Transcriber’s Notes
In this Plain Text version of this eBook, italics are enclosed within
~tildas~, superscripts and subscripts are enclosed in curly braces and
preceded by a caret ^{superscript} or an underscore _{subscript}.
Other notes will be found at the end of this eBook.
SMITHSONIAN MISCELLANEOUS COLLECTIONS
VOLUME 76, NUMBER 2
HISTORY OF ELECTRIC LIGHT
BY
HENRY SCHROEDER
Harrison, New Jersey
[Illustration: FOR THE INCREASE
AND DIFFVSION OF
KNOWLEDGE AMONG MEN
SMITHSONIAN
INSTITVTION
WASHINGTON 1846]
(PUBLICATION 2717)
CITY OF WASHINGTON
PUBLISHED BY THE SMITHSONIAN INSTITUTION
AUGUST 15, 1923
The Lord Baltimore Press
BALTIMORE, MD., U. S. A.
CONTENTS
PAGE
List of Illustrations v
Foreword ix
Chronology of Electric Light xi
Early Records of Electricity and Magnetism 1
Machines Generating Electricity by Friction 2
The Leyden Jar 3
Electricity Generated by Chemical Means 3
Improvement of Volta’s Battery 5
Davy’s Discoveries 5
Researches of Oersted, Ampère, Schweigger and Sturgeon 6
Ohm’s Law 7
Invention of the Dynamo 7
Daniell’s Battery 10
Grove’s Battery 11
Grove’s Demonstration of Incandescent Lighting 12
Grenet Battery 13
De Moleyns’ Incandescent Lamp 13
Early Developments of the Arc Lamp 14
Joule’s Law 16
Starr’s Incandescent Lamp 17
Other Early Incandescent Lamps 19
Further Arc Lamp Developments 20
Development of the Dynamo, 1840–1860 24
The First Commercial Installation of an Electric Light 25
Further Dynamo Developments 27
Russian Incandescent Lamp Inventors 30
The Jablochkoff “Candle” 31
Commercial Introduction of the Differentially Controlled Arc Lamp 33
Arc Lighting in the United States 33
Other American Arc Light Systems 40
“Sub-Dividing the Electric Light” 42
Edison’s Invention of a Practical Incandescent Lamp 43
Edison’s Three-Wire System 53
Development of the Alternating Current Constant Potential System 54
Incandescent Lamp Developments, 1884–1894 56
The Edison “Municipal” Street Lighting System 62
The Shunt Box System for Series Incandescent Lamps 64
The Enclosed Arc Lamp 65
The Flame Arc Lamp 67
The Constant Current Transformer for Series Circuits 69
Enclosed Series Alternating Current Arc Lamps 69
Series Incandescent Lamps on Constant Current Transformers 70
The Nernst Lamp 71
The Cooper-Hewitt Lamp 72
The Luminous or Magnetite Arc Lamp 74
Mercury Arc Rectifier for Magnetite Arc Lamps 77
Incandescent Lamp Developments, 1894–1904 78
The Moore Tube Light 79
The Osmium Lamp 82
The Gem Lamp 82
The Tantalum Lamp 84
Invention of the Tungsten Lamp 85
Drawn Tungsten Wire 87
The Quartz Mercury Vapor Arc Lamp 88
The Gas-Filled Tungsten Lamp 89
Types and Sizes of Tungsten Lamps Now Made 91
Standard Voltages 93
Cost of Incandescent Electric Light 93
Statistics Regarding the Present Demand for Lamps 94
Selected Bibliography 95
LIST OF ILLUSTRATIONS
PAGE
Portion of the Electrical Exhibit in the United States National
Museum viii
Otto Von Guericke’s Electric Machine, 1650 2
Voltaic Pile, 1799 4
Faraday’s Dynamo, 1831 8
Pixii’s Dynamo, 1832 9
Daniell’s Cell, 1836 10
Grove’s Cell, 1838 11
Grove’s Incandescent Lamp, 1840 13
De Moleyns’ Incandescent Lamp, 1841 14
Wright’s Arc Lamp, 1845 15
Archereau’s Arc Lamp, 1848 16
Starr’s Incandescent Lamp, 1845 18
Staite’s Incandescent Lamp, 1848 19
Roberts’ Incandescent Lamp, 1852 19
Farmer’s Incandescent Lamp, 1859 20
Roberts’ Arc Lamp, 1852 21
Slater and Watson’s Arc Lamp, 1852 21
Diagram of “Differential” Method of Control of an Arc Lamp 22
Lacassagne and Thiers’ Differentially Controlled Arc Lamp, 1856 23
Serrin’s Arc Lamp, 1857 24
Siemens’ Dynamo, 1856 25
Alliance Dynamo, 1862 26
Wheatstone’s Self-Excited Dynamo, 1866 27
Gramme’s Dynamo, 1871 28
Gramme’s “Ring” Armature 28
Alteneck’s Dynamo with “Drum” Wound Armature, 1872 29
Lodyguine’s Incandescent Lamp, 1872 30
Konn’s Incandescent Lamp, 1875 30
Bouliguine’s Incandescent Lamp, 1876 31
Jablochkoff “Candle,” 1876 32
Jablochkoff’s Alternating Current Dynamo, 1876 33
Wallace-Farmer Arc Lamp, 1875 34
Wallace-Farmer Dynamo, 1875 34
Weston’s Arc Lamp, 1876 35
Brush’s Dynamo, 1877 36
Diagram of Brush Armature 36
Brush’s Arc Lamp, 1877 37
Thomson-Houston Arc Dynamo, 1878 38
Diagram of T-H Arc Lighting System 39
Thomson-Houston Arc Lamp, 1878 40
Thomson Double Carbon Arc Lamp 40
Maxim Dynamo 41
Sawyer’s Incandescent Lamp, 1878 42
Farmer’s Incandescent Lamp, 1878 42
Maxim’s Incandescent Lamp, 1878 43
Edison’s First Experimental Lamp, 1878 44
Diagram of Constant Current Series System 45
Diagram of Edison’s Multiple System, 1879 45
Edison Dynamo, 1879 46
Edison’s High Resistance Platinum Lamp, 1879 47
Edison’s High Resistance Platinum in Vacuum Lamp, 1879 47
Edison’s Carbon Lamp of October 21, 1879 48
Demonstration of Edison’s Incandescent Lighting System 49
Dynamo Room, S. S. Columbia 50
Original Socket for Incandescent Lamps 51
Wire Terminal Base Lamp, 1880 51
