ENGINEERING UTILITIES 1
CHAPTER 17-20 ELECTRICAL
Electricity is a form of energy tied to the
existence of electrical charge and, as a result, is
related to magnetism. It plays a fundamental
role in all the technologies we use today.
Everyday work and play activities through
manufacturing and scientific research use
electricity as a source of energy. In this chapter,
the theory of electricity, fundamental units, and
costs are introduced. Devices, equipment, and
materials used to distribute electricity from the
power utility to points of use in the building and
building electrical system design methods are
discussed in Chapters 18 and 19.
The History of Electricity
The study and development of electricity
occurred over many centuries. It has its roots
about 600 B.C.E. when a Greek mathematician
named Thales documented what eventually
became known as static electricity. He recorded
that after rubbing amber, a yellowish,
translucent mineral, with a piece of wool or fur
other light objects such as straw or feathers were
attracted to the amber. For centuries this
distinctive property was thought to be unique to
amber. There was little development in the
understanding of electricity until about 1600
when English scientist William Gilbert described
the electrification of many substances. He
coined the term electricity, which is derived from
the Latin term electricus, meaning to “produce
from amber by friction.” It has its roots in the
Greek term elektor, which means, “beaming
sun.”
Gradual
improvements
in
the
understanding of electricity have led to the
invention of motors, generators, telephones,
radio and television, and computers. In 1660, a
German experimenter named Otto von Guericke
built the first electric generating machine. It was
constructed of a ball of sulfur, rotated by a crank
with one hand and rubbed with the other. Other
experimenters
recognized
that
other
substances, such as copper, silver, and gold, did
not attract anything. An Englishman, Stephen
Gray, distinguished between materials that were
conductors and nonconductors in 1729. About
1746, Ewald Georg von Kleist, a German
inventor, and Dutch physicist Pieter van
Musschenbroek of the University of Leyden,
working independently, invented an electrical
storage device called a Leyden jar, a glass jar
coated inside and outside with tin foil. Static
electricity could be discharged by simultaneously
touching the inner and outer foil layers. It
demonstrated that electricity could be stored for
future use. In 1747, American inventor and
statesman, Benjamin Franklin, suggested the
existence of an electrical fluid and surmised that
an electric charge was made up of two types of
electric forces, an attractive force and a
repulsive force. To identify these two forces, he
gave the names positive and negative, which are
still in use today. Franklin conducted his famous
kite experiment in 1752. He flew a kite with a
stiff wire pointing up ward as a thunderstorm
was about to break. He attached a metal key to
the other end of the hemp string, and let it hang
close to a Leyden jar. Rain moistened the string,
which could then con duct electricity. Sparks
jumped from the key to the jar. Al though there
was no lightning, there was enough electricity in
the air for Franklin to prove that electricity and
lightning are the same thing. In 1786, an Italian
anatomy professor, Luigi Galvani, ob served that
a discharge of static electricity made a dead
frog’s leg twitch. Ensuing experimentation
produced what was a sim ple electron cell using
the fluids of the leg as an electrolyte and the
muscle as a circuit and indicator. Expanding on
Galvani’s findings, Alessandro Volta, another
Italian, built the voltaic pile, an early type of
electric cell or battery. In 1820, H. C. Oersted, a
Danish physicist, discovered that a magnetic
field surrounds a current-carrying wire, by
observing that electrical currents affected the
needle on a com pass. Within two years Andre
Marie Ampere, a French mathematician,
observed that a coil of wires acts like a magnet
when electrical current is passed thorough it.
Shortly thereafter, D. F. Arago invented the
electromagnet and Joseph Henry, an American,
demonstrated an electromagnetic device that
was capable of lifting over a thousand pounds.
Also as the result of the newly discovered
electromagnet, Michael Faraday, an English
man, developed a crude electric motor in 1831,
but a practical motor was not developed until
1870. Both Faraday and Joseph Henry, working
independently, invented the electric generator
with which to power the motor. In 1831,
American Samuel Morse conceived the idea of
sending coded messages over wires using the
electromagnetic telegraph and a code of
electrical impulses identified as dots and dashes
that eventually became known as “Morse Code.”
The first message sent by the electric telegraph
was “What hath God wrought,” from the
Supreme Court Room in the U.S. Capitol to the
railway depot at Baltimore on May 24, 1844.
Morse’s electric telegraph is recognized as the
first practical use of electricity and the first
system of electrical communication. 573 574
CHAPTER 17 Charles de Coulomb was the first
person to measure the amount of electricity and
magnetism generated in a circuit. G. S. Ohm, a
German college teacher, formulated a law
showing the relationship between volts, amps,
and resistance. Henry and Ohm demonstrated
that in a long electric line it was better to have
relatively high voltage and low current.
