated by friction and that
neutralize each other when combined. This picture of electricity
was also supported by
Christian Gottlieb Kratzenstein
Christian Gottlieb Kratzenstein in his
theoretical and experimental works. The two-fluid theory would later
give rise to the concept of positive and negative electrical charges
devised by Benjamin Franklin.
Pieter van Musschenbroek.
The Leyden jar, a type of capacitor for electrical energy in large
quantities, was invented independently by
Ewald Georg von Kleist
Ewald Georg von Kleist on 11
October 1744 and by
Pieter van Musschenbroek
Pieter van Musschenbroek in 1745—1746 at Leiden
University (the latter location giving the device its name).
William Watson, when experimenting with the Leyden jar, discovered in
1747 that a discharge of static electricity was equivalent to an
Capacitance was first observed by Von Kleist of
Leyden in 1754. Von Kleist happened to hold, near his electric
machine, a small bottle, in the neck of which there was an iron nail.
Touching the iron nail accidentally with his other hand he received a
severe electric shock. In much the same way Musschenbroeck assisted by
Cunaens received a more severe shock from a somewhat similar glass
bottle. Sir William Watson of England greatly improved this device, by
covering the bottle, or jar, outside and in with tinfoil. This piece
of electrical apparatus will be easily recognized as the well-known
Leyden jar, so called by the Abbot Nollet of Paris, after the place of
In 1741, John Ellicott "proposed to measure the strength of
electrification by its power to raise a weight in one scale of a
balance while the other was held over the electrified body and pulled
to it by its attractive power". As early as 1746, Jean-Antoine Nollet
(1700–1770) had performed experiments on the propagation speed of
electricity. By involving 200 monks connected from hand to hand by a
7-m iron wire so as to form a circle of about 1.6 km, he was able
to prove that this speed is finite, even though very high. In
1749, Sir William Watson conducted numerous experiments to ascertain
the velocity of electricity in a wire. These experiments, although
perhaps not so intended, also demonstrated the possibility of
transmitting signals to a distance by electricity. In these
experiments, the signal appeared to travel the 12,276-foot length of
the insulated wire instantaneously. Le Monnier in France had
previously made somewhat similar experiments, sending shocks through
an iron wire 1,319 feet long.
About 1750, first experiments in electrotherapy were made. Various
experimenters made tests to ascertain the physiological and
therapeutical effects of electricity. Typical for this effort was
Kratzenstein in Halle who in 1744 wrote a treatise on the subject.
Demainbray in Edinburgh examined the effects of electricity upon
plants and concluded that the growth of two myrtle trees was quickened
by electrification. These myrtles were electrified "during the whole
month of October, 1746, and they put forth branches and blossoms
sooner than other shrubs of the same kind not electrified.". Abbé
Ménon in France tried the effects of a continued application of
electricity upon men and birds and found that the subjects
experimented on lost weight, thus apparently showing that electricity
quickened the excretions. The efficacy of electric shocks in
cases of paralysis was tested in the county hospital at Shrewsbury,
England, with rather poor success.
Late 18th century
Benjamin Franklin promoted his investigations of electricity and
theories through the famous, though extremely dangerous, experiment of
having his son fly a kite through a storm-threatened sky. A key
attached to the kite string sparked and charged a Leyden jar, thus
establishing the link between lightning and electricity. Following
these experiments, he invented a lightning rod. It is either Franklin
(more frequently) or
Ebenezer Kinnersley of
frequently) who is considered to have established the convention of
positive and negative electricity.
Theories regarding the nature of electricity were quite vague at this
period, and those prevalent were more or less conflicting. Franklin
considered that electricity was an imponderable fluid pervading
everything, and which, in its normal condition, was uniformly
distributed in all substances. He assumed that the electrical
manifestations obtained by rubbing glass were due to the production of
an excess of the electric fluid in that substance and that the
manifestations produced by rubbing wax were due to a deficit of the
fluid. This explanation was opposed by supporters of the "two-fluid"
Robert Symmer in 1759. In this theory, the vitreous and
resinous electricities were regarded as imponderable fluids, each
fluid being composed of mutually repellent particles while the
particles of the opposite electricities are mutually attractive. When
the two fluids unite as a result of their attraction for one another,
their effect upon external objects is neutralized. The act of rubbing
a body decomposes the fluids, one of which remains in excess on the
body and manifests itself as vitreous or resinous electricity.
Up to the time of Franklin's historic kite experiment, the
identity of the electricity developed by rubbing and by electrostatic
machines (frictional electricity) with lightning had not been
generally established. Dr. Wall, Abbot Nollet, Hauksbee,
Stephen Gray and John Henry Winkler had indeed suggested the
resemblance between the phenomena of "electricity" and "lightning",
Gray having intimated that they only differed in degree. It was
doubtless Franklin, however, who first proposed tests to determine the
sameness of the phenomena. In a letter to Peter Comlinson of London,
on 19 October 1752, Franklin, referring to his kite experiment, wrote,
"At this key the phial (Leyden jar) may be charged; and from the
electric fire thus obtained spirits may be kindled, and all the other
electric experiments be formed which are usually done by the help of a
rubbed glass globe or tube, and thereby the sameness of the electric
matter with that of lightning be completely demonstrated."
On 10 May 1742 Thomas-François Dalibard, at Marley (near Paris),
using a vertical iron rod 40 feet long, obtained results corresponding
to those recorded by Franklin and somewhat prior to the date of
Franklin's experiment. Franklin's important demonstration of the
sameness of frictional electricity and lightning doubtless added zest
to the efforts of the many experimenters in this field in the last
half of the 18th century, to advance the progress of the science.
Franklin's observations aided later scientists such
as Michael Faraday, Luigi Galvani, Alessandro Volta, André-Marie
Ampère and Georg Simon Ohm, whose collective work provided the basis
for modern electrical technology and for whom fundamental units of
electrical measurement are named. Others who would advance the field
of knowledge included William Watson, Georg Matthias Bose, Smeaton,
Louis-Guillaume Le Monnier, Jacques de Romas, Jean Jallabert, Giovanni
Battista Beccaria, Tiberius Cavallo, John Canton, Robert Symmer, Abbot
Nollet, John Henry Winkler, Benjamin Wilson, Ebenezer Kinnersley,
Joseph Priestley, Franz Aepinus, Edward Hussey Délavai, Henry
Cavendish, and Charles-Augustin de Coulomb. Descriptions of many of
the experiments and discoveries of these early electrical scientists
may be found in the scientific publications of the time, notably the
Philosophical Transactions, Philosophical Magazine, Cambridge
Mathematical Journal, Young's Natural Philosophy, Priestley's History
of Electricity, Franklin's Experiments and Observations on
Electricity, Cavalli's Treatise on
Electricity and De la Rive's
Treatise on Electricity.
Henry Elles was one of the first people to suggest links between
electricity and magnetism. In 1757 he claimed that he had written to
the Royal Society in 1755 about the links between electricity and
magnetism, asserting that "there are some things in the power of
magnetism very similar to those of electricity" but he did "not by any
means think them the same". In 1760 he similarly claimed that in 1750
he had been the first "to think how the electric fire may be the cause
of thunder". Among the more important of the electrical research
and experiments during this period were those of Franz Aepinus, a
noted German scholar (1724–1802) and
Henry Cavendish of London,
Franz Aepinus is credited as the first to conceive of the view of the
reciprocal relationship of electricity and magnetism. In his work
Tentamen Theoria Electricitatis et Magnetism, published in Saint
Petersburg in 1759, he gives the following amplification of Franklin's
theory, which in some of its features is measurably in accord with
present-day views: "The particles of the electric fluid repel each
other, attract and are attracted by the particles of all bodies with a
force that decreases in proportion as the distance increases; the
electric fluid exists in the pores of bodies; it moves unobstructedly
through non-electric (conductors), but moves with difficulty in
insulators; the manifestations of electricity are due to the unequal
distribution of the fluid in a body, or to the approach of bodies
unequally charged with the fluid." Aepinus formulated a corresponding
theory of magnetism excepting that, in the case of magnetic phenomena,
the fluids only acted on the particles of iron. He also made numerous
electrical experiments apparently showing that, in order to manifest
electrical effects, tourmaline must be heated to between 37.5°С and
100 °C. In fact, tourmaline remains unelectrified when its
temperature is uniform, but manifests electrical properties when its
temperature is rising or falling. Crystals that manifest electrical
properties in this way are termed pyroelectric; along with tourmaline,
these include sulphate of quinine and quartz.
Henry Cavendish independently conceived a theory of electricity nearly
akin to that of Aepinus. In 1784, he was perhaps the first to
utilize an electric spark to produce an explosion of hydrogen and
oxygen in the proper proportions that would create pure water.
Cavendish also discovered the inductive capacity of dielectrics
(insulators), and, as early as 1778, measured the specific inductive
capacity for beeswax and other substances by comparison with an air
Drawing of Coulomb's torsion balance. From Plate 13 of his 1785
Around 1784 C. A. Coulomb devised the torsion balance, discovering
what is now known as Coulomb's law: the force exerted between two
small electrified bodies varies inversely as the square of the
distance, not as Aepinus in his theory of electricity had assumed,
merely inversely as the distance. According to the theory advanced by
Cavendish, "the particles attract and are attracted inversely as some
less power of the distance than the cube." A large part of the
domain of electricity became virtually annexed by Coulomb's discovery
of the law of inverse squares.
Through the experiments of William Watson and others proving that
electricity could be transmitted to a distance, the idea of making
practical use of this phenomenon began, around 1753, to engross the
minds of inquisitive people. To this end, suggestions as to the
employment of electricity in the transmission of intelligence were
made. The first of the methods devised for this purpose was probably
that of Georges Lesage in 1774. This method consisted of
24 wires, insulated from one another and each having had a pith ball
connected to its distant end. Each wire represented a letter of the
alphabet. To send a message, a desired wire was charged momentarily
with electricity from an electric machine, whereupon the pith ball
connected to that wire would fly out. Other methods of telegraphing in
which frictional electricity was employed were also tried, some of
which are described in the history on the telegraph.
The era of galvanic or voltaic electricity represented a revolutionary
break from the historical focus on frictional electricity. Alessandro
Volta discovered that chemical reactions could be used to create
positively charged anodes and negatively charged cathodes. When a
conductor was attached between these, the difference in the electrical
potential (also known as voltage) drove a current between them through
the conductor. The potential difference between two points is measured
in units of volts in recognition of Volta's work.
The first mention of voltaic electricity, although not recognized as
such at the time, was probably made by
Johann Georg Sulzer
Johann Georg Sulzer in 1767,
who, upon placing a small disc of zinc under his tongue and a small
disc of copper over it, observed a peculiar taste when the respective
metals touched at their edges. Sulzer assumed that when the metals
came together they were set into vibration, acting upon the nerves of
the tongue to produce the effects noticed. In 1790, Prof. Luigi
Alyisio Galvani of Bologna, while conducting experiments on "animal
electricity", noticed the twitching of a frog's legs in the presence
of an electric machine. He observed that a frog's muscle, suspended on
an iron balustrade by a copper hook passing through its dorsal column,
underwent lively convulsions without any extraneous cause, the
electric machine being at this time absent.
To account for this phenomenon, Galvani assumed that electricity of
opposite kinds existed in the nerves and muscles of the frog, the
muscles and nerves constituting the charged coatings of a Leyden jar.
Galvani published the results of his discoveries, together with his
hypothesis, which engrossed the attention of the physicists of that
time. The most prominent of these was Volta, professor of physics
at Pavia, who contended that the results observed by Galvani were the
result of the two metals, copper and iron, acting as electromotors,
and that the muscles of the frog played the part of a conductor,
completing the circuit. This precipitated a long discussion between
the adherents of the conflicting views. One group agreed with Volta
that the electric current was the result of an electromotive force of
contact at the two metals; the other adopted a modification of
Galvani's view and asserted that the current was the result of a
chemical affinity between the metals and the acids in the pile.
Michael Faraday wrote in the preface to his Experimental Researches,
relative to the question of whether metallic contact is productive of
a part of the electricity of the voltaic pile: "I see no reason as yet
to alter the opinion I have given; ... but the point itself is of such
great importance that I intend at the first opportunity renewing the
inquiry, and, if I can, rendering the proofs either on the one side or
the other, undeniable to all."
Even Faraday himself, however, did not settle the controversy, and
while the views of the advocates on both sides of the question have
undergone modifications, as subsequent investigations and discoveries
demanded, up to 1918 diversity of opinion on these points continued to
crop out. Volta made numerous experiments in support of his theory and
ultimately developed the pile or battery, which was the precursor
of all subsequent chemical batteries, and possessed the distinguishing
merit of being the first means by which a prolonged continuous current
of electricity was obtainable. Volta communicated a description of his
pile to the
Royal Society of London
Royal Society of London and shortly thereafter Nicholson
and Cavendish (1780) produced the decomposition of water by means of
the electric current, using Volta's pile as the source of
Early 19th century
Alessandro Volta constructed the first device to produce a
large electric current, later known as the electric battery. Napoleon,
informed of his works, summoned him in 1801 for a command performance
of his experiments. He received many medals and decorations, including
the Légion d'honneur.