Original Screw Base Lamp, 1880 52
Improved Screw Base Lamp, 1881 52
Final Form of Screw Base, 1881 53
Diagram of Edison’s Three Wire System, 1881 54
Diagram of Stanley’s Alternating Current Multiple System, 1885 55
Standard Edison Lamp, 1884 56
Standard Edison Lamp, 1888 56
Standard Edison Lamp, 1894 57
Various Bases in Use, 1892 58
Thomson-Houston Socket 59
Westinghouse Socket 59
Adapters for Edison Screw Sockets, 1892 60
Various Series Bases in Use, 1892 61
Edison “Municipal” System, 1885 62
Edison “Municipal” Lamp, 1885 63
Shunt Box System, 1887 64
Enclosed Arc Lamp, 1893 65
Open Flame Arc Lamp, 1898 66
Enclosed Flame Arc Lamp, 1908 66
Constant Current Transformer, 1900 68
Series Incandescent Lamp Socket with Film Cutout, 1900 70
Nernst Lamp, 1900 71
Diagram of Nernst Lamp 72
Cooper-Hewitt Mercury Vapor Arc Lamp, 1901 73
Diagram of Cooper-Hewitt Lamp for Use on Alternating Current 74
Luminous or Magnetite Arc Lamp, 1902 75
Diagram of Series Magnetite Arc Lamp 76
Mercury Arc Rectifier Tube for Series Magnetite Arc Circuits, 1902 77
Early Mercury Arc Rectifier Installation 78
The Moore Tube Light, 1904 79
Diagram of Feeder Valve of Moore Tube 80
Osmium Lamp, 1905 82
Gem Lamp, 1905 83
Tantalum Lamp, 1906 84
Tungsten Lamp, 1907 86
Drawn Tungsten Wire Lamp, 1911 87
Quartz Mercury Vapor Lamp, 1912 88
Gas Filled Tungsten Lamp, 1913 89
Gas Filled Tungsten Lamp, 1923 90
Standard Tungsten Lamps, 1923 92
[Illustration: PORTION OF THE ELECTRICAL EXHIBIT IN THE UNITED STATES
NATIONAL MUSEUM.
Section devoted to the historical development of the electric light and
dynamo.]
FOREWORD
In the year 1884 a Section of Transportation was organized in the
United States National Museum for the purpose of preparing and
assembling educational exhibits of a few objects of railroad machinery
which had been obtained both from the Centennial Exhibition held in
Philadelphia in 1876 and still earlier as incidentals to ethnological
collections, and to secure other collections relating to the railway
industry.
From this beginning the section was expanded to include the whole
field of engineering and is designated at present as the Divisions of
Mineral and Mechanical Technology. The growth and enlargement of the
collections has been particularly marked in the fields of mining and
mineral industries; mechanical engineering, especially pertaining to
the steam engine, internal combustion engine and locomotive; naval
architecture, and electrical engineering, particularly the development
of the telegraph, telephone and the electric light.
In the acquisition of objects visualizing the history of electric
light the Museum has been rather fortunate, particularly as regards
the developments in the United States. Thus mention may be made of
the original Patent Office models of the more important dynamos, arc
lights and incandescent lights, together with original commercial
apparatus after these models; a unit of the equipment used in the
first commercially successful installation on land of an incandescent
lighting system, presented by Joseph E. Hinds in whose engraving
establishment in New York City the installation was made in 1881; and
a large series of incandescent lights, mainly originals, visualizing
chronologically the developments of the Edison light from its
inception, presented at intervals since the year 1898 by the General
Electric Company.
The object of all collections in the Divisions is to visualize
broadly the steps by which advances have been made in each field of
engineering; to show the layman the fundamental and general principles
which are the basis for the developments; and to familiarize the
engineer with branches of engineering other than his own. Normally
when a subject is completely covered by a collection of objects, a
paper is prepared and published describing the collection and the
story it portrays. In the present instance, however, on account of
the uncertainty of the time of completing the collection, if it is
possible ever to bring this about, it was thought advisable to publish
Mr. Schroeder’s paper which draws upon the Museum collection as
completely as possible.
CARL W. MITMAN,
~Curator, Divisions of Mineral and
Mechanical Technology,
U. S. National Museum~.
CHRONOLOGY OF ELECTRIC LIGHT
1800--Allesandro Volta demonstrated his discovery that electricity
can be generated by chemical means. The VOLT, the unit of
electric pressure, is named in his honor for this discovery
of the electric battery.
1802--Sir Humphry Davy demonstrated that electric current can heat
carbon and strips of metal to incandescence and give light.
1809--Sir Humphry Davy demonstrated that current will give a
brilliant flame between the ends of two carbon pencils
which are first allowed to touch each other and then pulled
apart. This light he called the “arc” on account of its
arch shape.
