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Electricity
Electricity is a form of energy characterized by the presence and motion of elementary charged
particles generated by friction, induction, or chemical change. Electricity is a secondary energy
source which means that we get it from the conversion of other sources of energy, like coal,
natural gas, oil, nuclear power and other natural sources, which are called primary sources. The
energy sources we use to make electricity can be renewable or non-renewable, but electricity
itself is neither renewable or non-renewable.
What is Electricity?
Electricity is the flow of electrical power or charge. It is a secondary energy source which means
that we get it from the conversion of other sources of energy, like coal, natural gas, oil, nuclear
power and other natural sources, which are called primary sources. The energy sources we use
to make electricity can be renewable or non-renewable, but electricity itself is neither renewable
or non-renewable.
Electricity is a basic part of nature and it is one of our most widely used forms of energy. 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 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.
Thomas Edison helped change everyone's life -- he perfected his invention -- the electric light bulb.
Prior to 1879, direct current (DC) electricity had been used in arc lights for outdoor lighting. In the
late-1800s, Nikola Tesla pioneered the generation, transmission, and use of alternating current
(AC) electricity, which can be transmitted over much greater distances than direct current.
Tesla's inventions used electricity to bring indoor lighting to our homes and to power industrial
machines.
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 jobs for us -- from lighting and heating/cooling our homes, to powering
our televisions and computers. Electricity is a controllable and convenient form of energy used in
the applications of heat, light and power.
The Science of Electricity
In order to understand how electric charge moves from one atom to another, we need to know
something about atoms. Everything in the universe is made of atoms—every star, every tree,
every animal. The human body is made of atoms. Air and water are, too. Atoms are the building
blocks of the universe. Atoms are so small that millions of them would fit on the head of a pin.
Atoms are made of even smaller particles. The center of an atom is called the nucleus. It is made
of particles called protons and neutrons. The protons and neutrons are very small, but electrons
are much, much smaller. Electrons spin around the nucleus in shells a great distance from the
nucleus. If the nucleus were the size of a tennis ball, the atom would be the size of the Empire
State Building. Atoms are mostly empty space.
If you could see an atom, it would look a little like a tiny center of balls surrounded by giant
invisible bubbles (or shells). The electrons would be on the surface of the bubbles, constantly
spinning and moving to stay as far away from each other as possible. Electrons are held in their
shells by an electrical force.
The protons and electrons of an atom are attracted to each other. They both carry an electrical
charge. An electrical charge is a force within the particle. Protons have a positive charge (+) and
electrons have a negative charge (-). The positive charge of the protons is equal to the negative
charge of the electrons. Opposite charges attract each other. When an atom is in balance, it has
an equal number of protons and electrons. The neutrons carry no charge and their number can
vary.
The number of protons in an atom determines the kind of atom, or element, it is. An element is a
substance in which all of the atoms are identical (the Periodic Table shows all the known
elements). Every atom of hydrogen, for example, has one proton and one electron, with no
neutrons. Every atom of carbon has six protons, six electrons, and six neutrons. The number of
protons determines which element it is.
Electrons usually remain a constant distance from the nucleus in precise shells. The shell closest
to the nucleus can hold two electrons. The next shell can hold up to eight. The outer shells cans
hold even more. Some atoms with many protons can have as many as seven shells with electrons
in them.
The electrons in the shells closest to the nucleus have a strong force of attraction to the protons.
Sometimes, the electrons in the outermost shells do not. These electrons can be pushed out of
their orbits. Applying a force can make them move from one atom to another. These moving
electrons are electricity.
What is static electricity?
Electricity has been moving in the world forever. Lightning is a form of electricity. It is electrons
moving from one cloud to another or jumping from a cloud to the ground. Have you ever felt a
shock when you touched an object after walking across a carpet? A stream of electrons jumped
to you from that object. This is called static electricity.
Have you ever made your hair stand straight up by rubbing a balloon on it? If so, you rubbed some
electrons off the balloon. The electrons moved into your hair from the balloon. They tried to get far
away from each other by moving to the ends of your hair.
They pushed against each other and made your hair move�they repelled each other. Just as
opposite charges attract each other, like charges repel each other.
What is the relationship between magnets and electricity?