Davy in 1806, employing a voltaic pile of approximately 250 cells, or
couples, decomposed potash and soda, showing that these substances
were respectively the oxides of potassium and sodium, metals which
previously had been unknown. These experiments were the beginning of
electrochemistry, the investigation of which Faraday took up, and
concerning which in 1833 he announced his important law of
electrochemical equivalents, viz.: "The same quantity of electricity
— that is, the same electric current — decomposes chemically
equivalent quantities of all the bodies which it traverses; hence the
weights of elements separated in these electrolytes are to each other
as their chemical equivalents." Employing a battery of 2,000 elements
of a voltaic pile
Humphry Davy in 1809 gave the first public
demonstration of the electric arc light, using for the purpose
charcoal enclosed in a vacuum.
Somewhat important to note, it was not until many years after the
discovery of the voltaic pile that the sameness of animal and
frictional electricity with voltaic electricity was clearly recognized
and demonstrated. Thus as late as January 1833 we find Faraday
writing in a paper on the electricity of the electric ray. "After
an examination of the experiments of Walsh, Ingenhousz, Henry
Cavendish, Sir H. Davy, and Dr. Davy, no doubt remains on my mind as
to the identity of the electricity of the torpedo with common
(frictional) and voltaic electricity; and I presume that so little
will remain on the mind of others as to justify my refraining from
entering at length into the philosophical proof of that identity. The
doubts raised by Sir
Humphry Davy have been removed by his brother,
Dr. Davy; the results of the latter being the reverse of those of the
former. ... The general conclusion which must, I think, be drawn from
this collection of facts (a table showing the similarity, of
properties of the diversely named electricities) is, that electricity,
whatever may be its source, is identical in its nature."
It is proper to state, however, that prior to Faraday's time the
similarity of electricity derived from different sources was more than
suspected. Thus, William Hyde Wollaston, wrote in 1801: "This
similarity in the means by which both electricity and galvanism
(voltaic electricity) appear to be excited in addition to the
resemblance that has been traced between their effects shows that they
are both essentially the same and confirm an opinion that has already
been advanced by others, that all the differences discoverable in the
effects of the latter may be owing to its being less intense, but
produced in much larger quantity." In the same paper Wollaston
describes certain experiments in which he uses very fine wire in a
solution of sulphate of copper through which he passed electric
currents from an electric machine. This is interesting in connection
with the later day use of almost similarly arranged fine wires in
electrolytic receivers in wireless, or radio-telegraphy.
Hans Christian Ørsted.
In the first half of the 19th century many very important additions
were made to the world's knowledge concerning electricity and
magnetism. For example, in 1819
Hans Christian Ørsted
Hans Christian Ørsted of Copenhagen
discovered the deflecting effect of an electric current traversing a
wire upon- a suspended magnetic needle.
This discovery gave a clue to the subsequently proved intimate
relationship between electricity and magnetism which was promptly
followed up by Ampère who shortly thereafter (1821) announced his
celebrated theory of electrodynamics, relating to the force that one
current exerts upon another, by its electro-magnetic effects,
Two parallel portions of a circuit attract one another if the currents
in them are flowing in the same direction, and repel one another if
the currents flow in the opposite direction.
Two portions of circuits crossing one another obliquely attract one
another if both the currents flow either towards or from the point of
crossing, and repel one another if one flows to and the other from
When an element of a circuit exerts a force on another element of a
circuit, that force always tends to urge the second one in a direction
at right angles to its own direction.
Ampere brought a multitude of phenomena into theory by his
investigations of the mechanical forces between conductors supporting
currents and magnets.
The German physicist Seebeck discovered in 1821 that when heat is
applied to the junction of two metals that had been soldered together
an electric current is set up. This is termed thermoelectricity.
Seebeck's device consists of a strip of copper bent at each end and
soldered to a plate of bismuth. A magnetic needle is placed parallel
with the copper strip. When the heat of a lamp is applied to the
junction of the copper and bismuth an electric current is set up which
deflects the needle.
Around this time,
Siméon Denis Poisson
Siméon Denis Poisson attacked the difficult problem
of induced magnetization, and his results, though differently
expressed, are still the theory, as a most important first
approximation. It was in the application of mathematics to physics
that his services to science were performed. Perhaps the most
original, and certainly the most permanent in their influence, were
his memoirs on the theory of electricity and magnetism, which
virtually created a new branch of mathematical physics.
George Green wrote An Essay on the Application of Mathematical
Analysis to the Theories of
Magnetism in 1828. The
essay introduced several important concepts, among them a theorem
similar to the modern Green's theorem, the idea of potential functions
as currently used in physics, and the concept of what are now called
Green's functions. George Green was the first person to create a
mathematical theory of electricity and magnetism and his theory formed
the foundation for the work of other scientists such as James Clerk
Maxwell, William Thomson, and others.
Peltier in 1834 discovered an effect opposite to thermoelectricity,
namely, that when a current is passed through a couple of dissimilar
metals the temperature is lowered or raised at the junction of the
metals, depending on the direction of the current. This is termed the
Peltier effect. The variations of temperature are found to be
proportional to the strength of the current and not to the square of
the strength of the current as in the case of heat due to the ordinary
resistance of a conductor. This second law is the I2R law, discovered
experimentally in 1841 by the English physicist Joule. In other words,
this important law is that the heat generated in any part of an
electric circuit is directly proportional to the product of the
resistance R of this part of the circuit and to the square of the
strength of current I flowing in the circuit.
In 1822 Johann Schweigger devised the first galvanometer. This
instrument was subsequently much improved by Wilhelm Weber (1833). In
William Sturgeon of Woolwich, England, invented the horseshoe and
straight bar electromagnet, receiving therefor the silver medal of the
Society of Arts. In 1837
Carl Friedrich Gauss
Carl Friedrich Gauss and Weber (both
noted workers of this period) jointly invented a reflecting
galvanometer for telegraph purposes. This was the forerunner of the
Thomson reflecting and other exceedingly sensitive galvanometers once
used in submarine signaling and still widely employed in electrical
measurements. Arago in 1824 made the important discovery that when a
copper disc is rotated in its own plane, and if a magnetic needle be
freely suspended on a pivot over the disc, the needle will rotate with
the disc. If on the other hand the needle is fixed it will tend to
retard the motion of the disc. This effect was termed Arago's
Georg Simon Ohm.
Futile attempts were made by Charles Babbage, Peter Barlow, John
Herschel and others to explain this phenomenon. The true explanation
was reserved for Faraday, namely, that electric currents are induced
in the copper disc by the cutting of the magnetic lines of force of
the needle, which currents in turn react on the needle. Georg Simon
Ohm did his work on resistance in the years 1825 and 1826, and
published his results in 1827 as the book Die galvanische Kette,
mathematisch bearbeitet. He drew considerable inspiration from
Fourier's work on heat conduction in the theoretical explanation of
his work. For experiments, he initially used voltaic piles, but later
used a thermocouple as this provided a more stable voltage source in
terms of internal resistance and constant potential difference. He
used a galvanometer to measure current, and knew that the voltage
between the thermocouple terminals was proportional to the junction
temperature. He then added test wires of varying length, diameter, and
material to complete the circuit. He found that his data could be
modeled through a simple equation with variable composed of the
reading from a galvanometer, the length of the test conductor,
thermocouple junction temperature, and a constant of the entire setup.
From this, Ohm determined his law of proportionality and published his
results. In 1827, he announced the now famous law that bears his name,
Electromotive force = Current × Resistance
Ohm brought into order a host of puzzling facts connecting
electromotive force and electric current in conductors, which all
previous electricians had only succeeded in loosely binding together
qualitatively under some rather vague statements. Ohm found that the
results could be summed up in such a simple law and by Ohm's discovery
a large part of the domain of electricity became annexed to theory.
Faraday and Henry
The discovery of electromagnetic induction was made almost
simultaneously, although independently, by Michael Faraday, who was
first to make the discovery in 1831, and
Joseph Henry in 1832.
Henry's discovery of self-induction and his work on spiral conductors
using a copper coil were made public in 1835, just before those of
In 1831 began the epoch-making researches of Michael Faraday, the
famous pupil and successor of
Humphry Davy at the head of the Royal
Institution, London, relating to electric and electromagnetic
induction. The remarkable researches of Faraday, the prince of
experimentalists, on electrostatics and electrodynamics and the
induction of currents. These were rather long in being brought from
the crude experimental state to a compact system, expressing the real
essence. Faraday was not a competent mathematician, but
had he been one, he would have been greatly assisted in his
researches, have saved himself much useless speculation, and would
have anticipated much later work. He would, for instance, knowing
Ampere's theory, by his own results have readily been led to Neumann's
theory, and the connected work of
Helmholtz and Thomson. Faraday's
studies and researches extended from 1831 to 1855 and a detailed
description of his experiments, deductions and speculations are to be
found in his compiled papers, entitled Experimental Researches in
Electricity.' Faraday was by profession a chemist. He was not in the
remotest degree a mathematician in the ordinary sense — indeed it is
a question if in all his writings there is a single mathematical
The experiment which led Faraday to the discovery of electromagnetic
induction was made as follows: He constructed what is now and was then
termed an induction coil, the primary and secondary wires of which
were wound on a wooden bobbin, side by side, and insulated from one
another. In the circuit of the primary wire he placed a battery of
approximately 100 cells. In the secondary wire he inserted a
galvanometer. On making his first test he observed no results, the
galvanometer remaining quiescent, but on increasing the length of the
wires he noticed a deflection of the galvanometer in the secondary
wire when the circuit of the primary wire was made and broken. This
was the first observed instance of the development of electromotive
force by electromagnetic induction.
He also discovered that induced currents are established in a second
closed circuit when the current strength is varied in the first wire,
and that the direction of the current in the secondary circuit is
opposite to that in the first circuit. Also that a current is induced
in a secondary circuit when another circuit carrying a current is
moved to and from the first circuit, and that the approach or
withdrawal of a magnet to or from a closed circuit induces momentary
currents in the latter. In short, within the space of a few months
Faraday discovered by experiment virtually all the laws and facts now
known concerning electro-magnetic induction and magneto-electric
induction. Upon these discoveries, with scarcely an exception, depends
the operation of the telephone, the dynamo machine, and incidental to
the dynamo electric machine practically all the gigantic electrical
industries of the world, including electric lighting, electric
traction, the operation of electric motors for power purposes, and
electro-plating, electrotyping, etc.
In his investigations of the peculiar manner in which iron filings
arrange themselves on a cardboard or glass in proximity to the poles
of a magnet, Faraday conceived the idea of magnetic "lines of force"
extending from pole to pole of the magnet and along which the filings
tend to place themselves. On the discovery being made that magnetic
effects accompany the passage of an electric current in a wire, it was
also assumed that similar magnetic lines of force whirled around the
wire. For convenience and to account for induced electricity it was
then assumed that when these lines of force are "cut" by a wire in
passing across them or when the lines of force in rising and falling
cut the wire, a current of electricity is developed, or to be more
exact, an electromotive force is developed in the wire that sets up a
current in a closed circuit. Faraday advanced what has been termed the
molecular theory of electricity which assumes that electricity is
the manifestation of a peculiar condition of the molecule of the body
rubbed or the ether surrounding the body. Faraday also, by experiment,
discovered paramagnetism and diamagnetism, namely, that all solids and
liquids are either attracted or repelled by a magnet. For example,
iron, nickel, cobalt, manganese, chromium, etc., are paramagnetic
(attracted by magnetism), whilst other substances, such as bismuth,
phosphorus, antimony, zinc, etc., are repelled by magnetism or are
Brugans of Leyden in 1778 and Le Baillif and Becquerel in 1827 had
previously discovered diamagnetism in the case of bismuth and
antimony. Faraday also rediscovered specific inductive capacity in
1837, the results of the experiments by Cavendish not having been
published at that time. He also predicted the retardation of
signals on long submarine cables due to the inductive effect of the
insulation of the cable, in other words, the static capacity of the
cable. In 1816 telegraph pioneer
Francis Ronalds had also observed
signal retardation on his buried telegraph lines, attributing it to
The 25 years immediately following Faraday's discoveries of
electromagnetic induction were fruitful in the promulgation of laws
and facts relating to induced currents and to magnetism. In 1834
Heinrich Lenz and
Moritz von Jacobi
Moritz von Jacobi independently demonstrated the now
familiar fact that the currents induced in a coil are proportional to
the number of turns in the coil. Lenz also announced at that time his
important law that, in all cases of electromagnetic induction the
induced currents have such a direction that their reaction tends to
stop the motion that produces them, a law that was perhaps deducible
from Faraday's explanation of Arago's rotations.