1820--André Marie Ampère discovered that current flowing through
a coiled wire gives it the properties of a magnet. The
AMPERE, the unit of flow of electric current, is named in
his honor for this discovery.
1825--Georg Simon Ohm discovered the relation between the voltage,
ampereage and resistance in an electric circuit, which is
called Ohm’s Law. The OHM, the unit of electric resistance,
is named in his honor for this discovery.
1831--Michael Faraday discovered that electricity can be generated
by moving a wire in the neighborhood of a magnet, the
principle of the dynamo.
1840--Sir William Robert Grove demonstrated his experimental
incandescent lamp in which platinum is made incandescent by
current flowing through it.
1841--Frederick De Moleyns obtained the first patent on an
incandescent lamp. The burner was powdered charcoal
operating in an exhausted glass globe.
1845--Thomas Wright obtained the first patent on an arc light.
1845--J. W. Starr invented an incandescent lamp consisting of a
carbon pencil operating in the vacuum above a column of
mercury.
1856--Joseph Lacassagne and Henry Thiers invented the
“differential” method of control of the arc which was
universally used twenty years later when the arc lamp was
commercially established.
1862--The first commercial installation of an electric light. An
arc light was put in a lighthouse in England.
1866--Sir Charles Wheatstone invented the “self-excited” dynamo,
now universally used.
1872--Lodyguine invented an incandescent lamp having a graphite
burner operating in nitrogen gas.
1876--Paul Jablochkoff invented the “electric candle,” an arc light
commercially used for lighting the boulevards in Paris.
1877–8--Arc light systems commercially established in the United
States by William Wallace and Prof. Moses Farmer, Edward
Weston, Charles F. Brush and Prof. Elihu Thomson and Edwin
J. Houston.
1879--Thomas Alva Edison invented an incandescent lamp consisting
of a high resistance carbon filament operating in a
high vacuum maintained by an all glass globe. These
principles are used in all incandescent lamps made today.
He also invented a completely new system of distributing
electricity at constant pressure, now universally used.
1882--Lucien Goulard and John D. Gibbs invented a series
alternating current system of distributing electric
current. This has not been commercially used.
1886--William Stanley invented a constant pressure alternating
current system of distribution. This is universally used
where current is to be distributed long distances.
1893--Louis B. Marks invented the enclosed carbon arc lamp.
1898--Bremer’s invention of the flame arc lamp, having carbons
impregnated with various salts, commercially established.
1900--Dr. Walther Nernst’s invention of the Nernst lamp
commercially established. The burner consisted of various
oxides, such as zirconia, which operated in the open air.
1901--Dr. Peter Cooper Hewitt’s invention of the mercury arc light
commercially established.
1902--The magnetite arc lamp was developed by C. A. B. Halvorson,
Jr. This has a new method of control of the arc. The
negative electrode consists of a mixture of magnetite and
other substances packed in an iron tube.
1904--D. McFarlan Moore’s invention of the Moore vacuum tube light
commercially established. This consisted of a long tube,
made in lengths up to 200 feet, from which the air had been
exhausted to about a thousandth of an atmosphere. High
voltage current passing through this rarefied atmosphere
caused it to glow. Rarefied carbon dioxide gas was later
used.
1905--Dr. Auer von Welsbach’s invention of the osmium incandescent
lamp commercially established, but only on a small scale
in Europe. The metal osmium, used for the filament which
operated in vacuum, is rarer and more expensive than
platinum.
1905--Dr. Willis R. Whitney’s invention of the Gem incandescent
lamp commercially established. The carbon filament had been
heated to a very high temperature in an electric resistance
furnace invented by him. The lamp was 25 per cent more
efficient than the regular carbon lamp.
1906--Dr. Werner von Bolton’s invention of the tantalum
incandescent lamp commercially established.
1907--Alexander Just and Franz Hanaman’s invention of the tungsten
filament incandescent lamp commercially established.
1911--Dr. William D. Coolidge’s invention of drawn tungsten wire
commercially established.
1913--Dr. Irving Langmuir’s invention of the gas-filled tungsten
filament incandescent lamp commercially established.
HISTORY OF ELECTRIC LIGHT
BY HENRY SCHROEDER,
HARRISON, NEW JERSEY.
EARLY RECORDS OF ELECTRICITY AND MAGNETISM
About twenty-five centuries ago, Thales, a Greek philosopher, recorded
the fact that if amber is rubbed it will attract light objects.
The Greeks called amber “elektron,” from which we get the word
“electricity.” About two hundred and fifty years later, Aristotle,
another Greek philosopher, mentioned that the lodestone would attract
iron. Lodestone is an iron ore (Fe_{3}O_{4}), having magnetic qualities
and is now called magnetite. The word “magnet” comes from the fact that
the best specimens of lodestones came from Magnesia, a city in Asia
Minor. Plutarch, a Greek biographer, wrote about 100 A. D., that iron
is sometimes attracted and at other times repelled by a lodestone. This
indicates that the piece of iron was magnetised by the lodestone.
In 1180, Alexander Neckham, an English Monk, described the compass,
which probably had been invented by sailors of the northern countries
of Europe, although its invention has been credited to the Chinese.
Early compasses probably consisted of an iron needle, magnetised by
a lodestone, mounted on a piece of wood floating in water. The word
lodestone or “leading stone” comes from the fact that it would point
towards the north if suspended like a compass.
William Gilbert, physician to Queen Elizabeth of England, wrote a
book about the year 1600 giving all the information then known on
the subject. He also described his experiments, showing, among other
things, the existence of magnetic lines of force and of north and south
poles in a magnet. Robert Norman had discovered a few years previously
that a compass needle mounted on a horizontal axis would dip downward.