Additionally, J. P. Joule, G. R. Kirchhoff, and J. C.
Maxwell
also
developed
mathematical
relationships and rules concerning electrical
circuiting. In the late 1800s, electric lighting was
viewed as an ideal use of electrical energy.
Although arc lights were invented and put to
practical use for lighting streets by 1860, it was
not until 1879 that a practical incandescent lamp
was developed independently by Thomas Edison
in America and Joseph Swan in England. Edison
was the first to patent the commercially feasible
incandescent lamp so he is recognized as the
inventor. The development of electric lighting is
covered in Chapter 20. In 1882, the Edison
Electric Light Company, later known as General
Electric, successfully demonstrated the use of
artificial lighting by powering incandescent
streetlights and lamps in London and New York
City. By the end of the 1880s, small electrical
stations based on Edison’s designs were in use a
number of U.S. cities. However, each power
station was able to power only a few city blocks.
Edison’s designs still serve as the basis of how we
to distribute electricity from power stations with
the exception that Edison’s systems were direct
current systems. Direct current systems had the
problematic character istic that current could
not be economically transmitted over long
distances. American Nikola Tesla of Croatian
decent, one of Edi son’s former employees and a
rival of Edison at the end of the 19th century, is
the inventor of 3-phase power distribution, the
alternating
current
motor,
wireless
transmission. He began experimenting on
generators in 1883, and discovered the rotating
magnetic field. This phenomenon serves as the
basic principle of the alternating current
generator. Tesla then developed plans for an
alternating current induction motor, which
become the first step towards the successful
utilization of alternating current. In 1885, George
Westinghouse, head of the Westing house
Electric Company, bought the patent rights to
Tesla’s alternating current system. In America, in
1886 the first alternating current power station
was placed in operation, but as no alternating
current motor was available, the output of this
station was limited to lighting. In 1888, the
alternating current motor was introduced and
ultimately became the most commonly used
electric motor in buildings (e.g., for fans, air
conditioners, and refrigerators). L. Caulard and J.
D. Gibbs announced the first transformer in
1883. This allowed alternating current power to
be generated at low voltage, then stepped up to
high voltage for efficient transmission, and then
stepped down to an even lower voltage for
safety reasons. Large-scale electric power
distribution began on August 26, 1895, when
water flowing over Niagara Falls was diverted
through a pair of high-speed turbines that were
coupled to two 5000-horsepower generators
that powered nearby manufacturing plants. The
following year a portion was transmitted 20
miles to the city of Buffalo, where it was used for
powering lighting and streetcars. This project
involved generators produced by Westinghouse
and later by General Electric. The Niagara project
clearly demonstrated that large-scale generation
and transmission of electricity was conceptually
sound, technically feasible, and economically
practical. Gradually, electrical power became
commercialized in urban areas of the U.S. Gas
lighting that had been used in streetlights was re
placed by electric lights and overhead wires
eventually connected homes to a large-scale
power plant operated by privately owned
electric companies. By about 1930 most of the
occupants of large cities in the United States had
electricity, yet only 10% of the Americans who
lived in rural areas had electricity. At this time,
private electric utilities determined that it was
too expensive to run long transmission lines to
spaced farms. The Roosevelt administration
believed that if private enterprise could not
supply electric power to the people, then it was
the duty of the government to do so. In 1935, the
Rural Electric Administration (REA) was created
to bring electricity to these rural areas. The REA
helped to establish hundreds of electric
cooperatives that served millions of rural
households. Reliance on electricity has grown
significantly over the past decade in all countries.
For example, in 2002, the U.S. Department of
Energy reported that total U.S. net generation of
electricity was 3811 billion kWh, with 50%
produced by coal fired plants, 20% from nuclear
plants, 18% from gas plants, 7% from
hydroelectric plants, 2% from petroleum-fired
plants, and 2% from renewable power sources
(e.g., wind, solar electric, and so on). In less than
a century, the developed world has become
extremely dependent on electricity and
problems have occurred because of this
dependence. In 1965, 1977, and 2003, power
failures blacked out much of the northeastern
United States and Canada. In 1994 California
enacted legislation intended to deregulate the
electric power business in the state and establish
a competitive market. It was heralded as a model
for developed countries to follow. But, by
January 2001, flaws in the California approach
had become evident with the state’s utilities
driven to the brink of bankruptcy and
Californians suffering electricity shortages and
blackouts. The effects of shortages and
blackouts experienced by the general public
have under scored the significance of electricity
in everyday life.