The induction coil was first designed by
Nicholas Callan in 1836. In
1845 Joseph Henry, the American physicist, published an account of his
valuable and interesting experiments with induced currents of a high
order, showing that currents could be induced from the secondary of an
induction coil to the primary of a second coil, thence to its
secondary wire, and so on to the primary of a third coil, etc.
Heinrich Daniel Ruhmkorff
Heinrich Daniel Ruhmkorff further developed the induction coil, the
Ruhmkorff coil was patented in 1851, and he utilized long windings
of copper wire to achieve a spark of approximately 2 inches
(50 mm) in length. In 1857, after examining a greatly improved
version made by an American inventor, Edward Samuel
Ritchie,[non-primary source needed] Ruhmkorff improved his
design (as did other engineers), using glass insulation and other
innovations to allow the production of sparks more than 300
millimetres (12 in) long.
Middle 19th century
The electromagnetic theory of light adds to the old undulatory theory
an enormous province of transcendent interest and importance; it
demands of us not merely an explanation of all the phenomena of light
and radiant heat by transverse vibrations of an elastic solid called
ether, but also the inclusion of electric currents, of the permanent
magnetism of steel and lodestone, of magnetic force, and of
electrostatic force, in a comprehensive ethereal dynamics."
— Lord Kelvin
Up to the middle of the 19th century, indeed up to about 1870,
electrical science was, it may be said, a sealed book to the majority
of electrical workers. Prior to this time a number of handbooks had
been published on electricity and magnetism, notably Auguste de La
Rive's exhaustive ' Treatise on Electricity,' in 1851 (French) and
1853 (English); August Beer's Einleitung in die Elektrostatik, die
Lehre vom Magnetismus und die Elektrodynamik, Wiedemann's '
Galvanismus,' and Reiss' 'Reibungsal-elektricitat.' But these
works consisted in the main in details of experiments with electricity
and magnetism, and but little with the laws and facts of those
phenomena. Henry d'Abria published the results of some
researches into the laws of induced currents, but owing to their
complexity of the investigation it was not productive of very notable
results. Around the mid-19th century, Fleeming Jenkin's work on '
Electricity and Magnetism ' and Clerk Maxwell's ' Treatise on
Magnetism ' were published.
These books were departures from the beaten path. As Jenkin states in
the preface to his work the science of the schools was so dissimilar
from that of the practical electrician that it was quite impossible to
give students sufficient, or even approximately sufficient, textbooks.
A student he said might have mastered de la Rive's large and valuable
treatise and yet feel as if in an unknown country and listening to an
unknown tongue in the company of practical men. As another writer has
said, with the coming of Jenkin's and Maxwell's books all impediments
in the way of electrical students were removed, "the full meaning of
Ohm's law becomes clear; electromotive force, difference of potential,
resistance, current, capacity, lines of force, magnetization and
chemical affinity were measurable, and could be reasoned about, and
calculations could be made about them with as much certainty as
calculations in dynamics".
About 1850, Kirchhoff published his laws relating to branched or
divided circuits. He also showed mathematically that according to the
then prevailing electrodynamic theory, electricity would be propagated
along a perfectly conducting wire with the velocity of light.
Helmholtz investigated mathematically the effects of induction upon
the strength of a current and deduced therefrom equations, which
experiment confirmed, showing amongst other important points the
retarding effect of self-induction under certain conditions of the
Sir William Thomson.
Sir William Thomson
Sir William Thomson (later Lord Kelvin) predicted as a result
of mathematical calculations the oscillatory nature of the electric
discharge of a condenser circuit. To Henry, however, belongs the
credit of discerning as a result of his experiments in 1842 the
oscillatory nature of the
Leyden jar discharge. He wrote: The
phenomena require us to admit the existence of a principal discharge
in one direction, and then several reflex actions backward and
forward, each more feeble than the preceding, until the equilibrium is
obtained. These oscillations were subsequently observed by B. W.
Feddersen (1857) who using a rotating concave mirror
projected an image of the electric spark upon a sensitive plate,
thereby obtaining a photograph of the spark which plainly indicated
the alternating nature of the discharge.
Sir William Thomson
Sir William Thomson was also
the discoverer of the electric convection of heat (the "Thomson"
effect). He designed for electrical measurements of precision his
quadrant and absolute electrometers. The reflecting galvanometer and
siphon recorder, as applied to submarine cable signaling, are also due
About 1876 the American physicist
Henry Augustus Rowland
Henry Augustus Rowland of Baltimore
demonstrated the important fact that a static charge carried around
produces the same magnetic effects as an electric current.
The Importance of this discovery consists in that it may afford a
plausible theory of magnetism, namely, that magnetism may be the
result of directed motion of rows of molecules carrying static
After Faraday's discovery that electric currents could be developed in
a wire by causing it to cut across the lines of force of a magnet, it
was to be expected that attempts would be made to construct machines
to avail of this fact in the development of voltaic currents. The
first machine of this kind was due to Hippolyte Pixii, 1832. It
consisted of two bobbins of iron wire, opposite which the poles of a
horseshoe magnet were caused to rotate. As this produced in the coils
of the wire an alternating current, Pixii arranged a commutating
device (commutator) that converted the alternating current of the
coils or armature into a direct current in the external circuit. This
machine was followed by improved forms of magneto-electric machines
due to Ritchie, Saxton, Clarke 1834, Stohrer 1843, Nollet 1849,
Shepperd 1856, Van Maldern, Siemens, Wilde and others.
A notable advance in the art of dynamo construction was made by Mr. S.
A. Varley in 1866 and by
Werner von Siemens
Werner von Siemens and Mr. Charles
Wheatstone, who independently discovered that when a coil of
wire, or armature, of the dynamo machine is rotated between the poles
(or in the "field") of an electromagnet, a weak current is set up in
the coil due to residual magnetism in the iron of the electromagnet,
and that if the circuit of the armature be connected with the circuit
of the electromagnet, the weak current developed in the armature
increases the magnetism in the field. This further increases the
magnetic lines of force in which the armature rotates, which still
further increases the current in the electromagnet, thereby producing
a corresponding increase in the field magnetism, and so on, until the
maximum electromotive force which the machine is capable of developing
is reached. By means of this principle the dynamo machine develops its
own magnetic field, thereby much increasing its efficiency and
economical operation. Not by any means, however, was the dynamo
electric machine perfected at the time mentioned.
In 1860 an important improvement had been made by Dr. Antonio
Pacinotti of Pisa who devised the first electric machine with a ring
armature. This machine was first used as an electric motor, but
afterward as a generator of electricity. The discovery of the
principle of the reversibility of the dynamo electric machine
(variously attributed to Walenn 1860;
Pacinotti 1864 ; Fontaine,
Gramme 1873; Deprez 1881, and others) whereby it may be used as an
electric motor or as a generator of electricity has been termed one of
the greatest discoveries of the 19th century.
In 1872 the drum armature was devised by Hefner-Alteneck. This machine
in a modified form was subsequently known as the
Siemens dynamo. These
machines were presently followed by the Schuckert, Gulcher,
Fein,[non-primary source needed] Brush, Hochhausen, Edison
and the dynamo machines of numerous other inventors. In the early days
of dynamo machine construction the machines were mainly arranged as
direct current generators, and perhaps the most important application
of such machines at that time was in electro-plating, for which
purpose machines of low voltage and large current strength were
Beginning about 1887 alternating current generators came into
extensive operation and the commercial development of the transformer,
by means of which currents of low voltage and high current strength
are transformed to currents of high voltage and low current strength,
and vice versa, in time revolutionized the transmission of electric
power to long distances. Likewise the introduction of the rotary
converter (in connection with the "step-down" transformer) which
converts alternating currents into direct currents (and vice versa)
has effected large economies in the operation of electric power
Before the introduction of dynamo electric machines, voltaic, or
primary, batteries were extensively used for electro-plating and in
telegraphy. There are two distinct types of voltaic cells, namely, the
"open" and the "closed", or "constant", type. The open type in brief
is that type which operated on closed circuit becomes, after a short
time, polarized; that is, gases are liberated in the cell which settle
on the negative plate and establish a resistance that reduces the
current strength. After a brief interval of open circuit these gases
are eliminated or absorbed and the cell is again ready for operation.
Closed circuit cells are those in which the gases in the cells are
absorbed as quickly as liberated and hence the output of the cell is
practically uniform. The Leclanché and Daniell cells, respectively,
are familiar examples of the "open" and "closed" type of voltaic cell.
The "open" cells are used very extensively at present, especially in
the dry cell form, and in annunciator and other open circuit signal
systems. Batteries of the Daniell or "gravity" type were employed
almost generally in the United States and Canada as the source of
electromotive force in telegraphy before the dynamo machine became
available, and still are largely used for this service or as "local"
cells. Batteries of the "gravity" and the Edison-Lalande types are
still much used in "closed circuit" systems.
In the late 19th century, the term luminiferous aether, meaning
light-bearing aether, was a conjectured medium for the propagation of
light. The word aether stems via
Latin from the Greek αιθήρ,
from a root meaning to kindle, burn, or shine. It signifies the
substance which was thought in ancient times to fill the upper regions
of space, beyond the clouds.
James Clerk Maxwell.
James Clerk Maxwell
James Clerk Maxwell of Edinburgh announced his electromagnetic
theory of light, which was perhaps the greatest single step in the
world's knowledge of electricity. Maxwell had studied and
commented on the field of electricity and magnetism as early as 1855/6
when On Faraday's lines of force was read to the Cambridge
Philosophical Society. The paper presented a simplified model of
Faraday's work, and how the two phenomena were related. He reduced all
of the current knowledge into a linked set of differential equations
with 20 equations in 20 variables. This work was later published as On
Physical Lines of Force in March 1861. In order to determine the
force which is acting on any part of the machine we must find its
momentum, and then calculate the rate at which this momentum is being
changed. This rate of change will give us the force. The method of
calculation which it is necessary to employ was first given by
Lagrange, and afterwards developed, with some modifications, by
Hamilton's equations. It is usually referred to as Hamilton's
principle; when the equations in the original form are used they are
known as Lagrange's equations. Now Maxwell logically showed how these
methods of calculation could be applied to the electro-magnetic
field. The energy of a dynamical system is partly kinetic, partly
potential. Maxwell supposes that the magnetic energy of the field is
kinetic energy, the electric energy potential.
Around 1862, while lecturing at King's College, Maxwell calculated
that the speed of propagation of an electromagnetic field is
approximately that of the speed of light. He considered this to be
more than just a coincidence, and commented "We can scarcely avoid the
conclusion that light consists in the transverse undulations of the
same medium which is the cause of electric and magnetic
Working on the problem further, Maxwell showed that the equations
predict the existence of waves of oscillating electric and magnetic
fields that travel through empty space at a speed that could be
predicted from simple electrical experiments; using the data available
at the time, Maxwell obtained a velocity of 310,740,000 m/s. In his
1864 paper A Dynamical Theory of the Electromagnetic Field, Maxwell
wrote, The agreement of the results seems to show that light and
magnetism are affections of the same substance, and that light is an
electromagnetic disturbance propagated through the field according to
As already noted herein Faraday, and before him, Ampère and others,
had inklings that the luminiferous ether of space was also the medium
for electric action. It was known by calculation and experiment that
the velocity of electricity was approximately 186,000 miles per
second; that is, equal to the velocity of light, which in itself
suggests the idea of a relationship between -electricity and "light."
A number of the earlier philosophers or mathematicians, as Maxwell
terms them, of the 19th century, held the view that electromagnetic
phenomena were explainable by action at a distance. Maxwell, following
Faraday, contended that the seat of the phenomena was in the medium.
The methods of the mathematicians in arriving at their results were
synthetical while Faraday's methods were analytical. Faraday in his
mind's eye saw lines of force traversing all space where the
mathematicians saw centres of force attracting at a distance. Faraday
sought the seat of the phenomena in real actions going on in the
medium; they were satisfied that they had found it in a power of
action at a distance on the electric fluids.
Both of these methods, as Maxwell points out, had succeeded in
explaining the propagation of light as an electromagnetic phenomenon
while at the same time the fundamental conceptions of what the
quantities concerned are, radically differed. The mathematicians
assumed that insulators were barriers to electric currents; that, for
instance, in a
Leyden jar or electric condenser the electricity was
accumulated at one plate and that by some occult action at a distance
electricity of an opposite kind was attracted to the other plate.
Maxwell, looking further than Faraday, reasoned that if light is an
electromagnetic phenomenon and is transmissible through dielectrics
such as glass, the phenomenon must be in the nature of electromagnetic
currents in the dielectrics. He therefore contended that in the
charging of a condenser, for instance, the action did not stop at the
insulator, but that some "displacement" currents are set up in the
insulating medium, which currents continue until the resisting force
of the medium equals that of the charging force. In a closed conductor
circuit, an electric current is also a displacement of electricity.