Gilbert cut a large lodestone into a sphere, and observed that the
needle did not dip at the equator of this sphere, the dip increasing
to 90 degrees as the poles were approached. From this he deduced that
the earth was a magnet with the magnetic north pole at the geographic
north pole. It has since been determined that these two poles do not
coincide. Gilbert suggested the use of the dipping needle to determine
latitude. He also discovered that other substances, beside amber, would
attract light objects if rubbed.
MACHINES GENERATING ELECTRICITY BY FRICTION
Otto Von Guericke was mayor of the city of Magdeburg as well as a
philosopher. About 1650 he made a machine consisting of a ball of
sulphur mounted on a shaft which could be rotated. Electricity was
generated when the hand was pressed against the globe as it rotated.
He also discovered that electricity could be conducted away from the
globe by a chain and would appear at the other end of the chain. Von
Guericke also invented the vacuum air pump. In 1709, Francis Hawksbee,
an Englishman, made a similar machine, using a hollow glass globe which
could be exhausted. The exhausted globe when rotated at high speed and
rubbed by hand would produce a glowing light. This “electric light” as
it was called, created great excitement when it was shown before the
Royal Society, a gathering of scientists, in London.
[Illustration: OTTO VON GUERICKE’S ELECTRIC MACHINE, 1650.
A ball of sulphur was rotated, electricity being generated when it
rubbed against the hand.]
Stephen Gray, twenty years later, showed the Royal Society that
electricity could be conducted about a thousand feet by a hemp thread,
supported by silk threads. If metal supports were used, this could not
be done. Charles du Fay, a Frenchman, repeated Gray’s experiments,
and showed in 1733 that the substances which were insulators, and
which Gilbert had discovered, would become electrified if rubbed.
Those substances which Gilbert could not electrify were conductors of
electricity.
THE LEYDEN JAR
The thought came to Von Kleist, Bishop of Pomerania, Germany, about
1745, that electricity could be stored. The frictional machines
generated so small an amount of electricity (though, as is now known,
at a very high pressure--several thousand volts) that he thought he
could increase the quantity by storing it. Knowing that glass was
an insulator and water a conductor, he filled a glass bottle partly
full of water with a nail in the cork to connect the machine with the
water. Holding the bottle in one hand and turning the machine with
the other for a few minutes, he then disconnected the bottle from the
machine. When he touched the nail with his other hand he received a
shock which nearly stunned him. This was called the Leyden jar, the
forerunner of the present condenser. It received its name from the fact
that its discovery was also made a short time after by experimenters
in the University of Leyden. Further experiments showed that the hand
holding the bottle was as essential as the water inside, so these were
substituted by tin foil coatings inside and outside the bottle.
Benjamin Franklin, American statesman, scientist and printer, made
numerous experiments with the Leyden jar. He connected several jars
in parallel, as he called it, which gave a discharge strong enough to
kill a turkey. He also connected the jars in series, or “in cascade” as
he called it, thus establishing the principle of parallel and series
connections. Noticing the similarity between the electric spark and
lightning, Franklin in 1752, performed his famous kite experiment.
Flying a kite in a thunderstorm, he drew electricity from the clouds to
charge Leyden jars, which were later discharged, proving that lightning
and electricity were the same. This led him to invent the lightning rod.
ELECTRICITY GENERATED BY CHEMICAL MEANS
Luigi Galvani was an Italian scientist. About 1785, so the story goes,
his wife was in delicate health, and some frog legs were being skinned
to make her a nourishing soup. An assistant holding the legs with a
metal clamp and cutting the skin with a scalpel, happened to let the
clamp and scalpel touch each other. To his amazement the frog legs
twitched. Galvani repeated the experiment many times by touching
the nerve with a metal rod and the muscle with a different metal rod
and allowing the rods to touch, and propounded the theory of animal
electricity in a paper he published in 1791.
Allesandro Volta, a professor of physics in the University of Pavia,
Italy, read about Galvani’s work and repeated his experiments. He
found that the extent of the movement of the frog legs depended on the
metals used for the rods, and thus believed that the electric charge
was produced by the contact of dissimilar metals with the moisture in
the muscles. To prove his point he made a pile of silver and zinc discs
with cloths, wet with salt water, between them. This was in 1799, and
he described his pile in March, 1800, in a letter to the Royal Society
in London.
[Illustration: VOLTAIC PILE, 1799.
Volta discovered that electricity could be generated by chemical means
and made a pile of silver and zinc discs with cloths, wet with salt
water, between them. This was the forerunner of the present-day dry
battery. Photograph courtesy Prof. Chas. F. Chandler Museum, Columbia
University, New York.]
This was an epoch-making discovery as it was the forerunner of the
present-day primary battery. Volta soon found that the generation of
electricity became weaker as the cloths became dry, so to overcome
this he made his “crown of cups.” This consisted of a series of cups
containing salt water in which strips of silver and zinc were dipped.