The spinning of the electrons around the nucleus of an atom creates a tiny magnetic field. Most
objects are not magnetic because the atoms are arranged so that the electrons spin in different,
random directions, and cancel out each other.
Magnets are different; the molecules in magnets are arranged so that the electrons spin in the
same direction. This arrangement of atoms creates two poles in a magnet, a North-seeking pole
and a South-seeking pole.
A magnet is labeled with North (N) and South (S) poles. The magnetic force in a magnet flows from
the North pole to the South pole. This creates a magnetic field around a magnet.
Have you ever held two magnets close to each other? They don�t act like most objects. If you try
to push the South poles together, they repel each other. Two North poles also repel each other.
Turn one magnet around and the North (N) and the South (S) poles are attracted to each other. The
magnets come together with a strong force. Just like protons and electrons, opposites attract.
These special properties of magnets can be used to make electricity. Moving magnetic fields can
pull and push electrons. Some metals, like copper have electrons that are loosely held. They can
be pushed from their shells by moving magnets. Magnets and wire are used together in electric
generators.
How Does Battery Procedure Electricity?
A battery produces electricity using two different metals in a chemical solution. A chemical
reaction between the metals and the chemicals frees more electrons in one metal than in the
other. One end of the battery is attached to one of the metals; the other end is attached to the
other metal. The end that frees more electrons develops a positive charge and the other end
develops a negative charge. If a wire is attached from one end of the battery to the other,
electrons flow through the wire to balance the electrical charge. A load is a device that does work
or performs a job. If a load��such as a lightbulb��is placed along the wire, the electricity can do
work as it flows through the wire. In the picture above, electrons flow from the negative end of the
battery through the wire to the lightbulb. The electricity flows through the wire in the lightbulb and
back to the battery.
How Does Electricity Travel?
Electricity travels in closed loops, or circuits (from the word circle). It must have a complete path
before the electrons can move. If a circuit is open, the electrons cannot flow. When we flip on a
light switch, we close a circuit. The electricity flows from the electric wire through the light and
back into the wire. When we flip the switch off, we open the circuit. No electricity flows to the light.
When we turn a light switch on, electricity flows through a tiny wire in the bulb. The wire gets very
hot. It makes the gas in the bulb glow. When the bulb burns out, the tiny wire has broken. The path
through the bulb is gone. When we turn on the TV, electricity flows through wires inside the set,
producing pictures and sound. Sometimes electricity runs motors�in washers or mixers.
Electricity does a lot of work for us. We use it many times each day.
How is electricity generated?
A generator is a device that converts mechanical energy into electrical energy. The process is
based on the relationship between magnetism and electricity. In 1831, Faraday discovered that
when a magnet is moved inside a coil of wire, electrical current flows in the wire.
A typical generator at a power plant uses an electromagnet—a magnet produced by electricity—
not a traditional magnet. The generator has a series of insulated coils of wire that form a
stationary cylinder. This cylinder surrounds a rotary electromagnetic shaft. When the
electromagnetic shaft rotates, it induces a small electric current in each section of the wire coil.
Each section of the wire becomes a small, separate electric conductor. The small currents of
individual sections are added together to form one large current. This current is the electric
power that is transmitted from the power company to the consumer.
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
generate electricity. Steam turbines, internal-combustion engines, gas combustion turbines,
water turbines, and wind turbines are the most common methods to generate electricity. Most
power plants are about 35 percent efficient. That means that for every 100 units of energy that go
into a plant, only 35 units are converted to usable electrical energy.
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 most electricity generated in the United State comes from burning coal? In
2006, nearly half (49%) of the country's 4.1 trillion kilowatthours 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 2006, 20% 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 about two percent (2%) of all electricity generated in U.S.
electricity plants in 2006.
Nuclear power is a method in which steam is produced by heating water through a process called
nuclear fission. In a nuclear power plant, a reactor contains a core of nuclear fuel, primarily
enriched uranium. When atoms of uranium fuel are hit by neutrons they fission (split), releasing
heat and more neutrons. Under controlled conditions, these other neutrons can strike more
uranium atoms, splitting more atoms, and so on. Thereby, continuous fission can take place,
forming a chain reaction releasing heat. The heat is used to turn water into steam, that, in turn,
spins a turbine that generates electricity. Nuclear power was used to generate 19% of all the
country's electricity in 2006.