The conductor offers a certain resistance, akin to friction, to the
displacement of electricity, and heat is developed in the conductor,
proportional to the square of the current(as already stated herein),
which current flows as long as the impelling electric force continues.
This resistance may be likened to that met with by a ship as it
displaces in the water in its progress. The resistance of the
dielectric is of a different nature and has been compared to the
compression of multitudes of springs, which, under compression, yield
with an increasing back pressure, up to a point where the total back
pressure equals the initial pressure. When the initial pressure is
withdrawn the energy expended in compressing the "springs" is returned
to the circuit, concurrently with the return of the springs to their
original condition, this producing a reaction in the opposite
direction. Consequently, the current due to the displacement of
electricity in a conductor may be continuous, while the displacement
currents in a dielectric are momentary and, in a circuit or medium
which contains but little resistance compared with capacity or
inductance reaction, the currents of discharge are of an oscillatory
or alternating nature.
Maxwell extended this view of displacement currents in dielectrics to
the ether of free space. Assuming light to be the manifestation of
alterations of electric currents in the ether, and vibrating at the
rate of light vibrations, these vibrations by induction set up
corresponding vibrations in adjoining portions of the ether, and in
this way the undulations corresponding to those of light are
propagated as an electromagnetic effect in the ether. Maxwell's
electromagnetic theory of light obviously involved the existence of
electric waves in free space, and his followers set themselves the
task of experimentally demonstrating the truth of the theory. By 1871,
he presented the Remarks on the mathematical classification of
End of the 19th century
In 1887, the German physicist
Heinrich Hertz in a series of
experiments proved the actual existence of electromagnetic waves,
showing that transverse free space electromagnetic waves can travel
over some distance as predicted by Maxwell and Faraday. Hertz
published his work in a book titled: Electric waves: being researches
on the propagation of electric action with finite velocity through
space. The discovery of electromagnetic waves in space led to the
development of radio in the closing years of the 19th century.
The electron as a unit of charge in electrochemistry was posited by G.
Johnstone Stoney in 1874, who also coined the term electron in
1894. Plasma was first identified in a Crookes tube, and so
Sir William Crookes
Sir William Crookes in 1879 (he called it "radiant
matter"). The place of electricity in leading up to the discovery
of those beautiful phenomena of the Crookes Tube (due to Sir William
Cathode rays, and later to the discovery of
Roentgen or X-rays, must not be overlooked, since without electricity
as the excitant of the tube the discovery of the rays might have been
postponed indefinitely. It has been noted herein that Dr. William
Gilbert was termed the founder of electrical science. This must,
however, be regarded as a comparative statement.
Oliver Heaviside was a self-taught scholar who reformulated Maxwell's
field equations in terms of electric and magnetic forces and energy
flux, and independently co-formulated vector analysis. His series of
articles continued the work entitled "Electromagnetic Induction and
its Propagation", commenced in
The Electrician in 1885 to nearly 1887
(ed., the latter part of the work dealing with the propagation of
electromagnetic waves along wires through the dielectric surrounding
them), when the great pressure on space and the want of readers
appeared to necessitate its abrupt discontinuance. (A straggler
piece appeared December 31, 1887.) He wrote an interpretation of the
transcendental formulae of electromagnetism. Following the real object
of true naturalists when they employ mathematics to assist them,
he wrote to find out the connections of known phenomena, and by
deductive reasoning, to obtain a knowledge of electromagnetic
phenomena. Although at odds with the scientific establishment for most
of his life, Heaviside changed the face of mathematics and science for
years to come.
Of the changes in the field of electromagnetic theory, certain
conclusions from Electro-
Magnetic Theory[non-primary source
needed] by Heaviside are, if not drawn, at least indicated in this
book. Two of them may be stated as follows:
That magnetism is a phenomenon of motion and not a statical
phenomenon; also that this motion is more likely to be translational
That all electric currents are phenomena consequent upon the emission
of electro-magnetic wave disturbances in the aether, and that the
proper treatment of all the phenomena of currents and magnetic flux
should be considered as the consequence, and not as the cause, of
The ultimate results of his work are twofold. (1) The first ultimate
result is purely mathematical, which is important only to those who
study mathematical physics. The system of vectorial algebra as
developed by Mr. Heaviside was used because of ease for physical
investigations to the methods of quaternions. (2) The second ultimate
result is physical. It consists in more closely uniting the more
recondite problems of telegraphy, telephony, Teslaic phenomena and
Hertzian phenomena with the fundamental properties of the aether. In
elucidating this connection, the merit of the book appears most
prominently as a stepping-stone to the goal in the full view of all
physical analysis, namely, the resolution of all physical phenomena to
the activities of the aether, and of matter in the aether, under the
laws of dynamics.[non-primary source needed]
During the late 1890s a number of physicists proposed that
electricity, as observed in studies of electrical conduction in
conductors, electrolytes, and cathode ray tubes, consisted of discrete
units, which were given a variety of names, but the reality of these
units had not been confirmed in a compelling way. However, there were
also indications that the cathode rays had wavelike properties.
Faraday, Weber, Helmholtz, Clifford and others had glimpses of this
view; and the experimental works of Zeeman, Goldstein, Crookes, J. J.
Thomson and others had greatly strengthened this view. Weber predicted
that electrical phenomena were due to the existence of electrical
atoms, the influence of which on one another depended on their
position and relative accelerations and velocities.
others also contended that the existence of electrical atoms followed
from Faraday's laws of electrolysis, and Johnstone Stoney, to whom is
due the term "electron", showed that each chemical ion of the
decomposed electrolyte carries a definite and constant quantity of
electricity, and inasmuch as these charged ions are separated on the
electrodes as neutral substances there must be an instant, however
brief, when the charges must be capable of existing separately as
electrical atoms; while in 1887, Clifford wrote: "There is great
reason to believe that every material atom carries upon it a small
electric current, if it does not wholly consist of this current."
J. J. Thomson
J. J. Thomson
J. J. Thomson performed experiments indicating that cathode
rays really were particles, found an accurate value for their
charge-to-mass ratio e/m, and found that e/m was independent of
cathode material. He made good estimates of both the charge e and the
mass m, finding that cathode ray particles, which he called
"corpuscles", had perhaps one thousandth of the mass of the least
massive ion known (hydrogen). He further showed that the negatively
charged particles produced by radioactive materials, by heated
materials, and by illuminated materials, were universal. The nature of
Crookes tube "cathode ray" matter was identified by Thomson in
1897.[non-primary source needed]
In the late 19th century, the
Michelson–Morley experiment was
Albert A. Michelson
Albert A. Michelson and
Edward W. Morley at what is now
Case Western Reserve University. It is generally considered to be the
evidence against the theory of a luminiferous aether. The experiment
has also been referred to as "the kicking-off point for the
theoretical aspects of the Second Scientific Revolution."
Primarily for this work, Michelson was awarded the
Nobel Prize in
Dayton Miller continued with experiments, conducting thousands
of measurements and eventually developing the most accurate
interferometer in the world at that time. Miller and others, such as
Morley, continue observations and experiments dealing with the
concepts. A range of proposed aether-dragging theories could
explain the null result but these were more complex, and tended to use
arbitrary-looking coefficients and physical assumptions.
By the end of the 19th century electrical engineers had become a
distinct profession, separate from physicists and inventors. They
created companies that investigated, developed and perfected the
techniques of electricity transmission, and gained support from
governments all over the world for starting the first worldwide
electrical telecommunication network, the telegraph network. Pioneers
in this field included Werner von Siemens, founder of
Siemens AG in
1847, and John Pender, founder of Cable & Wireless.
The first public demonstration of a "alternator system" took place in
1886. Large two-phase alternating current generators
were built by a British electrician, J. E. H. Gordon,[non-primary
source needed] in 1882.
Lord Kelvin and Sebastian Ferranti also
developed early alternators, producing frequencies between 100 and 300
hertz. After 1891, polyphase alternators were introduced to supply
currents of multiple differing phases. Later alternators were
designed for varying alternating-current frequencies between sixteen
and about one hundred hertz, for use with arc lighting, incandescent
lighting and electric motors.
The possibility of obtaining the electric current in large quantities,
and economically, by means of dynamo electric machines gave impetus to
the development of incandescent and arc lighting. Until these machines
had attained a commercial basis voltaic batteries were the only
available source of current for electric lighting and power. The cost
of these batteries, however, and the difficulties of maintaining them
in reliable operation were prohibitory of their use for practical
lighting purposes. The date of the employment of arc and incandescent
lamps may be set at about 1877.
Even in 1880, however, but little headway had been made toward the
general use of these illuminants; the rapid subsequent growth of this
industry is a matter of general knowledge. The employment of
storage batteries, which were originally termed secondary batteries or
accumulators, began about 1879. Such batteries are now utilized on a
large scale as auxiliaries to the dynamo machine in electric
power-houses and substations, in electric automobiles and in immense
numbers in automobile ignition and starting systems, also in fire
alarm telegraphy and other signal systems.
World's Fair Tesla presentation.
In 1893, the World's Columbian International Exposition was held in a
building which was devoted to electrical exhibits. General Electric
Company (backed by Edison and J. P. Morgan) had proposed to power the
electric exhibits with direct current at the cost of one million
dollars. However, Westinghouse proposed to illuminate the Columbian
Exposition in Chicago with alternating current for half that price,
and Westinghouse won the bid. It was an historical moment and the
beginning of a revolution, as
George Westinghouse introduced the
public to electrical power by illuminating the Exposition.
Second Industrial Revolution
Main article: Second Industrial Revolution
Between 1885 and 1890
Galileo Ferraris in Italy,
Nikola Tesla in the
United States, and
Mikhail Dolivo-Dobrovolsky in Germany explored
poly-phase currents combined with electromagnetic induction leading to
the development of practical AC induction motors. The AC
induction motor helped usher in the Second Industrial Revolution. The
rapid advance of electrical technology in the latter 19th and early
20th centuries led to commercial rivalries. In the
War of Currents
War of Currents in
the late 1880s,
George Westinghouse and
Thomas Edison became
adversaries due to Edison's promotion of direct current (DC) for
electric power distribution over alternating current (AC) advocated by
Several inventors helped develop commercial systems. Samuel Morse,
inventor of a long-range telegraph; Thomas Edison, inventor of the
first commercial electrical energy distribution network; George
Westinghouse, inventor of the electric locomotive; Alexander Graham
Bell, the inventor of the telephone and founder of a successful
In 1871 the electric telegraph had grown to large proportions and was
in use in every civilized country in the world, its lines forming a
network in all directions over the surface of the land. The system
most generally in use was the electromagnetic telegraph due to S. F.
B. Morse of New York, or modifications of his system. Submarine
cables connecting the Eastern and Western hemispheres were also
in successful operation at that time.
When, however, in 1918 one views the vast applications of electricity
to electric light, electric railways, electric power and other
purposes (all it may be repeated made possible and practicable by the
perfection of the dynamo machine), it is difficult to believe that no
longer ago than 1871 the author of a book published in that year, in
referring to the state of the art of applied electricity at that time,
could have truthfully written: "The most important and remarkable of
the uses which have been made of electricity consists in its
application to telegraph purposes". The statement was, however,
quite accurate and perhaps the time could have been carried forward to
the year 1876 without material modification of the remarks. In that
year the telephone, due to Alexander Graham Bell, was invented, but it
was not until several years thereafter that its commercial employment
began in earnest. Since that time also the sister branches of
electricity just mentioned have advanced and are advancing with such
gigantic strides in every direction that it is difficult to place a
limit upon their progress. Electrical devices account of the use of
electricity in the arts and industries.
Charles Proteus Steinmetz, theoretician of alternating current.
The 1880s saw the spread of large scale commercial electric power
systems, first used for lighting and eventually for electro-motive
power and heating. Systems early on used alternating current and
direct current. Large centralized power generation became possible
when it was recognized that alternating current electric power lines
could use transformers to take advantage of the fact that each
doubling of the voltage would allow the same size cable to transmit
the same amount of power four times the distance.
used to raise voltage at the point of generation (a representative
number is a generator voltage in the low kilovolt range) to a much
higher voltage (tens of thousands to several hundred thousand volts)
for primary transmission, followed to several downward
transformations, for commercial and residential domestic use.
The International Electro-Technical Exhibition of 1891 featuring the
long distance transmission of high-power, three-phase electric
current. It was held between 16 May and 19 October on the disused site
of the three former "Westbahnhöfe" (Western Railway Stations) in
Frankfurt am Main. The exhibition featured the first long distance
transmission of high-power, three-phase electric current, which was
generated 175 km away at Lauffen am Neckar. As a result of this
successful field trial, three-phase current became established for
electrical transmission networks throughout the world.