Each strip of silver in one cup was connected to the zinc strip in
the next cup, the end strips of silver and zinc being terminals of
the battery. This was the first time that a continuous supply of
electricity in reasonable quantities was made available, so the VOLT,
the unit of electrical pressure was named in his honor. It was later
shown that the chemical affinity of one of the metals in the liquid was
converted into electric energy. The chemical action of Volta’s battery
is that the salt water attacks the zinc when the circuit is closed
forming zinc chloride, caustic soda and hydrogen gas. The chemical
equation is:
Zn + 2NaCl + 2H_{2}O = ZnCl_{2} + 2NaOH + H_{2}
IMPROVEMENT OF VOLTA’S BATTERY
It was early suggested that sheets of silver and zinc be soldered
together back to back and that a trough be divided into cells by these
bimetal sheets being put into grooves cut in the sides and bottom of
the trough. This is the reason why one unit of a battery is called a
“cell.” It was soon found that a more powerful cell could be made if
copper, zinc and dilute sulphuric acid were used. The zinc is dissolved
by the acid forming zinc sulphate and hydrogen gas, thus:
Zn + H_{2}SO_{4} = ZnSO_{4} + H_{2}
The hydrogen gas appears as bubbles on the copper and reduces the open
circuit voltage (about 0.8 volt per cell) as current is taken from the
battery. This is called “polarization.” Owing to minute impurities in
the zinc, it is attacked by the acid even when no current is taken from
the battery, the impurities forming with the zinc a short circuited
local cell. This is called “local action,” and this difficulty was at
first overcome by removing the zinc from the acid when the battery was
not in use.
DAVY’S DISCOVERIES
Sir Humphry Davy was a well-known English chemist, and with the aid of
powerful batteries constructed for the Royal Institution in London,
he made numerous experiments on the chemical effects of electricity.
He decomposed a number of substances and discovered the elements
boron, potassium and sodium. He heated strips of various metals to
incandescence by passing current through them, and showed that platinum
would stay incandescent for some time without oxidizing. This was about
1802.
In the early frictional machines, the presence of electricity was shown
by the fact that sparks could be obtained. Similarly the breaking
of the circuit of a battery would give a spark. Davy, about 1809,
demonstrated that this spark could be maintained for a long time with
the large battery of 2000 cells he had had constructed. Using two
sticks of charcoal connected by wires to the terminals of this very
powerful battery, he demonstrated before the Royal Society the light
produced by touching the sticks together and then holding them apart
horizontally about three inches. The brilliant flame obtained he called
an “arc” because of its arch shape, the heated gases, rising, assuming
this form. Davy was given the degree of LL. D. for his distinguished
research work, and was knighted on the eve of his marriage, April 11,
1812.
RESEARCHES OF OERSTED, AMPÈRE, SCHWEIGGER AND STURGEON
Hans Christian Oersted was a professor of physics at the University of
Copenhagen in Denmark. One day in 1819, while addressing his students,
he happened to hold a wire, through which current was flowing, over
a large compass. To his surprise he saw the compass was deflected
from its true position. He promptly made a number of experiments and
discovered that by reversing the current the compass was deflected in
the opposite direction. Oersted announced his discovery in 1820.
André Marie Ampère was a professor of mathematics in the Ecole
Polytechnic in Paris. Hearing of Oersted’s discovery, he immediately
made some experiments and made the further discovery in 1820 that if
the wire is coiled and current passed through it, the coil had all the
properties of a magnet.
These two discoveries led to the invention of Schweigger in 1820,
of the galvanometer (or “multiplier” as it was then called), a very
sensitive instrument for measuring electric currents. It consisted of
a delicate compass needle suspended in a coil of many turns of wire.
Current in the coil deflected the needle, the direction and amount of
deflection indicating the direction and strength of the current. Ampère
further made the discovery that currents in opposite directions repel
and in the same directions attract each other. He also gave a rule
for determining the direction of the current by the deflection of the
compass needle. He developed the theory that magnetism is caused by
electricity flowing around the circumference of the body magnetised.
The AMPERE, the unit of flow of electric current, was named in honor of
his discoveries.
In 1825 it was shown by Sturgeon that if a bar of iron were placed in
the coil, its magnetic strength would be very greatly increased, which
he called an electro-magnet.
OHM’S LAW
Georg Simon Ohm was born in Bavaria, the oldest son of a poor
blacksmith. With the aid of friends he went to college and became a
teacher. It had been shown that the rate of transfer of heat from one
end to the other of a metal bar is proportional to the difference
of temperature between the ends. About 1825, Ohm, by analogy and
experiment, found that the current in a conductor is proportional to
the difference of electric pressure (voltage) between its ends. He
further showed that with a given difference of voltage, the current
in different conductors is inversely proportional to the resistance
of the conductor. Ohm therefore propounded the law that the current
flowing in a circuit is equal to the voltage on that circuit divided by
the resistance of the circuit. In honor of this discovery, the unit of
electrical resistance is called the OHM. This law is usually expressed
as:
C = E/R
“C” meaning current (in amperes), “E” meaning electromotive force or
voltage (in volts) and “R” meaning resistance (in ohms).
This is one of the fundamental laws of electricity and if thoroughly
understood, will solve many electrical problems. Thus, if any two of
the above units are known, the third can be determined. Examples: An
incandescent lamp on a 120-volt circuit consumes 0.4 ampere, hence its
resistance under such conditions is 300 ohms. Several trolley cars at
the end of a line take 100 amperes to run them and the resistance of
the overhead wire from the power house to the trolley cars is half
an ohm; the drop in voltage on the line between the power house and
trolley cars is therefore 50 volts, so that if the voltage at the power
house were 600, it would be 550 volts at the end of the line.
Critics derided Ohm’s law so that he was forced out of his position
as teacher in the High School in Cologne. Finally after ten years Ohm
began to find supporters and in 1841 his law was publicly recognized by
the Royal Society of London which presented him with the Copley medal.
INVENTION OF THE DYNAMO
Michael Faraday was an English scientist. Born of parents in poor
circumstances, he became a bookbinder and studied books on electricity
and chemistry. He finally obtained a position as laboratory assistant
to Sir Humphry Davy helping him with his lectures and experiments. He
also made a number of experiments himself and succeeded in liquifying
chlorine gas for which he was elected to a Fellowship in the Royal
Institution in 1824. Following up Oersted’s and Ampère’s work, he
endeavored to find the relation between electricity and magnetism.
