In the sciences, once a hypothesis is proven and accepted, it becomes
one of the building blocks of that area of study, permitting additional
investigation and development. Naturally, the more pieces of a puzzle
available, the more obvious the avenue toward a possible solution. In
fact, history demonstrates that a single development may provide the
key that will result in a mushroom effect that brings the science to a
new plateau of understanding and impact.
As you will see from the discussion of the late 1700s and the early 1800s,
inventions, discoveries, and theories came fast and furiously. Each new
concept has broadened the possible areas of application until it becomes
almost impossible to trace developments without picking a particular
area of interest and following it through.
There is a tendency when reading about the great scientists, inventors,
and innovators to believe that their contribution was a totally individual
effort. In many instances, this was not the case. In fact, many of the great
contributors were friends or associates who provided support and
encouragement in their efforts to investigate various theories. At the very
least, they were aware of one another's efforts to the degree possible in
the days when a letter was often the best form of communication. In particular, note the closeness of the dates during periods of rapid development. One contributor seemed to spur on the efforts of the others or possibly provided the key needed to continue with the area of interest.
In the early stages, the contributors were not
electrical,
electronic, or
computer engineers as we know them today. In most cases, they were
physicists,
chemists,
mathematicians, or even
philosophers. In addition,
they were not from one or two communities of the Old World. The home
country of many of the major contributors introduced in the paragraphs
to follow is provided to show that almost every established community
had some impact on the development of the fundamental laws of
electrical circuits.
As you proceed through the remaining chapters of the text, you will
find that a number of the units of measurement bear the name of major
contributors in those areas,
volt after
Count Alessandro Volta,
ampere
after
Andre Ampere,
ohm after
Georg Ohm, and so forth fitting recognition for their important contributions to the birth of a major field of study.
In essence, the current state of the art is a result of efforts that began in earnest some 250 years ago, with progress in the last 100 years
almost exponential.
The Beginning
The phenomenon of
static electricity has been toyed with since antiquity. The Greeks called the
fossil resin substance so often used to
demonstrate the effects of static electricity
elektron, but no extensive
study was made of the subject until
William Gilbert researched the
event in 1600. In the years to follow, there was a continuing investigation of electrostatic charge by many individuals such as
Otto von Guericke, who developed the first machine to generate large amounts of
charge, and
Stephen Gray, who was able to transmit
electrical charge
over long distances on silk threads.
Charles DuFay demonstrated that
charges either attract or repel each other, leading him to believe that
there were two types of charge - a theory we subscribe to today with
our defined
positive and
negative charges.
There are many who believe that the true beginnings of the electrical
era lie with the efforts of
Pieter van Musschenbroek and
Benjamin
Franklin. In 1745, van Musschenbroek introduced the
Leyden jar for
the storage of
electrical charge (
the first capacitor) and demonstrated
electrical shock (and therefore the power of this new form of
energy).
Franklin used the Leyden jar some seven years later to establish that
lightning is simply an
electrical discharge, and he expanded on a number of other important theories including the definition of the two types
of charge as
positive and
negative. From this point on, new discoveries
and theories seemed to occur at an increasing rate as the number of
individuals performing research in the area grew.
In 1784,
Charles Coulomb demonstrated in Paris that the force
between charges is inversely related to the square of the distance
between the charges. In 1791,
Luigi Galvani, professor of anatomy at
the University of Bologna, Italy, performed experiments on the effects
of electricity on animal nerves and muscles. The
first voltaic cell, with
its ability to produce electricity through the chemical action of a metal
dissolving in an acid, was developed by another Italian,
Alessandro
Volta, in 1799.
The fever pitch continued into the early 1800s with
Hans Christian
Oersted, a Swedish professor of physics, announcing in 1820 a relationship between
magnetism and
electricity that serves as the foundation for
the theory of electromagnetism as we know it today. In the same year, a
French physicist,
Andre, demonstrated that there are magnetic
effects around every
current-carrying conductor and that current-carrying conductors can attract and repel each other just like magnets. In the
period 1826 to 1827, a German physicist,
Georg Ohm, introduced an
important relationship between
potential,
current, and
resistance which
we now refer to as Ohm's law. In 1831, an English physicist,
Michael
Faraday, demonstrated his theory of
electromagnetic induction, whereby
a changing current in one coil can induce a changing current in another
coil, even though the two coils are not directly connected. Professor
Faraday also did extensive work on a storage device he called the condenser, which we refer to today as a
capacitor.
He introduced the idea of adding a dielectric between the plates of a capacitor to increase the storage capacity.
James Clerk Maxwell, a Scottish professor of
natural philosophy, performed extensive mathematical analyses to
develop what are currently called
Maxwell's equations, which support
the efforts of Faraday linking electric and magnetic effects. Maxwell also
developed the
electromagnetic theory of light in 1862, which, among
other things, revealed that electromagnetic waves travel through air
at the velocity of light ($186,000$ miles per second or $3 \times 10^8$ meters
per second). In 1888, a German physicist,
Heinrich Rudolph Hertz,
through experimentation with lower-frequency electromagnetic waves
(microwaves), substantiated Maxwell's predictions and equations. In the
mid 1800s, Professor
Gustav Robert Kirchhoff introduced a series of
laws of voltages and currents that find application at every level and area
of this field. In 1895, another German physicist,
Wilhelm Rontgen, discovered electromagnetic waves of high
frequency,
commonly called
X rays today.