Much was done in the direction in the improvement of railroad terminal
facilities, and it is difficult to find one steam railroad engineer
who would have denied that all the important steam railroads of this
country were not to be operated electrically. In other directions the
progress of events as to the utilization of electric power was
expected to be equally rapid. In every part of the world the power of
falling water, nature's perpetual motion machine, which has been going
to waste since the world began, is now being converted into
electricity and transmitted by wire hundreds of miles to points where
it is usefully and economically employed.
The first windmill for electricity production was built in
July 1887 by the Scottish electrical engineer James Blyth. Across
the Atlantic, in
Cleveland, Ohio a larger and heavily engineered
machine was designed and constructed in 1887–88 by Charles F.
Brush,[non-primary source needed] this was built by his
engineering company at his home and operated from 1886 until
1900. The Brush wind turbine had a rotor 56 feet (17 m) in
diameter and was mounted on a 60-foot (18 m) tower. Although large by
today's standards, the machine was only rated at 12 kW; it turned
relatively slowly since it had 144 blades. The connected dynamo was
used either to charge a bank of batteries or to operate up to 100
incandescent light bulbs, three arc lamps, and various motors in
Brush's laboratory. The machine fell into disuse after 1900 when
electricity became available from Cleveland's central stations, and
was abandoned in 1908.
Various units of electricity and magnetism have been adopted and named
by representatives of the electrical engineering institutes of the
world, which units and names have been confirmed and legalized by the
governments of the United States and other countries. Thus the volt,
from the Italian Volta, has been adopted as the practical unit of
electromotive force, the ohm, from the enunciator of Ohm's law, as the
practical unit of resistance; the ampere, after the eminent French
scientist of that name, as the practical unit of current strength, the
henry as the practical unit of inductance, after
Joseph Henry and in
recognition of his early and important experimental work in mutual
John Ambrose Fleming
John Ambrose Fleming predicted that at absolute zero, pure
metals would become perfect electromagnetic conductors (though, later,
Dewar altered his opinion on the disappearance of resistance believing
that there would always be some resistance). Walther Hermann Nernst
developed the third law of thermodynamics and stated that absolute
zero was unattainable.
Carl von Linde
Carl von Linde and William Hampson, both
commercial researchers, nearly at the same time filed for patents on
the Joule–Thomson effect. Linde's patent was the climax of 20 years
of systematic investigation of established facts, using a regenerative
counterflow method. Hampson's design was also of a regenerative
method. The combined process became known as the Linde–Hampson
Heike Kamerlingh Onnes
Heike Kamerlingh Onnes purchased a Linde machine
for his research.
Zygmunt Florenty Wróblewski
Zygmunt Florenty Wróblewski conducted research into
electrical properties at low temperatures, though his research ended
early due to his accidental death. Around 1864,
Karol Olszewski and
Wroblewski predicted the electrical phenomena of dropping resistance
levels at ultra-cold temperatures. Olszewski and Wroblewski documented
evidence of this in the 1880s. A milestone was achieved on 10 July
1908 when Onnes at the
Leiden University in
Leiden produced, for the
first time, liquified helium and achieved superconductivity.
William Du Bois Duddell
William Du Bois Duddell develops the
Singing Arc and produced
melodic sounds, from a low to a high-tone, from this arc lamp.
Lorentz and Poincaré
History of special relativity
History of special relativity and Lorentz ether theory
Between 1900 and 1910, many scientists like Wilhelm Wien, Max Abraham,
Hermann Minkowski, or
Gustav Mie believed that all forces of nature
are of electromagnetic origin (the so-called "electromagnetic world
view"). This was connected with the electron theory developed between
1892 and 1904 by Hendrik Lorentz. Lorentz introduced a strict
separation between matter (electrons) and the aether, whereby in his
model the ether is completely motionless, and it won't be set in
motion in the neighborhood of ponderable matter. Contrary to other
electron models before, the electromagnetic field of the ether appears
as a mediator between the electrons, and changes in this field can
propagate not faster than the speed of light.
In 1896, three years after submitting his thesis on the Kerr effect,
Pieter Zeeman disobeyed the direct orders of his supervisor and used
laboratory equipment to measure the splitting of spectral lines by a
strong magnetic field. Lorentz theoretically explained the Zeeman
effect on the basis of his theory, for which both received the Nobel
Prize in Physics in 1902. A fundamental concept of Lorentz's theory in
1895 was the "theorem of corresponding states" for terms of order v/c.
This theorem states that a moving observer (relative to the ether)
makes the same observations as a resting observer. This theorem was
extended for terms of all orders by Lorentz in 1904. Lorentz noticed,
that it was necessary to change the space-time variables when changing
frames and introduced concepts like physical length contraction (1892)
to explain the Michelson–Morley experiment, and the mathematical
concept of local time (1895) to explain the aberration of light and
the Fizeau experiment. That resulted in the formulation of the
Lorentz transformation by
Joseph Larmor (1897, 1900) and
Lorentz (1899, 1904). As Lorentz later noted (1921,
1928), he considered the time indicated by clocks resting in the
aether as "true" time, while local time was seen by him as a heuristic
working hypothesis and a mathematical artifice. Therefore,
Lorentz's theorem is seen by modern historians as being a mathematical
transformation from a "real" system resting in the aether into a
"fictitious" system in motion.
Continuing the work of Lorentz,
Henri Poincaré between 1895 and 1905
formulated on many occasions the principle of relativity and tried to
harmonize it with electrodynamics. He declared simultaneity only a
convenient convention which depends on the speed of light, whereby the
constancy of the speed of light would be a useful postulate for making
the laws of nature as simple as possible. In 1900 he interpreted
Lorentz's local time as the result of clock synchronization by light
signals, and introduced the electromagnetic momentum by comparing
electromagnetic energy to what he called a "fictitious fluid" of mass
displaystyle m=E/c^ 2
. And finally in June and July 1905 he declared the relativity
principle a general law of nature, including gravitation. He corrected
some mistakes of Lorentz and proved the
Lorentz covariance of the
electromagnetic equations. Poincaré also suggested that there exist
non-electrical forces to stabilize the electron configuration and
asserted that gravitation is a non-electrical force as well, contrary
to the electromagnetic world view. However, historians pointed out
that he still used the notion of an ether and distinguished between
"apparent" and "real" time and therefore didn't invent special
relativity in its modern understanding.
Einstein's Annus Mirabilis
Main article: Annus Mirabilis papers
Albert Einstein, 1905
In 1905, while he was working in the patent office, Albert Einstein
had four papers published in the Annalen der Physik, the leading
German physics journal. These are the papers that history has come to
call the Annus Mirabilis papers:
His paper on the particulate nature of light put forward the idea that
certain experimental results, notably the photoelectric effect, could
be simply understood from the postulate that light interacts with
matter as discrete "packets" (quanta) of energy, an idea that had been
Max Planck in 1900 as a purely mathematical
manipulation, and which seemed to contradict contemporary wave
theories of light (Einstein 1905a). This was the only work of
Einstein's that he himself called "revolutionary."
His paper on
Brownian motion explained the random movement of very
small objects as direct evidence of molecular action, thus supporting
the atomic theory. (Einstein 1905b)
His paper on the electrodynamics of moving bodies introduced the
radical theory of special relativity, which showed that the observed
independence of the speed of light on the observer's state of motion
required fundamental changes to the notion of simultaneity.
Consequences of this include the time-space frame of a moving body
slowing down and contracting (in the direction of motion) relative to
the frame of the observer. This paper also argued that the idea of a
luminiferous aether—one of the leading theoretical entities in
physics at the time—was superfluous. (Einstein 1905c)
In his paper on mass–energy equivalence (previously considered to be
distinct concepts), Einstein deduced from his equations of special
relativity what later became the well-known expression:
displaystyle E=mc^ 2
, suggesting that tiny amounts of mass could be converted into huge
amounts of energy. (Einstein 1905d)
All four papers are today recognized as tremendous achievements—and
hence 1905 is known as Einstein's "Wonderful Year". At the time,
however, they were not noticed by most physicists as being important,
and many of those who did notice them rejected them outright. Some of
this work—such as the theory of light quanta—remained
controversial for years.
The first formulation of a quantum theory describing radiation and
matter interaction is due to Paul Dirac, who, during 1920, was first
able to compute the coefficient of spontaneous emission of an
Paul Dirac described the quantization of the
electromagnetic field as an ensemble of harmonic oscillators with the
introduction of the concept of creation and annihilation operators of
particles. In the following years, with contributions from Wolfgang
Pauli, Eugene Wigner, Pascual Jordan,
Werner Heisenberg and an elegant
formulation of quantum electrodynamics due to Enrico Fermi,
physicists came to believe that, in principle, it would be possible to
perform any computation for any physical process involving photons and
charged particles. However, further studies by
Felix Bloch with Arnold
Nordsieck, and Victor Weisskopf, in 1937 and 1939, revealed
that such computations were reliable only at a first order of
perturbation theory, a problem already pointed out by Robert
Oppenheimer. At higher orders in the series infinities emerged,
making such computations meaningless and casting serious doubts on the
internal consistency of the theory itself. With no solution for this
problem known at the time, it appeared that a fundamental
incompatibility existed between special relativity and quantum
In December 1938, the German chemists
Otto Hahn and Fritz Strassmann
sent a manuscript to
Naturwissenschaften reporting they had detected
the element barium after bombarding uranium with neutrons;
simultaneously, they communicated these results to Lise Meitner.
Meitner, and her nephew Otto Robert Frisch, correctly interpreted
these results as being nuclear fission. Frisch confirmed this
experimentally on 13 January 1939. In 1944, Hahn received
Nobel Prize in Chemistry for the discovery of nuclear fission.
Some historians who have documented the history of the discovery of
nuclear fission believe Meitner should have been awarded the Nobel
Prize with Hahn.
Difficulties with the
Quantum theory increased through the end of
1940. Improvements in microwave technology made it possible to take
more precise measurements of the shift of the levels of a hydrogen
atom, now known as the
Lamb shift and magnetic moment of the
electron. These experiments unequivocally exposed discrepancies
which the theory was unable to explain. With the invention of bubble
chambers and spark chambers in the 1950s, experimental particle
physics discovered a large and ever-growing number of particles called
hadrons. It seemed that such a large number of particles could not all
Shortly after the end of the war in 1945, Bell Labs formed a Solid
State Physics Group, led by
William Shockley and chemist Stanley
Morgan; other personnel including
John Bardeen and Walter Brattain,
physicist Gerald Pearson, chemist Robert Gibney, electronics expert
Hilbert Moore and several technicians. Their assignment was to seek a
solid-state alternative to fragile glass vacuum tube amplifiers. Their
first attempts were based on Shockley's ideas about using an external
electrical field on a semiconductor to affect its conductivity. These
experiments failed every time in all sorts of configurations and
materials. The group was at a standstill until Bardeen suggested a
theory that invoked surface states that prevented the field from
penetrating the semiconductor. The group changed its focus to study
these surface states and they met almost daily to discuss the work.
The rapport of the group was excellent, and ideas were freely
As to the problems in the electron experiments, a path to a solution
was given by Hans Bethe. In 1947, while he was traveling by train to
reach Schenectady from New York, after giving a talk at the
conference at Shelter Island on the subject, Bethe completed the first
non-relativistic computation of the shift of the lines of the hydrogen
atom as measured by Lamb and Retherford. Despite the limitations
of the computation, agreement was excellent. The idea was simply to
attach infinities to corrections at mass and charge that were actually
fixed to a finite value by experiments. In this way, the infinities
get absorbed in those constants and yield a finite result in good
agreement with experiments. This procedure was named renormalization.
Based on Bethe's intuition and fundamental papers on the subject by
Shin'ichirō Tomonaga, Julian Schwinger, Richard
Feynman and Freeman Dyson, it was finally
possible to get fully covariant formulations that were finite at any
order in a perturbation series of quantum electrodynamics.
Julian Schwinger and
Richard Feynman were
jointly awarded with a
Nobel Prize in Physics in 1965 for their work
in this area. Their contributions, and those of Freeman Dyson,
were about covariant and gauge-invariant formulations of quantum
electrodynamics that allow computations of observables at any order of
perturbation theory. Feynman's mathematical technique, based on his
diagrams, initially seemed very different from the field-theoretic,
operator-based approach of Schwinger and Tomonaga, but Freeman Dyson
later showed that the two approaches were equivalent.
Renormalization, the need to attach a physical meaning at certain
divergences appearing in the theory through integrals, has
subsequently become one of the fundamental aspects of quantum field
theory and has come to be seen as a criterion for a theory's general
acceptability. Even though renormalization works very well in
practice, Feynman was never entirely comfortable with its mathematical
validity, even referring to renormalization as a "shell game" and
"hocus pocus". QED has served as the model and template for all
subsequent quantum field theories. Peter Higgs, Jeffrey Goldstone, and
others, Sheldon Glashow,
Steven Weinberg and
Abdus Salam independently
showed how the weak nuclear force and quantum electrodynamics could be
merged into a single electroweak force.