Hydropower, the source for almost 7% of U.S. electricity generation in 2006, is a process in which
flowing water is used to spin a turbine connected to a generator. There are two basic types of
hydroelectric systems that produce electricity. In the first system, flowing water accumulates in
reservoirs created by the use of dams. The water falls through a pipe called a penstock and
applies pressure against the turbine blades to drive the generator to produce electricity. In the
second system, called run-of-river, the force of the river current (rather than falling water) applies
pressure to the turbine blades to produce electricity.
Geothermal power comes from heat energy buried beneath the surface of the earth. In some
areas of the country, enough heat rises close to the surface of the earth to heat underground
water into steam, which can be tapped for use at steam-turbine plants. This energy source
generated less than 1% of the electricity in the country in 2006.
Solar power is derived from the energy of the sun. However, the sun's energy is not available full-
time and it is widely scattered. The processes used to produce electricity using the sun's energy
have historically been more expensive than using conventional fossil fuels. Photovoltaic
conversion generates electric power directly from the light of the sun in a photovoltaic (solar) cell.
Solar-thermal electric generators use the radiant energy from the sun to produce steam to drive
turbines. In 2006, less than 1% of the nation's electricity was based on solar power.
Wind power is derived from the conversion of the energy contained in wind into electricity. Wind
power, less than 1% of the nation's electricity in 2006, is a rapidly growing source of electricity. A
wind turbine is similar to a typical wind mill.
Biomass includes wood, municipal solid waste (garbage), and agricultural waste, such as corn
cobs and wheat straw. These are some other energy sources for producing electricity. These
sources replace fossil fuels in the boiler. The combustion of wood and waste creates steam that
is typically used in conventional steam-electric plants. Biomass accounts for about 1% of the
electricity generated in the United States.
What is a transformer?
To solve the problem of sending electricity over long distances, William Stanley 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.
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 do you measure electricity?
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 kilowatthour (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 kilowatthours (kWh).
Kilowatthours 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 watthours, or
0.2 kilowatthours, of electrical energy. See our Energy Calculator section to learn more about
converting units.
Electricity is a form of energy characterized by the presence and motion of elementary charged
particles generated by friction, induction, or chemical change. Electricity is a secondary energy
source which means that we get it from the conversion of other sources of energy, like coal,
natural gas, oil, nuclear power and other natural sources, which are called primary sources. The
energy sources we use to make electricity can be renewable or non-renewable, but electricity
itself is neither renewable or non-renewable.
What is Electricity?
Electricity is the flow of electrical power or charge. It is a secondary energy source which means
that we get it from the conversion of other sources of energy, like coal, natural gas, oil, nuclear
power and other natural sources, which are called primary sources. The energy sources we use
to make electricity can be renewable or non-renewable, but electricity itself is neither renewable
or non-renewable.
Electricity is a basic part of nature and it is one of our most widely used forms of energy. 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 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.
Thomas Edison helped change everyone's life -- he perfected his invention -- the electric light bulb.
Prior to 1879, direct current (DC) electricity had been used in arc lights for outdoor lighting. In the
late-1800s, Nikola Tesla pioneered the generation, transmission, and use of alternating current
(AC) electricity, which can be transmitted over much greater distances than direct current.
Tesla's inventions used electricity to bring indoor lighting to our homes and to power industrial
machines.
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 jobs for us -- from lighting and heating/cooling our homes, to powering
our televisions and computers. Electricity is a controllable and convenient form of energy used in
the applications of heat, light and power.
The Science of Electricity
In order to understand how electric charge moves from one atom to another, we need to know
something about atoms. Everything in the universe is made of atoms—every star, every tree,
every animal. The human body is made of atoms. Air and water are, too. Atoms are the building
blocks of the universe. Atoms are so small that millions of them would fit on the head of a pin.
Atoms are made of even smaller particles. The center of an atom is called the nucleus. It is made
of particles called protons and neutrons. The protons and neutrons are very small, but electrons
are much, much smaller. Electrons spin around the nucleus in shells a great distance from the
nucleus. If the nucleus were the size of a tennis ball, the atom would be the size of the Empire
State Building. Atoms are mostly empty space.
If you could see an atom, it would look a little like a tiny center of balls surrounded by giant
invisible bubbles (or shells). The electrons would be on the surface of the bubbles, constantly
spinning and moving to stay as far away from each other as possible. Electrons are held in their
shells by an electrical force.