Finally on Oct. 17, 1831, he made the experiment of moving a permanent
bar magnet in and out of a coil of wire connected to a galvanometer.
This generated electricity in the coil which deflected the galvanometer
needle. A few days after, Oct. 28, 1831, he mounted a copper disk
on a shaft so that the disk could be rotated between the poles of
a permanent horseshoe magnet. The shaft and edge of the disk were
connected by brushes and wires to a galvanometer, the needle of which
was deflected as the disk was rotated. A paper on his invention was
read before the Royal Society on November 24, 1831, which appeared in
printed form in January, 1832.
[Illustration: FARADAY’S DYNAMO, 1831.
Faraday discovered that electricity could be generated by means of a
permanent magnet. This principle is used in all dynamos.]
Faraday did not develop his invention any further, being satisfied,
as in all his work, in pure research. His was a notable invention but
it remained for others to make it practicable. Hippolyte Pixii, a
Frenchman, made a dynamo in 1832 consisting of a permanent horseshoe
magnet which could be rotated between two wire bobbins mounted on a
soft iron core. The wires from the bobbins were connected to a pair of
brushes touching a commutator mounted on the shaft holding the magnet,
and other brushes carried the current from the commutator so that the
alternating current generated was rectified into direct current.
[Illustration: PIXII’S DYNAMO, 1832.
Pixii made an improvement by rotating a permanent magnet in the
neighborhood of coils of wire mounted on a soft iron core. A commutator
rectified the alternating current generated into direct current. This
dynamo is in the collection of the Smithsonian Institution.]
E. M. Clarke, an Englishman made, in 1834, another dynamo in which the
bobbins rotated alongside of the poles of a permanent horseshoe magnet.
He also made a commutator so that the machine produced direct current.
None of these machines gave more than feeble current at low pressure.
The large primary batteries that had been made were much more powerful,
although expensive to operate. It has been estimated that the cost of
current from the 2000-cell battery to operate the demonstration of the
arc light by Davy, was six dollars a minute. At present retail rates
for electricity sold by lighting companies, six dollars would operate
Davy’s arc light about 500 hours or 30,000 times as long.
DANIELL’S BATTERY
[Illustration: DANIELL’S CELL, 1836.
Daniell invented a battery consisting of zinc, copper and copper
sulphate. Later the porous cup was dispensed with, which was used to
keep the sulphuric acid formed separate from the solution of copper
sulphate, the two liquids then being kept apart by their difference in
specific gravity. It was then called the Gravity Battery and for years
was used in telegraphy.]
It was soon discovered that if the zinc electrode were rubbed with
mercury (amalgamated), the local action would practically cease, and if
the hydrogen bubbles were removed, the operating voltage of the cell
would be increased. John Frederic Daniell, an English chemist, invented
a cell in 1836 to overcome these difficulties. His cell consisted
of a glass jar containing a saturated solution of copper sulphate
(CuSO_{4}). A copper cylinder, open at both ends and perforated with
holes, was put into this solution. On the outside of the copper
cylinder there was a copper ring, located below the surface of the
solution, acting as a shelf to support crystals of copper sulphate.
Inside the cylinder there was a porous earthenware jar containing
dilute sulphuric acid and an amalgamated zinc rod. The two liquids were
therefore kept apart but in contact with each other through the pores
of the jar. The hydrogen gas given off by the action of the sulphuric
acid on the zinc, combined with the dissolved copper sulphate, formed
sulphuric acid and metallic copper. The latter was deposited on the
copper cylinder which acted as the other electrode. Thus the copper
sulphate acted as a depolarizer.
The chemical reactions in this cell are,
In inner porous jar: Zn + H_{2}SO_{4} = ZnSO_{4} + H_{2}
In outer glass jar: H_{2} + CuSO_{4} = H_{2}SO_{4} + Cu
This cell had an open circuit voltage of a little over one volt. Later
the porous cup was dispensed with, the two liquids being kept apart
by the difference of their specific gravities. This was known as the
Gravity cell, and for years was used in telegraphy.
[Illustration: GROVE’S CELL, 1838.
This consisted of zinc, sulphuric acid, nitric acid and platinum. It
made a very powerful battery. The nitric acid is called the depolarizer
as it absorbs the hydrogen gas formed, thus improving the operating
voltage.]
GROVE’S BATTERY
Sir William Robert Grove, an English Judge and scientist, invented a
cell in 1838 consisting of a platinum electrode in strong nitric acid
in a porous earthenware jar. This jar was put in dilute sulphuric acid
in a glass jar in which there was an amalgamated zinc plate for the
other electrode. This had an open circuit voltage of about 1.9 volts.
The porous jar was used to prevent the nitric acid from attacking the
zinc. The nitric acid was used for the purpose of combining with the
hydrogen gas set free by the action of the sulphuric acid on the zinc,
and hence was the depolarizing agent. Hydrogen combining with nitric
acid forms nitrous peroxide and water. Part of the nitrous peroxide is
dissolved in the water, and the rest escapes as fumes which, however,
are very suffocating.