Robert Noyce credited
Kurt Lehovec for the principle of p–n junction
isolation caused by the action of a biased p-n junction (the diode) as
a key concept behind the integrated circuit.
Jack Kilby recorded
his initial ideas concerning the integrated circuit in July 1958 and
successfully demonstrated the first working integrated circuit on
September 12, 1958. In his patent application of February 6,
1959, Kilby described his new device as "a body of semiconductor
material ... wherein all the components of the electronic circuit are
completely integrated." Kilby won the 2000
Nobel Prize in Physics
for his part of the invention of the integrated circuit. Robert
Noyce also came up with his own idea of an integrated circuit half a
year later than Kilby. Noyce's chip solved many practical problems
that Kilby's had not. Noyce's chip, made at Fairchild Semiconductor,
was made of silicon, whereas Kilby's chip was made of germanium.
Philo Farnsworth developed the Farnsworth–Hirsch Fusor, or simply
fusor, an apparatus designed by Farnsworth to create nuclear fusion.
Unlike most controlled fusion systems, which slowly heat a
magnetically confined plasma, the fusor injects high temperature ions
directly into a reaction chamber, thereby avoiding a considerable
amount of complexity. When the Farnsworth-Hirsch
Fusor was first
introduced to the fusion research world in the late 1960s, the Fusor
was the first device that could clearly demonstrate it was producing
fusion reactions at all. Hopes at the time were high that it could be
quickly developed into a practical power source. However, as with
other fusion experiments, development into a power source has proven
difficult. Nevertheless, the fusor has since become a practical
neutron source and is produced commercially for this role.
The mirror image of an electromagnet produces a field with the
opposite polarity. Thus the north and south poles of a magnet have the
same symmetry as left and right. Prior to 1956, it was believed that
this symmetry was perfect, and that a technician would be unable to
distinguish the north and south poles of a magnet except by reference
to left and right. In that year, T. D. Lee and C. N. Yang predicted
the nonconservation of parity in the weak interaction. To the surprise
of many physicists, in 1957 C. S. Wu and collaborators at the U.S.
National Bureau of Standards demonstrated that under suitable
conditions for polarization of nuclei, the beta decay of cobalt-60
preferentially releases electrons toward the south pole of an external
magnetic field, and a somewhat higher number of gamma rays toward the
north pole. As a result, the experimental apparatus does not behave
comparably with its mirror image.
The first step towards the
Standard Model was Sheldon Glashow's
discovery, in 1960, of a way to combine the electromagnetic and weak
interactions. In 1967, Steven Weinberg and Abdus Salam
incorporated the Higgs mechanism into Glashow's
electroweak theory, giving it its modern form. The
Higgs mechanism is
believed to give rise to the masses of all the elementary particles in
the Standard Model. This includes the masses of the W and Z bosons,
and the masses of the fermions - i.e. the quarks and leptons. After
the neutral weak currents caused by Z boson exchange were discovered
CERN in 1973, the electroweak theory became
widely accepted and Glashow, Salam, and Weinberg shared the 1979 Nobel
Prize in Physics for discovering it. The
W and Z bosons
W and Z bosons were
discovered experimentally in 1981, and their masses were found to be
Standard Model predicted. The theory of the strong interaction,
to which many contributed, acquired its modern form around 1973–74,
when experiments confirmed that the hadrons were composed of
fractionally charged quarks. With the establishment of quantum
chromodynamics in the 1970s finalized a set of fundamental and
exchange particles, which allowed for the establishment of a "standard
model" based on the mathematics of gauge invariance, which
successfully described all forces except for gravity, and which
remains generally accepted within the domain to which it is designed
to be applied.
The 'standard model' groups the electroweak interaction theory and
quantum chromodynamics into a structure denoted by the gauge group
SU(3)×SU(2)×U(1). The formulation of the unification of the
electromagnetic and weak interactions in the standard model is due to
Steven Weinberg and, subsequently, Sheldon Glashow. After
the discovery, made at CERN, of the existence of neutral weak
currents, mediated by the Z boson foreseen in the
standard model, the physicists Salam, Glashow and Weinberg received
Nobel Prize in Physics for their electroweak theory.
Since then, discoveries of the bottom quark (1977), the top quark
(1995) and the tau neutrino (2000) have given credence to the standard
model. Because of its success in explaining a wide variety of
Main article: Electrodynamic tether
Before the start of the 21st century, the electrodynamic tether
being oriented at an angle to the local vertical between the object
and a planet with a magnetic field cut the Earth's magnetic field and
generated a current; thereby it converted some of the orbiting body's
kinetic energy to electrical energy. The tether's far end can be left
bare, making electrical contact with the ionosphere, creating a
generator. As part of a tether propulsion system, crafts can use long,
strong conductors to change the orbits of spacecraft. It has the
potential to make space travel significantly cheaper. It is a
simplified, very low-budget magnetic sail. It can be used either to
accelerate or brake an orbiting spacecraft. When direct current is
pumped through the tether, it exerts a force against the magnetic
field, and the tether accelerates the spacecraft.
There are a range of emerging energy technologies. By 2007, solid
state micrometer-scale electric double-layer capacitors based on
advanced superionic conductors had been for low-voltage electronics
such as deep-sub-voltage nanoelectronics and related technologies (the
22 nm technological node of CMOS and beyond). Also, the nanowire
battery, a lithium-ion battery, was invented by a team led by Dr. Yi
Cui in 2007.
Reflecting the fundamental importance and applicability of Magnetic
resonance imaging in medicine,
Paul Lauterbur of the University
of Illinois at Urbana-Champaign and Sir
Peter Mansfield of the
University of Nottingham
University of Nottingham were awarded the 2003
Nobel Prize in
Physiology or Medicine for their "discoveries concerning magnetic
resonance imaging". The Nobel citation acknowledged Lauterbur's
insight of using magnetic field gradients to determine spatial
localization, a discovery that allowed rapid acquisition of 2D images.
Main article: wireless energy transfer
Wireless electricity is a form of wireless energy transfer, the
ability to provide electrical energy to remote objects without wires.
WiTricity was coined in 2005 by Dave Gerding and later used
for a project led by Prof.
Marin Soljačić in 2007. The MIT
researchers successfully demonstrated the ability to power a 60 watt
light bulb wirelessly, using two 5-turn copper coils of 60 cm
(24 in) diameter, that were 2 m (7 ft) away, at roughly
45% efficiency. This technology can potentially be used in a
large variety of applications, including consumer, industrial, medical
and military. Its aim is to reduce the dependence on batteries.
Further applications for this technology include transmission of
information—it would not interfere with radio waves and thus could
be used as a cheap and efficient communication device without
requiring a license or a government permit.
Further information: WiTricity
Main article: Grand Unified Theory
As of 2017[update], there is still no hard evidence that nature is
described by a
Grand Unified Theory
Grand Unified Theory (GUT). The
Higgs particle has been
tentatively verified,. The discovery of neutrino oscillations
indicates that the
Standard Model is incomplete and has led to renewed
interest toward certain GUT such as
. One of the few possible experimental tests of certain GUT is proton
decay and also fermion masses. There are a few more special tests for
supersymmetric GUT. The gauge coupling strengths of QCD, the weak
interaction and hypercharge seem to meet at a common length scale
called the GUT scale and equal approximately to
displaystyle 10^ 16
GeV, which is slightly suggestive. This interesting numerical
observation is called the gauge coupling unification, and it works
particularly well if one assumes the existence of superpartners of the
Standard Model particles. Still it is possible to achieve the same by
postulating, for instance, that ordinary (non supersymmetric)
models break with an intermediate gauge scale, such as the one of
Theory of Everything
Theory of Everything (TOE) is a putative theory of theoretical
physics that fully explains and links together all known physical
phenomena, and, ideally, has predictive power for the outcome of any
experiment that could be carried out in principle.
M-Theory is not yet
complete, but the underlying structure of the mathematics has been
established and is in agreement with not only all the string theories,
but with all of our scientific observations of the universe.
Furthermore, it has passed many tests of internal mathematical
consistency that many other attempts to combine quantum mechanics and
gravity had failed. Unfortunately, until we can find some way to
observe higher dimensions (impossible with our current level of
M-Theory has a very difficult time making predictions
which can be tested in a laboratory. Technologically, it may never be
possible for it to be "proven".
Physicist and author
Michio Kaku has
M-Theory may present us with a "Theory of Everything"
which is so concise that its underlying formula would fit on a
Stephen Hawking originally believed that
M-Theory may be
the ultimate theory but later suggested that the search for
understanding of mathematics and physics will never be complete.
See also: Unified field theory
Main article: Open problems in physics
The magnetic monopole in the quantum theory of magnetic charge
started with a paper by the physicist
Paul A.M. Dirac
Paul A.M. Dirac in 1931.
The detection of magnetic monopoles is an open problem in experimental
physics. In some theoretical models, magnetic monopoles are unlikely
to be observed, because they are too massive to be created in particle
accelerators, and also too rare in the Universe to enter a particle
detector with much probability.
After more than twenty years of intensive research, the origin of
high-temperature superconductivity is still not clear, but it seems
that instead of electron-phonon attraction mechanisms, as in
conventional superconductivity, one is dealing with genuine electronic
mechanisms (e.g. by antiferromagnetic correlations), and instead of
s-wave pairing, d-wave pairings are substantial. One goal of
all this research is room-temperature superconductivity.
History of electromagnetic spectrum, History of electrical
engineering, History of Maxwell's equations, History of radio, History
of optics, History of physics
Biot–Savart law, Ponderomotive force, Telluric currents, Terrestrial
magnetism, ampere-hours, Transverse waves, Longitudinal waves, Plane
waves, Refractive index, torque, Revolutions per minute, Photosphere,
Vortex, vortex rings,
permittivity, scalar product, vector product, tensor, divergent
series, linear operator, unit vector, parallelepiped, osculating
plane, standard candle
Solenoid, electro-magnets, Nicol prisms, rheostat, voltmeter,
gutta-percha covered wire, Electrical conductor, ammeters, Gramme
machine, binding posts, Induction motor,
Technological and industrial history of the United States, Western
Outline of energy development
Timeline of electromagnetism, Timeline of luminiferous aether
Citations and notes
^ Bruno Kolbe, Francis ed Legge, Joseph Skellon, tr., "An Introduction
to Electricity". Kegan Paul, Trench, Trübner, 1908. 429 pages. Page
391. (cf. "[...] high poles covered with copper plates and with gilded
tops were erected 'to break the stones coming from on high'. J.
Dümichen, Baugeschichte des Dendera-Tempels, Strassburg, 1877")
^ Urbanitzky, A. v., & Wormell, R. (1886).
Electricity in the
service of man: a popular and practical treatise on the applications
of electricity in modern life. London: Cassell &.
^ Lyons, T. A. (1901). A treatise on electromagnetic phenomena, and on
the compass and its deviations aboard ship. Mathematical, theoretical,
and practical. New York: J. Wiley & Sons.
^ Platonis Opera, Meyer and Zeller, 1839, p. 989.
^ The location of Magnesia is debated; it could be the region in
mainland Greece or Magnesia ad Sipylum. See, for example, "Magnet".
Language Hat blog. 28 May 2005. Retrieved 22 March 2013.
^ a b c Whittaker, E. T. (1910). A history of the theories of aether
and electricity from the age of Descartes to the close of the 19th
century. Dublin University Press series. London: Longmans, Green and
^ Carlson, John B. (1975) "
Lodestone Compass: Chinese or Olmec
Primacy?: Multidisciplinary analysis of an
Olmec hematite artifact
from San Lorenzo, Veracruz, Mexico", Science, 189 (4205 : 5
September), p. 753-760, doi:10.1126/science.189.4205.753. p. 753–760
Lodestone Compass: Chinese or
Olmec Primacy?: Multidisciplinary
analysis of an
Olmec hematite artifact from San Lorenzo, Veracruz,
Mexico - Carlson 189 (4205): 753 - Science
^ Li Shu-hua, p. 175
^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae
af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb
bc bd be bf Maver, William, Jr.: "Electricity, its History and
Progress", The Encyclopedia Americana; a library of universal
knowledge, vol. X, pp. 172ff. (1918). New York: Encyclopedia
^ Heinrich Karl Brugsch-Bey and Henry Danby Seymour, "A History of
Egypt Under the Pharaohs". J. Murray, 1881. Page 422. (cf. [... the
symbol of a] 'serpent' is rather a fish, which still serves, in the
Coptic language, to designate the electric fish [...])