The protons and electrons of an atom are attracted to each other. They both carry an electrical
charge. An electrical charge is a force within the particle. Protons have a positive charge (+) and
electrons have a negative charge (-). The positive charge of the protons is equal to the negative
charge of the electrons. Opposite charges attract each other. When an atom is in balance, it has
an equal number of protons and electrons. The neutrons carry no charge and their number can
vary.
The number of protons in an atom determines the kind of atom, or element, it is. An element is a
substance in which all of the atoms are identical (the Periodic Table shows all the known
elements). Every atom of hydrogen, for example, has one proton and one electron, with no
neutrons. Every atom of carbon has six protons, six electrons, and six neutrons. The number of
protons determines which element it is.
Electrons usually remain a constant distance from the nucleus in precise shells. The shell closest
to the nucleus can hold two electrons. The next shell can hold up to eight. The outer shells cans
hold even more. Some atoms with many protons can have as many as seven shells with electrons
in them.
The electrons in the shells closest to the nucleus have a strong force of attraction to the protons.
Sometimes, the electrons in the outermost shells do not. These electrons can be pushed out of
their orbits. Applying a force can make them move from one atom to another. These moving
electrons are electricity.
What is static electricity?
Electricity has been moving in the world forever. Lightning is a form of electricity. It is electrons
moving from one cloud to another or jumping from a cloud to the ground. Have you ever felt a
shock when you touched an object after walking across a carpet? A stream of electrons jumped
to you from that object. This is called static electricity.
Have you ever made your hair stand straight up by rubbing a balloon on it? If so, you rubbed some
electrons off the balloon. The electrons moved into your hair from the balloon. They tried to get far
away from each other by moving to the ends of your hair.
They pushed against each other and made your hair move�they repelled each other. Just as
opposite charges attract each other, like charges repel each other.
What is the relationship between magnets and electricity?
The spinning of the electrons around the nucleus of an atom creates a tiny magnetic field. Most
objects are not magnetic because the atoms are arranged so that the electrons spin in different,
random directions, and cancel out each other.
Magnets are different; the molecules in magnets are arranged so that the electrons spin in the
same direction. This arrangement of atoms creates two poles in a magnet, a North-seeking pole
and a South-seeking pole.
A magnet is labeled with North (N) and South (S) poles. The magnetic force in a magnet flows from
the North pole to the South pole. This creates a magnetic field around a magnet.
Have you ever held two magnets close to each other? They don�t act like most objects. If you try
to push the South poles together, they repel each other. Two North poles also repel each other.
Turn one magnet around and the North (N) and the South (S) poles are attracted to each other. The
magnets come together with a strong force. Just like protons and electrons, opposites attract.
These special properties of magnets can be used to make electricity. Moving magnetic fields can
pull and push electrons. Some metals, like copper have electrons that are loosely held. They can
be pushed from their shells by moving magnets. Magnets and wire are used together in electric
generators.
How Does Battery Procedure Electricity?
A battery produces electricity using two different metals in a chemical solution. A chemical
reaction between the metals and the chemicals frees more electrons in one metal than in the
other. One end of the battery is attached to one of the metals; the other end is attached to the
other metal. The end that frees more electrons develops a positive charge and the other end
develops a negative charge. If a wire is attached from one end of the battery to the other,
electrons flow through the wire to balance the electrical charge. A load is a device that does work
or performs a job. If a load��such as a lightbulb��is placed along the wire, the electricity can do
work as it flows through the wire. In the picture above, electrons flow from the negative end of the
battery through the wire to the lightbulb. The electricity flows through the wire in the lightbulb and
back to the battery.
How Does Electricity Travel?
Electricity travels in closed loops, or circuits (from the word circle). It must have a complete path
before the electrons can move. If a circuit is open, the electrons cannot flow. When we flip on a
light switch, we close a circuit. The electricity flows from the electric wire through the light and
back into the wire. When we flip the switch off, we open the circuit. No electricity flows to the light.
When we turn a light switch on, electricity flows through a tiny wire in the bulb. The wire gets very
hot. It makes the gas in the bulb glow. When the bulb burns out, the tiny wire has broken. The path
through the bulb is gone. When we turn on the TV, electricity flows through wires inside the set,
producing pictures and sound. Sometimes electricity runs motors�in washers or mixers.