By the end of the 1800s, a significant number of the fundamental
equations, laws, and relationships had been established, and various
fields of study, including electronics, power generation, and calculating
equipment, started to develop in earnest.
The Age of Electronics
Radio
The true beginning of the electronics era is open to debate and
is sometimes attributed to efforts by early scientists in applying potentials across evacuated glass envelopes. However, many trace the beginning to
Thomas Edison, who added a metallic electrode to the vacuum
of the tube and discovered that a current was established between the
metal electrode and the filament when a positive voltage was applied to
the metal electrode. The phenomenon, demonstrated in 1883, was
referred to as the Edison effect. In the period to follow, the transmission of radio waves and the development of the radio received widespread attention. In 1887,
Heinrich Hertz, in his efforts to verify
Maxwell's equations, transmitted radio waves for the first time in his
laboratory. In 1896, an Italian scientist,
Guglielmo Marconi (often
called the father of the radio), demonstrated that telegraph signals could
be sent through the air over long distances (2.5 kilometers) using a
grounded antenna. In the same year,
Aleksandr Popov sent what might
have been the
first radio message some 300 yards. The message was the
name "Heinrich Hertz" in respect for Hertz's earlier contributions. In
1901, Marconi established radio communication across the Atlantic.
In 1904,
John Ambrose Fleming expanded on the efforts of Edison
to develop the
first diode, commonly called
Fleming's valve actually
the first of the electronic devices. The device had a profound impact on
the design of detectors in the receiving section of radios. In 1906,
Lee
De Forest added a third element to the vacuum structure and created the
first amplifier, the
triode. Shortly thereafter, in 1912,
Edwin Armstrong
built the first regenerative circuit to improve receiver capabilities and
then used the same contribution to develop the first nonmechanical
oscillator.
By 1915 radio signals were being transmitted across the
United States, and in 1918 Armstrong applied for a patent for the super heterodyne circuit employed in virtually every television and radio to
permit amplification at one frequency rather than at the full range of incoming signals. The major components of the modern-day radio were
now in place, and sales in radios grew from a few million dollars in the
early 1920s to over $1 billion by the 1930s. The 1930s were truly the
golden years of radio, with a wide range of productions for the listening audience.
Television
The 1930s were also the true beginnings of the television
era, although development on the picture tube began in earlier years
with
Paul Nipkow and his electrical telescope in 1884 and
John Baird
and his long list of successes, including the transmission of television
pictures over telephone lines in 1927 and over radio waves in 1928, and
simultaneous transmission of pictures and sound in 1930. In 1932, NBC
installed the first commercial television antenna on top of the Empire
State Building in New York City, and RCA began regular broadcasting
in 1939. The war slowed development and sales, but in the mid 1940s
the number of sets grew from a few thousand to a few million. Color
television became popular in the early 1960s.
Computers
The earliest computer system can be traced back to
Blaise Pascal in 1642 with his mechanical machine for adding and subtracting numbers. In 1673
Gottfried Wilhelm von Leibniz used the
Leibniz wheel to add multiplication and division to the range of operations, and in 1823
Charles Babbage developed the difference engine to
add the mathematical operations of sine, cosine, logs, and several others. In the years to follow, improvements were made, but the system
remained primarily mechanical until the 1930s when electromechanical
systems using components such as relays were introduced. It was not
until the 1940s that totally electronic systems became the new wave. It
is interesting to note that, even though
IBM was formed in 1924, it did
not enter the computer industry until 1937. An entirely electronic system known as
ENIAC was dedicated at the University of Pennsylvania
in 1946. It contained $18,000$ tubes and weighed $30$ tons but was several
times faster than most electromechanical systems. Although other vacuum tube systems were built, it was not until the birth of the
solid-state era that computer systems experienced a major change in size, speed,
and capability.
The Solid-State Era
In 1947, physicists
William Shockley,
John Bardeen, and
Walter H. Brattain of Bell Telephone Laboratories demonstrated the
point-contact
transistor, an amplifier constructed entirely of solid-state
materials with no requirement for a vacuum, glass envelope, or heater
voltage for the filament. Although reluctant at first due to the vast
amount of material available on the design, analysis, and synthesis of
tube networks, the industry eventually accepted this new technology as
the wave of the future. In 1958 the first
integrated circuit (IC) was
developed at Texas Instruments, and in 1961 the first commercial integrated circuit was manufactured by the Fairchild Corporation.
It is impossible to review properly the entire history of the electrical/electronics field in a few pages. The effort here, both through the
discussion and the time graphs was to reveal the amazing
progress of this field in the last 50 years. The growth appears to be truly
exponential since the early 1900s, raising the interesting question,
Where do we go from here? The time chart suggests that the next few
decades will probably contain many important innovative contributions
that may cause an even faster growth curve than we are now experiencing.
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