^ Seeman, Bernard and Barry, James E. The Story of
Magnetism, Harvey House 1967, p. 19
^ Moller, Peter; Kramer, Bernd (December 1991), "Review: Electric
Fish", BioScience, American Institute of Biological Sciences, 41 (11):
794–6 , doi:10.2307/1311732, JSTOR 1311732
^ Bullock, Theodore H. (2005), Electroreception, Springer,
pp. 5–7, ISBN 0-387-23192-7
^ Morris, Simon C. (2003), Life's Solution: Inevitable Humans in a
Lonely Universe, Cambridge University Press, pp. 182–185,
^ Riddle of 'Baghdad's batteries'. BBC News.
^ After the Second World War, Willard Gray demonstrated current
production by a reconstruction of the inferred battery design when
filled with grape juice. W. Jansen experimented with 1,4-Benzoquinone
(some beetles produce quinones) and vinegar in a cell and got
^ An alternative, but still electrical explanation was offered by Paul
Keyser. It was suggested that a priest or healer, using an iron
spatula to compound a vinegar based potion in a copper vessel, may
have felt an electrical tingle and used the phenomenon either for
electro-acupuncture, or to amaze supplicants by electrifying a metal
^ Copper and iron form an electrochemical couple, so that in the
presence of any electrolyte, an electric potential (voltage) will be
produced. König had observed a number of very fine silver objects
Iraq which were plated with very thin layers of gold, and
speculated that they were electroplated using batteries of these
^ Corder, Gregory, "Using an Unconventional History of the Battery to
engage students and explore the importance of evidence", Virginia
Journal of Science Education 1
^ A history of electricity. By Park Benjamin. Pg 33
Epistola was written in 1269.
^ Lane, Frederic C. (1963) "The Economic Meaning of the Invention of
the Compass", The American Historical Review, 68 (3: April), p.
^ a b c Dampier, W. C. D. (1905). The theory of experimental
electricity. Cambridge physical series. Cambridge [Eng.: University
^ consult ' Priestley's 'History of Electricity,' London 1757
Robert Boyle (1675). Experiments and notes about the mechanical
origin or production of particular qualities.
^ Benjamin, P. (1895). A history of electricity: (The intellectual
rise in electricity) from antiquity to the days of Benjamin Franklin.
New York: J. Wiley & Sons.
^ Consult Boyle's 'Experiments on the Origin of Electricity,'" and
Priestley's 'History of Electricity'.
^ The Magnet, or Concerning
Magnetic Science (Magnes sive de arte
^ From Physico-Mechanical Experiments, 2nd Ed., London 1719
^ Consult Dr. Carpue's 'Introduction to
Electricity and Galvanism,'
^ Krebs, Robert E. (2003), Groundbreaking Scientific Experiments,
Inventions, and Discoveries of the 18th Century, Greenwood Publishing
Group, p. 82, ISBN 0-313-32015-2
^ a b Guarnieri, M. (2014). "
Electricity in the age of Enlightenment".
IEEE Industrial Electronics Magazine. 8 (3): 60–63.
^ Keithley, Joseph F. (1999), The Story of Electrical and Magnetic
Measurements: From 500 B.C. to the 1940s, Wiley,
^ Biography, Pieter (Petrus) van Musschenbroek
^ According to Priestley ('History of Electricity,' 3d ed., Vol. I, p.
^ Guarnieri, M. (2016). "The Rise of Light – Discovering Its
Secrets". Proc. IEEE. 104 (2): 467–473.
^ Priestley's 'History of Electricity,' p. 138
^ Catholic churchmen in science. (Second series) by James Joseph Wals.
^ The History and Present State of
Electricity with Original
Experiments By Joseph Priestle. Pg 173.
^ Cheney Hart: "Part of a letter from Cheney Hart, M.D. to William
Watson, F.R.S. giving Account of the Effects of
Electricity in the
County Hospital at Shrewsbury", Phil. Trans. 1753:48,
pp. 786–788. Read on November 14, 1754.
Kite Experiment (2011).
IEEE Global History Network.
^ see atmospheric electricity
^ Dr. Wall Experiments of the Luminous Qualities of Amber, Diamonds,
and Gum Lac, by Dr. Wall, in a Letter to Dr. Sloane, R. S. Secr. Phil.
Trans. 1708 26:69-76; doi:10.1098/rstl.1708.0011
^ Physico-mechanical experiments, on various subjects; with,
explanations of all the machines engraved on copper
^ Vail, A. (1845). The American electro magnetic telegraph: With the
reports of Congress, and a description of all telegraphs known,
employing electricity or galvanism. Philadelphia: Lea & Blanchard
^ Hutton, C., Shaw, G., Pearson, R., & Royal Society (Great
Britain). (1665). Philosophical transactions of the Royal Society of
London: From their commencement, in 1665 to the year 1800. London: C.
and R. Baldwin. PaGE 345.
^ Franklin, 'Experiments and Observations on Electricity'
^ Royal Society Papers, vol. IX (BL. Add MS 4440): Henry Elles, from
Lismore, Ireland, to the Royal Society, London, 9 August 1757, f.12b;
9 August 1757, f.166.
^ Tr., Test Theory of
Electricity and Magnetism
Philosophical Transactions 1771
^ Electric Telegraph, apparatus by wh. signals may be transmitted to a
distance by voltaic currents propagated on metallic wires; fnded. on
experimts. of Gray 1729, Nollet, Watson 1745, Lesage 1774, Lamond
1787, Reusserl794, Cavallo 1795, Betancourt 1795, Soemmering 1811,
Gauss & Weber 1834, &c. Telegraphs constructed by Wheatstone
& Independently by Steinheil 1837, improved by Morse, Cooke,
^ Cassell's miniature cyclopaedia By Sir William Laird Clowes. Page
^ Die Geschichte Der Physik in Grundzügen: th. In den letzten hundert
jahren (1780–1880) 1887-90 (tr. The history of physics in broad
terms: th. In the last hundred years (1780–1880) 1887-90) by
Ferdinand Rosenberger. F. Vieweg und sohn, 1890. Page 288.
^ a b Guarnieri, M. (2014). "The Big Jump from the Legs of a Frog".
IEEE Industrial Electronics Magazine. 8 (4): 59–61+69.
^ See Voltaic pile
^ 'Philosophical Transactions,' 1833
^ Of Torpedos Found on the Coast of England. In a Letter from John
Walsh, Esq; F. R. S. to Thomas Pennant, Esq; F. R. S. John Walsh
Philosophical Transactions Vol. 64, (1774), pp. 464-473
^ The works of Benjamin Franklin: containing several political and
historical tracts not included in any former ed., and many letters
official and private, not hitherto published; with notes and a life of
the author, Volume 6 Page 348.
^ another noted and careful experimenter in electricity and the
discoverer of palladium and rhodium
^ Philosophical Magazine, Vol. Ill, p. 211
^ 'Trans. Society of Arts,1 1825
^ Meteorological essays By François Arago, Sir Edward Sabine. Page
290. "On Rotation Magnetism. Proces verbal, Academy of Sciences, 22
^ For more, see Rotating magnetic field.
^ Tr., "The galvanic Circuit investigated mathematically".
^ G. S. Ohm (1827). Die galvanische Kette, mathematisch bearbeitet
(PDF). Berlin: T. H. Riemann.
^ The Encyclopedia Americana: a library of universal knowledge, 1918.
^ "A Brief History of Electromagnetism" (PDF).
^ "Electromagnetism". Smithsonian Institution Archives.
^ Tsverava, G. K. 1981. "FARADEI, GENRI, I OTKRYTIE INDUKTIROVANNYKH
TOKOV." Voprosy Istorii Estestvoznaniia i Tekhniki no. 3: 99-106.
Historical Abstracts, EBSCOhost . Retrieved October 17, 2009.
^ Bowers, Brian. 2004. "Barking Up the Wrong (Electric Motor) Tree."
Proceedings of the
IEEE 92, no. 2: 388-392. Computers & Applied
Sciences Complete, EBSCOhost . Retrieved October 17, 2009.
^ 1998. "Joseph Henry." Issues in Science & Technology 14, no. 3:
96. Associates Programs Source, EBSCOhost . Retrieved October 17,
^ According to Oliver Heaviside
^ Oliver Heaviside, Electromagnetic theory: Complete and unabridged
ed. of v.1, no.2, and: Volume 3. 1950.
^ Oliver Heaviside, Electromagnetic theory, v.1. "The Electrician"
printing and publishing company, limited, 1893.
^ A treatise on electricity, in theory and practice, Volume 1 By
Auguste de La Rive. Page 139.
^ 'Phil. Trans.,' 1845.
^ Elementary Lessons in
Magnetism By Silvanus Phillips
Thompson. Page 363.
^ Phil. Mag-., March 1854
^ Ronalds, B.F. (2016). Sir Francis Ronalds: Father of the Electric
Telegraph. London: Imperial College Press.
^ Ronalds, B.F. (2016). "Sir
Francis Ronalds and the Electric
Telegraph". Int. J. for the History of Engineering & Technology.
^ For more, see Counter-electromotive force.
^ Philosophical Magazine, 1849.
^ Ruhmkorff's version coil was such a success that in 1858 he was
awarded a 50,000-franc prize by
Napoleon III for the most important
discovery in the application of electricity.
^ American Academy of Arts and Sciences, Proceedings of the American
Academy of Arts and Sciences, Vol. XXIII, May 1895 - May 1896, Boston:
University Press, John Wilson and Son (1896), pp. 359-360: Ritchie's
most powerful version of his induction coil, using staged windings,
achieved electrical bolts 2 inches (5.1 cm) or longer in length.
^ Page, Charles G., History of Induction: The American Claim to the
Induction Coil and Its Electrostatic Developments, Boston: Harvard
University, Intelligencer Printing house (1867), pp. 104-106
^ American Academy, pp. 359-360
^ Lyons, T. A. (1901). A treatise on electromagnetic phenomena, and on
the compass and its deviations aboard ship. Mathematical, theoretical,
and practical. New York: J. Wiley & Sons. Page 500.
^ La, R. A. (1853). A treatise on electricity: In theory and practice.
London: Longman, Brown, Green, and Longmans.
^ tr., Introduction to electrostatics, the study of magnetism and
^ May be Johann Philipp Reis, of Friedrichsdorf, Germany
^ "On a permanent Deflection of the Galvanometer-needle under the
influence of a rapid series of equal and opposite induced Currents".
By Lord Rayleigh, F.R.S.. Philosophical magazine, 1877. Page 44.
^ Annales de chimie et de physique, Page 385. "Sur l'aimantation par
les courants" (tr. "On the magnetization by currents").
^ 'Ann. de Chimie III,' i, 385.
^ Jenkin, F. (1873).
Electricity and magnetism. Text-books of science.
London: Longmans, Green, and Co
^ Introduction to '
Electricity in the Service of Man'.
^ 'Poggendorf Ann.1 1851.
^ Proc. Am. Phil. Soc.,Vol. II, pp. 193
^ Annalen der Physik, Volume 103. Contributions to the acquaintance
with the electric spark, B. W. Feddersen. Page 69+.
Special information on method and apparatus can be found in
Feddersen's Inaugural Dissertation, Kiel 1857th (In the Commission der
Schwers'sehen Buchhandl Handl. In Kiel.)
^ Rowland, H. A. (1902). The physical papers of Henry Augustus
Rowland: Johns Hopkins University, 1876-1901. Baltimore: The Johns
^ LII. On the electromagnetic effect of convection-currents Henry A.
Rowland; Cary T. Hutchinson
Philosophical Magazine Series 5,
1941-5990, Volume 27, Issue 169, Pages 445 – 460
^ See electric machinery, electric direct current, electrical
^ consult his British patent of that year
^ consult 'Royal Society Proceedings, 1867 VOL. 10—12
^ RJ Gulcher, of Biala, near Bielitz, Austria.
^ The Electrical journal, Volume 7. 1881. Page117+
^ ETA: Electrical magazine: A. Ed, Volume 1
^ See electric direct current.
^ See Electric alternating current machinery.
^ The 19th century science book A Guide to the Scientific Knowledge of
Things Familiar provides a brief summary of scientific thinking in
this field at the time.
^ Consult Maxwell's '
Electricity and Magnetism,1 Vol. II, Chap. xx
^ On Faraday’s Lines of Force’ by
James Clerk Maxwell
James Clerk Maxwell 1855
^ James Clerk Maxwell, On Physical Lines of Force, Philosophical
^ In November 1847, Clerk Maxwell entered the University of Edinburgh,
learning mathematics from Kelland, natural philosophy from J. D.
Forbes, and logic from Sir W. R. Hamilton.
^ Glazebrook, R. (1896).