Electricity does a lot of work for us. We use it many times each day.
How is electricity generated?
A generator is a device that converts mechanical energy into electrical energy. The process is
based on the relationship between magnetism and electricity. In 1831, Faraday discovered that
when a magnet is moved inside a coil of wire, electrical current flows in the wire.
A typical generator at a power plant uses an electromagnet—a magnet produced by electricity—
not a traditional magnet. The generator has a series of insulated coils of wire that form a
stationary cylinder. This cylinder surrounds a rotary electromagnetic shaft. When the
electromagnetic shaft rotates, it induces a small electric current in each section of the wire coil.
Each section of the wire becomes a small, separate electric conductor. The small currents of
individual sections are added together to form one large current. This current is the electric
power that is transmitted from the power company to the consumer.
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
generate electricity. Steam turbines, internal-combustion engines, gas combustion turbines,
water turbines, and wind turbines are the most common methods to generate electricity. Most
power plants are about 35 percent efficient. That means that for every 100 units of energy that go
into a plant, only 35 units are converted to usable electrical energy.
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 most electricity generated in the United State comes from burning coal? In
2006, nearly half (49%) of the country's 4.1 trillion kilowatthours 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 2006, 20% 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 about two percent (2%) of all electricity generated in U.S.
electricity plants in 2006.
Nuclear power is a method in which steam is produced by heating water through a process called
nuclear fission. In a nuclear power plant, a reactor contains a core of nuclear fuel, primarily
enriched uranium. When atoms of uranium fuel are hit by neutrons they fission (split), releasing
heat and more neutrons. Under controlled conditions, these other neutrons can strike more
uranium atoms, splitting more atoms, and so on. Thereby, continuous fission can take place,
forming a chain reaction releasing heat. The heat is used to turn water into steam, that, in turn,
spins a turbine that generates electricity. Nuclear power was used to generate 19% of all the
country's electricity in 2006.
Hydropower, the source for almost 7% of U.S. electricity generation in 2006, is a process in which
flowing water is used to spin a turbine connected to a generator. There are two basic types of
hydroelectric systems that produce electricity. In the first system, flowing water accumulates in
reservoirs created by the use of dams. The water falls through a pipe called a penstock and
applies pressure against the turbine blades to drive the generator to produce electricity. In the
second system, called run-of-river, the force of the river current (rather than falling water) applies
pressure to the turbine blades to produce electricity.
Geothermal power comes from heat energy buried beneath the surface of the earth. In some
areas of the country, enough heat rises close to the surface of the earth to heat underground
water into steam, which can be tapped for use at steam-turbine plants. This energy source
generated less than 1% of the electricity in the country in 2006.
Solar power is derived from the energy of the sun. However, the sun's energy is not available full-
time and it is widely scattered. The processes used to produce electricity using the sun's energy
have historically been more expensive than using conventional fossil fuels. Photovoltaic
conversion generates electric power directly from the light of the sun in a photovoltaic (solar) cell.
Solar-thermal electric generators use the radiant energy from the sun to produce steam to drive
turbines. In 2006, less than 1% of the nation's electricity was based on solar power.
Wind power is derived from the conversion of the energy contained in wind into electricity. Wind
power, less than 1% of the nation's electricity in 2006, is a rapidly growing source of electricity. A
wind turbine is similar to a typical wind mill.
Biomass includes wood, municipal solid waste (garbage), and agricultural waste, such as corn
cobs and wheat straw. These are some other energy sources for producing electricity. These
sources replace fossil fuels in the boiler. The combustion of wood and waste creates steam that
is typically used in conventional steam-electric plants. Biomass accounts for about 1% of the
electricity generated in the United States.
What is a transformer?
To solve the problem of sending electricity over long distances, William Stanley 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.
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 do you measure electricity?
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 kilowatthour (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 kilowatthours (kWh).
Kilowatthours 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 watthours, or
0.2 kilowatthours, of electrical energy. See our Energy Calculator section to learn more about
converting units.
Sources: Energy Information Administration, Annual Energy Review 2006, August 2007 .
The National Energy Education Development Project, Intermediate Energy Infobook, 2006.
The National Energy Education Development Project, Intermediate Energy Infobook, 2006.
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