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Electricity is a form
of energy. Electricity is the flow of electrons. All matter is made up of
atoms, and an atom has a center, called a nucleus. The nucleus contains
positively charged particles called protons and uncharged particles called
neutrons. The nucleus of an atom is surrounded by negatively charged
particles called electrons. The negative charge of an electron is equal to
the positive charge of a proton, and the number of electrons in an atom is
usually equal to the number of protons. When the balancing force between
protons and electrons is upset by an outside force, an atom may gain or
lose an electron. When electrons are "lost" from an atom, the free
movement of these electrons constitutes an electric current.
Electricity is a basic part of nature and it is one of our most widely
used forms of energy. We get electricity, which is a secondary energy
source, from the conversion of other sources of energy, like coal, natural
gas, oil, nuclear power and other natural sources, which are called
primary sources. Many cities and towns were built alongside waterfalls (a
primary source of mechanical energy) that turned water wheels to perform
work. Before electricity generation began slightly over 100 years ago,
houses were lit with kerosene lamps, food was cooled in iceboxes, and
rooms were warmed by wood-burning or coal-burning stoves. Beginning with
Benjamin Franklin's experiment with a kite one stormy night in
Philadelphia, the principles of electricity gradually became understood.
In the mid-1800s, everyone's life changed with the invention of the
electric light bulb. Prior to 1879, electricity had been used in arc
lights for outdoor lighting. The light bulb's invention used electricity
to bring indoor lighting to our homes.
HOW IS ELECTRICITY GENERATED?
An electric generator is a device for converting mechanical energy into
electrical energy. The process is based on the relationship between
magnetism and electricity. When a wire or any other electrically
conductive material moves across a magnetic field, an electric current
occurs in the wire. The large generators used by the electric utility
industry have a stationary conductor. A magnet attached to the end of a
rotating shaft is positioned inside a stationary conducting ring that is
wrapped with a long, continuous piece of wire. When the magnet rotates, it
induces a small electric current in each section of wire as it passes.
Each section of wire constitutes a small, separate electric conductor. All
the small currents of individual sections add up to one current of
considerable size. This current is what is used for electric power.
HOW IS A TRANSFORMER USED?
To solve the problem of sending electricity over long distances, George
Westinghouse developed a device called a transformer. The transformer
allowed electricity to be efficiently transmitted over long distances.
This made it possible to supply electricity to homes and businesses
located far from the electric generating plant.
Despite its great importance in our daily lives, most of us rarely stop to
think what life would be like without electricity. Yet like air and water,
we tend to take electricity for granted. Everyday, we use electricity to
do many functions for us -- from lighting and heating/cooling our homes,
to being the power source for televisions and computers. Electricity is a
controllable and convenient form of energy used in the applications of
heat, light and power.
Today, the United States (U.S.) electric power industry is organized to
ensure that an adequate supply of electricity is available to meet all
demand requirements at any given instant.
HOW ARE TURBINES USED TO GENERATE ELECTRICITY?
An electric utility power station uses either a turbine, engine, water
wheel, or other similar machine to drive an electric generator or a device
that converts mechanical or chemical energy to electricity. Steam
turbines, internal-combustion engines, gas combustion turbines, water
turbines, and wind turbines are the most common methods to generate
electricity.
Most of the electricity in the United States is produced in steam
turbines. A turbine converts the kinetic energy of a moving fluid (liquid
or gas) to mechanical energy. Steam turbines have a series of blades
mounted on a shaft against which steam is forced, thus rotating the shaft
connected to the generator. In a fossil-fueled steam turbine, the fuel is
burned in a furnace to heat water in a boiler to produce steam.
Coal, petroleum (oil), and natural gas are burned in large furnaces to
heat water to make steam that in turn pushes on the blades of a turbine.
Did you know that coal is the largest single primary source of energy used
to generate electricity in the United States? In 1998, more than half
(52%) of the county's 3.62 trillion kilowatt-hours of electricity used coal
as its source of energy.
Natural gas, in addition to being burned to heat water for steam, can also
be burned to produce hot combustion gases that pass directly through a
turbine, spinning the blades of the turbine to generate electricity. Gas
turbines are commonly used when electricity utility usage is in high
demand. In 1998, 15% of the nation's electricity was fueled by natural
gas.
Petroleum can also be used to make steam to turn a turbine. Residual fuel
oil, a product refined from crude oil, is often the petroleum product used
in electric plants that use petroleum to make steam. Petroleum was used to
generate less than three percent (3%) of all electricity generated in U.S.
electricity plants in 1998.
The electricity produced by a generator travels along cables to a
transformer, which changes electricity from low voltage to high voltage.
Electricity can be moved long distances more efficiently using high
voltage. Transmission lines are used to carry the electricity to a
substation. Substations have transformers that change the high voltage
electricity into lower voltage electricity. From the substation,
distribution lines carry the electricity to homes, offices and factories,
which require low voltage electricity.
HOW IS ELECTRICITY MEASURED?
Electricity is measured in units of power called watts. It was named to
honor James Watt, the inventor of the steam engine. One watt is a very
small amount of power. It would require nearly 750 watts to equal one
horsepower. A kilowatt represents 1,000 watts. A kilowatt-hour (kWh) is
equal to the energy of 1,000 watts working for one hour. The amount of
electricity a power plant generates or a customer uses over a period of
time is measured in kilowatt-hours (kWh). Kilowatt-hours are determined by
multiplying the number of kW's required by the number of hours of use. For
example, if you use a 40-watt light bulb 5 hours a day, you have used 200
watts of power, or .2 kilowatt-hours of electrical energy.
This article is from about.com |