James Clerk Maxwell
James Clerk Maxwell and modern physics. New
York: Macmillan.Pg. 190
^ J J O'Connor and E F Robertson,
James Clerk Maxwell
James Clerk Maxwell Archived
2011-01-28 at the Wayback Machine., School of Mathematics and
Statistics, University of St Andrews, Scotland, November 1997
^ James Clerk Maxwell, A Dynamical Theory of the Electromagnetic
Philosophical Transactions of the
Royal Society of London
Royal Society of London 155,
^ Maxwell's '
Electricity and Magnetism,' preface
^ See oscillating current, telegraphy, wireless.
^ Proceedings of the London Mathematical Society, Volume 3. London
Mathematical Society, 1871. Pg. 224
Heinrich Hertz (1893). Electric Waves: Being Researches on the
Propagation of Electric Action with Finite Velocity Through Space.
^ Guarnieri, M. (2015). "How the Genie of Electronics Sprung Out".
IEEE Industrial Electronics Magazine. 9 (1): 77–79.
^ Crookes presented a lecture to the British Association for the
Advancement of Science, in Sheffield, on Friday, 22 August 1879 
^ consult 'Proc. British Association,' 1879
^ Perhaps there were other reasons than those mentioned for the
discontinuance. We do not dwell in the Palace of Truth.
^ in Sir W. Thomson's meaning of the word
Magnetic Theory. By Oliver HeaviBide. Vol. I. Electrician
Printing: and Publishing Company, Ltd. London, 1893
^ In mathematics, vectorial algebra may mean a linear algebra,
specifically the basic algebraic operations of vector addition and
scalar multiplication; see vector space. The algebraic operations in
vector calculus, namely the specific additional structure of vectors
displaystyle mathbf R ^ 3
of dot product and especially cross product. In this sense, vector
algebra is contrasted with geometric algebra, which provides an
alternative generalization to higher dimensions. Original vector
algebras of the 19th century like quaternions, tessarines, or
coquaternions, each of which has its own product. The vector algebras
biquaternions and hyperbolic quaternions can be used in special
^ Electrical engineer, Volume 18. Page299
^ Announced in his evening lecture to the
Royal Institution on Friday,
30 April 1897, and published in Philosophical Magazine, 44, 293 
^ Earl R. Hoover, Cradle of Greatness: National and World Achievements
of Ohio's Western Reserve (Cleveland: Shaker Savings Association,
^ Dayton C. Miller, "Ether-drift Experiments at Mount Wilson Solar
Observatory", Physical Review, S2, V19, N4, pp. 407-408 (April 1922).
^ Gordon gave four lectures on static electric induction (S. Low,
Marston, Searle, and Rivington, 1879). In 1891, he also published "A
treatise on electricity and magnetism]). Vol 1. Vol 2. (S. Low,
Marston, Searle & Rivington, limited).
^ Thompson, Silvanus P., Dynamo-Electric Machinery. pp. 17
^ Thompson, Silvanus P., Dynamo-Electric Machinery. pp. 16
^ See electric lighting
^ Giovanni Dosi, David J. Teece, Josef Chytry, Understanding
Industrial and Corporate Change, Oxford University Press, 2004, page
336. Google Books.
^ See telegraph
^ see transatlantic telegraph cable
^ Miller's '
Magnetism and Electricity,' p. 460
^ See Electric transmission of energy.
^ 'James Blyth - Britain's first modern wind power pioneer', by Trevor
Price, 2003, Wind Engineering, vol 29 no. 3, pp 191-200
^ [Anon, 1890, 'Mr. Brush's Windmill Dynamo', Scientific American, vol
63 no. 25, 20 December, p. 54]
^ A Wind Energy Pioneer:
Charles F. Brush
Charles F. Brush Archived 2008-09-08 at the
Wayback Machine., Danish Wind Industry Association. Retrieved
^ History of Wind Energy in Cutler J. Cleveland,(ed) Encyclopedia of
Energy Vol.6, Elsevier, ISBN 978-1-60119-433-6, 2007, pp. 421-422
^ See electrical units, electrical terms.
^ a b Miller 1981, Ch. 1
^ a b Pais 1982, Ch. 6b
^ a b c Janssen, 2007
^ Lorentz, Hendrik Antoon (1921), "Deux Mémoires de Henri Poincaré
sur la Physique Mathématique" [Two Papers of
Henri Poincaré on
Mathematical Physics], Acta Mathematica, 38 (1): 293–308,
^ Lorentz, H. A.; Lorentz, H. A. (1928), "Conference on the
Michelson-Morley Experiment", The Astrophysical Journal, 68:
345–351, Bibcode:1928ApJ....68..341M, doi:10.1086/143148
^ Galison 2002
^ Darrigol 2005
^ Katzir 2005
^ Miller 1981, Ch. 1.7 & 1.14
^ Pais 1982, Ch. 6 & 8
^ On the reception of relativity theory around the world, and the
different controversies it encountered, see the articles in Thomas F.
Glick, ed., The Comparative Reception of Relativity (Kluwer Academic
Publishers, 1987), ISBN 90-277-2498-9.
^ Pais, Abraham (1982), Subtle is the Lord. The Science and the Life
of Albert Einstein, Oxford University Press, pp. 382–386,
^ P. A. M. Dirac (1927). "The
Quantum Theory of the Emission and
Absorption of Radiation". Proceedings of the Royal Society of London
A. 114: 243–265. Bibcode:1927RSPSA.114..243D.
^ E. Fermi (1932). "
Quantum Theory of Radiation". Reviews of Modern
Physics. 4: 87–132. Bibcode:1932RvMP....4...87F.
^ F. Bloch; A. Nordsieck (1937). "Note on the Radiation Field of the
Electron". Physical Review. 52: 54–59. Bibcode:1937PhRv...52...54B.
^ V. F. Weisskopf (1939). "On the Self-Energy and the Electromagnetic
Field of the Electron". Physical Review. 56: 72–85.
^ R. Oppenheimer (1930). "Note on the Theory of the Interaction of
Field and Matter". Physical Review. 35: 461–477.
^ O. Hahn and F. Strassmann. Über den Nachweis und das Verhalten
der bei der Bestrahlung des Urans mittels Neutronen entstehenden
Erdalkalimetalle ("On the detection and characteristics of the
alkaline earth metals formed by irradiation of uranium with
Naturwissenschaften Volume 27, Number 1, 11–15
(1939). The authors were identified as being at the
Kaiser-Wilhelm-Institut für Chemie, Berlin-Dahlem. Received 22
Lise Meitner and O. R. Frisch. "Disintegration of
Neutrons: a New Type of Nuclear Reaction", Nature, Volume 143,
Number 3615, 239–240 (11 February 1939). The paper is dated 16
January 1939. Meitner is identified as being at the Physical
Institute, Academy of Sciences, Stockholm. Frisch is identified as
being at the Institute of Theoretical Physics, University of
^ O. R. Frisch. "Physical Evidence for the Division of Heavy Nuclei
under Neutron Bombardment", Nature, Volume 143, Number 3616,
276–276 (18 February 1939) Archived 2009-01-23 at the Wayback
Machine.. The paper is dated 17 January 1939. [The experiment for
this letter to the editor was conducted on 13 January 1939; see
Richard Rhodes The Making of the Atomic Bomb. 263 and 268 (Simon and
^ Ruth Lewin Sime. From Exceptional Prominence to Prominent Exception:
Lise Meitner at the Kaiser Wilhelm Institute for Chemistry Ergebnisse
24 Forschungsprogramm Geschichte der Kaiser-Wilhelm-Gesellschaft im
^ Ruth Lewin Sime. Lise Meitner: A Life in Physics (University of
^ Elisabeth Crawford, Ruth Lewin Sime, and Mark Walker. "A Nobel Tale
of Postwar Injustice", Physics Today Volume 50, Issue 9,
^ W. E. Lamb; R. C. Retherford (1947). "Fine Structure of the Hydrogen
Atom by a
Microwave Method,". Physical Review. 72: 241–243.
^ P. Kusch; H. M. Foley (1948). "On the Intrinsic Moment of the
Electron". Physical Review. 73: 412. Bibcode:1948PhRv...73..412F.
^ Brattain quoted in Michael Riordan and Lillian Hoddeson; Crystal
Fire: The Invention of the Transistor and the Birth of the Information
Age. New York: Norton (1997) ISBN 0-393-31851-6 pbk. p. 127
^ Schweber, Silvan (1994). "Chapter 5". QED and the Men Who Did it:
Dyson, Feynman, Schwinger, and Tomonaga. Princeton University Press.
p. 230. ISBN 978-0-691-03327-3.
^ H. Bethe (1947). "The Electromagnetic Shift of Energy Levels".
Physical Review. 72: 339–341. Bibcode:1947PhRv...72..339B.
^ S. Tomonaga (1946). "On a Relativistically Invariant Formulation of
Quantum Theory of Wave Fields". Progress of Theoretical Physics.
1: 27–42. doi:10.1143/PTP.1.27.
^ J. Schwinger (1948). "On Quantum-
Electrodynamics and the Magnetic
Moment of the Electron". Physical Review. 73: 416–417.
^ J. Schwinger (1948). "
Quantum Electrodynamics. I. A Covariant
Formulation". Physical Review. 74: 1439–1461.
^ R. P. Feynman (1949). "Space-Time Approach to Quantum
Electrodynamics". Physical Review. 76: 769–789.
^ R. P. Feynman (1949). "The Theory of Positrons". Physical Review.
76: 749–759. Bibcode:1949PhRv...76..749F.
^ R. P. Feynman (1950). "Mathematical Formulation of the Quantum
Theory of Electromagnetic Interaction". Physical Review. 80:
^ a b F. Dyson (1949). "The Radiation Theories of Tomonaga, Schwinger,
and Feynman". Physical Review. 75: 486–502.
^ F. Dyson (1949). "The S Matrix in
Quantum Electrodynamics". Physical
Review. 75: 1736–1755. Bibcode:1949PhRv...75.1736D.
Nobel Prize in Physics 1965". Nobel Foundation. Retrieved
^ Feynman, Richard (1985). QED: The Strange Theory of Light and
Matter. Princeton University Press. p. 128.
^ Kurt Lehovec's patent on the isolation p-n junction: U.S. Patent
3,029,366 granted on April 10, 1962, filed April 22, 1959. Robert
Noyce credits Lehovec in his article – "Microelectronics",
Scientific American, September 1977, Volume 23, Number 3, pp. 63–9.
^ The Chip that Jack Built, (c. 2008), (HTML), Texas Instruments,
accessed May 29, 2008.
^ Winston, Brian. Media technology and society: a history: from the
telegraph to the Internet, (1998), Routeledge, London,
ISBN 0-415-14230-X ISBN 978-0-415-14230-4, p. 221
^ Nobel Web AB, (October 10, 2000),(The
Nobel Prize in Physics 2000,
Retrieved on May 29, 2008
^ Cartlidge, Edwin. "The Secret World of Amateur Fusion". Physics
World, March 2007: IOP Publishing Ltd, pp. 10-11. ISSN 0953-8585.
^ R. Nave. "Parity". HyperPhysics/Georgia State University.
^ "Reversal of the Parity Conservation Law in Nuclear Physics" (PDF).
^ "Parity is not conserved!". Caltech/The Feynman Lectures.
^ S.L. Glashow (1961). "Partial-symmetries of weak interactions".
Nuclear Physics. 22: 579–588. Bibcode:1961NucPh..22..579G.
^ S. Weinberg (1967). "A Model of Leptons".
Physical Review Letters.
19: 1264–1266. Bibcode:1967PhRvL..19.1264W.
^ A. Salam (1968). N. Svartholm, ed. Elementary Particle Physics:
Relativistic Groups and Analyticity. Eighth Nobel Symposium.
Stockholm: Almquvist and Wiksell. p. 367.
^ F. Englert; R. Brout (1964). "Broken Symmetry and the
Mass of Gauge
Physical Review Letters. 13: 321–323.
^ P. W. Higgs (1964). "Broken Symmetries and the Masses of Gauge
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^ A long conductor attached to an object.
^ It is noted that though not all space tethers are conductive.
^ A medical imaging technique used in radiology to visualize detailed
internal structures. The good contrast it provides between the
different soft tissues of the body make it especially useful in brain,
muscles, heart, and cancer compared with other medical imaging
techniques such as computed tomography (CT) or X-rays.
Wireless power is the transmission of electrical energy from a power
source to an electrical load without interconnecting wires. Wireless
transmission is useful in cases where interconnecting wires are
inconvenient, hazardous, or impossible.
Wireless electricity could power consumer, industrial electronics".
MIT News. 2006-11-14.
^ "Goodbye wires…".
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^ M-Theory: The Mother of all SuperStrings
^ Hawking, Stephen. Gödel and the end of physics, July 20, 2002.
^ A hypothetical particle in particle physics that is a magnet with
only one magnetic pole. In more technical terms, a magnetic monopole
would have a net "magnetic charge". Modern interest in the concept
stems from particle theories, notably the grand unification and
superstring theories, which predict their existence. See Particle Data
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