The chemical equations of this cell are as follows:
In outer glass jar: Zn + H_{2}SO_{4} = ZnSO_{4} + H_{2}
In inner porous jar: H_{2} + 2HNO_{3} = N_{2}O_{4} + 2H_{2}O
An interesting thing about Grove’s cell is that it was planned in
accordance with a theory. Grove knew that the electrical energy of
the zinc-sulphuric acid cell came from the chemical affinity of the
two reagents, and if the hydrogen gas set free could be combined with
oxygen (to form water--H_{2}O), such chemical affinity should increase
the strength of the cell. As the hydrogen gas appears at the other
electrode, the oxidizing agent should surround that electrode. Nitric
acid was known at that time as one of the most powerful oxidizing
liquids, but as it attacks copper, he used platinum for the other
electrode. Thus he not only overcame the difficulty of polarization by
the hydrogen gas, but also increased the voltage of the cell by the
added chemical action of the combination of hydrogen and oxygen.
GROVE’S DEMONSTRATION OF INCANDESCENT LIGHTING
In 1840 Grove made an experimental lamp by attaching the ends of a coil
of platinum wire to copper wires, the lower parts of which were well
varnished for insulation. The platinum wire was covered by a glass
tumbler, the open end set in a glass dish partly filled with water.
This prevented draughts of air from cooling the incandescent platinum,
and the small amount of oxygen of the air in the tumbler reduced the
amount of oxidization of the platinum that would otherwise occur. With
current supplied by a large number of cells of his battery, he lighted
the auditorium of the Royal Institution with these lamps during one
of the lectures he gave. This lamp gave only a feeble light as there
was danger of melting the platinum and platinum gives but little light
unless operated close to its melting temperature. It also required a
lot of current to operate it as the air tended to cool the incandescent
platinum. The demonstration was only of scientific interest, the cost
of current being much too great (estimated at several hundred dollars a
kilowatt hour) to make it commercial.
GRENET BATTERY
It was discovered that chromic anhydride gives up oxygen easier than
nitric acid and consequently if used would give a higher voltage than
Grove’s nitric acid battery. It also has the advantage of a lesser
tendency to attack zinc directly if it happens to come in contact with
it. Grenet developed a cell having a liquid consisting of a mixture of
potassium bichromate (K_{2}Cr_{2}O_{7}) and sulphuric acid. A porous
cell was therefore not used to keep the two liquids apart. This had the
advantage of reducing the internal resistance. The chemical reaction
was:
K_{2}Cr_{2}O_{7} (potassium bichromate) + 7H_{2}SO_{4} (sulphuric
acid) + 3Zn (zinc) = 3ZnSO_{4} (zinc sulphate) + K_{2}SO_{4}
(potassium sulphate) + Cr_{2} (SO_{4})_{3} (chromium sulphate)
+ 7H_{2}O (water).
In order to prevent the useless consumption of zinc on open circuit,
the zinc was attached to a sliding rod and could be drawn up into the
neck of the bottle-shaped jar containing the liquid.
[Illustration: GROVE’S INCANDESCENT LAMP, 1840.
Grove made an experimental lamp, using platinum for the burner which
was protected from draughts of air by a glass tumbler.]
DE MOLEYNS’ INCANDESCENT LAMP
Frederick De Moleyns, an Englishman, has the honor of having obtained
the first patent on an incandescent lamp. This was in 1841 and his
lamp was quite novel. It consisted of a spherical glass globe, in the
upper part of which was a tube containing powdered charcoal. This tube
was open at the bottom inside the globe and through it ran a platinum
wire, the end below the tube being coiled. Another platinum wire coiled
at its upper end came up through the lower part of the globe but did
not quite touch the other platinum coil. The powdered charcoal filled
the two coils of platinum wire and bridged the gap between. Current
passing through this charcoal bridge heated it to incandescence. The
air in the globe having been removed as far as was possible with the
hand air pumps then available, the charcoal did not immediately burn
up, the small amount consumed being replaced by the supply in the
tube. The idea was ingenious but the lamp was impractical as the globe
rapidly blackened from the evaporation of the incandescent charcoal.
[Illustration: DE MOLEYNS’ INCANDESCENT LAMP, 1841.
This consisted of two coils of platinum wire containing powdered
charcoal operating in a vacuum. It is only of interest as the first
incandescent lamp on which a patent (British) was granted.]
EARLY DEVELOPMENTS OF THE ARC LAMP
It had been found that most of the light of the arc came from the
tip of the positive electrode, and that the charcoal electrodes were
rapidly consumed, the positive electrode about twice as fast as the
negative. Mechanisms were designed to take care of this, together with
devices to start the arc by allowing the electrodes to touch each other
and then pulling them apart the proper distance. This distance varied
from one-eighth to three-quarters of an inch.
In 1840 Bunsen, the German chemist who invented the bunsen burner,
devised a process for making hard dense carbon pencils which lasted
much longer than the charcoal previously used. The dense carbon from
the inside of the retorts of gas making plants was ground up and mixed
with molasses, moulded into shape and baked at a high temperature.
Bunsen also, in 1843, cheapened Grove’s battery by substituting a hard
carbon plate in place of the platinum electrode.
[Illustration: WRIGHT’S ARC LAMP, 1845.
This lamp is also only of interest as the first arc lamp on which a
patent (British) was granted. Four arcs played between the five carbon
discs.]
Thomas Wright, an Englishman, was the first to patent an arc lamp.
This was in 1845, and the lamp was a hand regulated device consisting
of five carbon disks normally touching each other and rotated by
clockwork. Two of the disks could be drawn outward by thumb screws,
which was to be done after the current was turned on thus establishing
four arcs, one between each pair of disks. The next year, 1846, W. E.
Staite, another Englishman, made an arc lamp having two vertical carbon
pencils. The upper was stationary. The lower was movable and actuated
by clockwork directed by ratchets which in turn were regulated by an
electro-magnet controlled by the current flowing through the arc. Thus
the lower carbon would be moved up or down as required.
Archereau, a Frenchman, made a very simple arc lamp in 1848. The upper
carbon was fixed and the lower one was mounted on a piece of iron
which could be drawn down into a coil of wire. The weight of the lower
electrode was overbalanced by a counterweight, so that when no current
was flowing the two carbons would touch. When current was turned on, it
flowed through the two carbons and through the coil of wire (solenoid)
which then became energized and pulled the lower carbon down, thus
striking the arc. Two of these arc lamps were installed in Paris
and caused considerable excitement. After a few weeks of unreliable
operation, it was found that the cost of current from the batteries was
much too great to continue their use commercially. The dynamo had not
progressed far enough to permit its use.
[Illustration: ARCHEREAU’S ARC LAMP, 1848.
This simple arc was controlled by an electro-magnet, and two lamps were
installed for street lighting in Paris, current being obtained from
batteries.]
JOULE’S LAW
Joule was an Englishman, and in 1842 began investigating the relation
between mechanical energy and heat. He first showed that, by allowing
a weight to drop from a considerable height and turn a paddle wheel in
water, the temperature of the water would increase in relation to the
work done in turning the wheel. It is now known that 778 foot-pounds
(1 lb. falling 778 feet, 10 lbs. falling 77.8 feet or 778 lbs. falling
one foot, etc.) is the mechanical equivalent of energy equal to raising
one pound of water one degree Fahrenheit. The rate of energy (power)
is the energy divided by a unit of time; thus one horsepower is 33,000
foot-pounds per minute. Joule next investigated the relation between
heat and electric current. He made a device consisting of a vessel of
water in which there were a thermometer and an insulated coil of wire
having a considerable resistance. He found that an electric current
heated the water, and making many combinations of the amount and length
of time of current flowing and of the resistance of the wire, he
deduced the law that the energy in an electric circuit is proportional
to the square of the amount of current flowing multiplied by the length
of time and multiplied by the resistance of the wire.
The rate of electrical energy (electric power) is therefore
proportional to the square of current multiplied by the resistance.
The electrical unit of power is now called the WATT, named in honor of
James Watt, the Englishman, who made great improvements to the steam
engine about a century ago. Thus, watts = C^{2}R and substituting the
value of R from Ohm’s law, C = E/R, we get
Watts = Volts × Amperes
The watt is a small unit of electric power, as can be seen from the
fact that 746 watts are equal to one horsepower. The kilowatt, kilo
being the Greek word for thousand, is 1000 watts.
This term is an important one in the electrical industry. For example,
dynamos are rated in kilowatts, expressed as KW; the largest one
made so far is 50,000 KW which is 66,666 horsepower. Edison’s first
commercial dynamo had a capacity of 6 KW although the terms watts
and kilowatts were not in use at that time. The ordinary sizes of
incandescent lamps now used in the home are 25, 40 and 50 watts.
STARR’S INCANDESCENT LAMP
[Illustration: STARR’S INCANDESCENT LAMP, 1845.
This consisted of a short carbon pencil operating in the vacuum above a
column of mercury.]
J. W. Starr, an American, of Cincinnati, Ohio, assisted financially by
Peabody, the philanthropist, went to England where he obtained a patent
in 1845 on the lamps he had invented, although the patent was taken
out under the name of King, his attorney. One is of passing interest
only. It consisted of a strip of platinum, the active length of which
could be adjusted to fit the battery strength used, and was covered
by a glass globe to protect it from draughts of air. The other, a
carbon lamp, was the first real contribution to the art. It consisted
of a rod of carbon operating in the vacuum above a column of mercury
(Torrecellium vacuum) as in a barometer. A heavy platinum wire was
sealed in the upper closed end of a large glass tube, and connected
to the carbon rod by an iron clamp. The lower end of the carbon rod
was fastened to another iron clamp, the two clamps being held in place
and insulated from each other by a porcelain rod. Attached to the
lower clamp was a long copper wire. Just below the lower clamp, the
glass tube was narrowed down and had a length of more than 30 inches.
The tube was then filled with mercury, the bottom of the tube being
put into a vessel partly full of mercury. The mercury ran out of the
enlarged upper part of the tube, coming to rest in the narrow part
of the tube as in a barometer, so that the carbon rod was then in a
vacuum. One lamp terminal was the platinum wire extending through the
top of the tube, and the other was the mercury. Several of these lamps
were put on exhibition in London, but were not a commercial success
as they blackened very rapidly. Starr started his return trip to the
United States the next year, but died on board the ship when he was but
25 years old.
OTHER EARLY INCANDESCENT LAMPS
[Illustration: STAITE’S INCANDESCENT LAMP, 1848.
The burner was of platinum and iridium.]
[Illustration: ROBERTS’ INCANDESCENT LAMP, 1852.
It had a graphite burner operating in vacuum.]
In 1848 W. E. Staite, who two years previously had made an arc lamp,
invented an incandescent lamp. This consisted of a platinum-iridium
burner in the shape of an inverted U, covered by a glass globe. It had
a thumb screw for a switch, the whole device being mounted on a bracket
which was used for the return wire. E. C. Shepard, another Englishman,
obtained a patent two years later on an incandescent lamp consisting of
a weighted hollow charcoal cylinder the end of which pressed against a
charcoal cone. Current passing through this high resistance contact,
heated the charcoal to incandescence. It operated in a glass globe from
which the air could be exhausted. M. J. Roberts obtained an English
patent in 1852 on an incandescent lamp. This had a graphite rod for a
burner, which could be renewed, mounted in a glass globe. The globe was
cemented to a metallic cap fastened to a piece of pipe through which
the air could be exhausted. After being exhausted, the pipe, having a
stop cock, could be screwed on a stand to support the lamp.