Transcript Energy Transformations

Energy Transformations
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Changing Forms of Energy
•
•
Chemical, thermal, radiant, and electrical are
some of the forms that energy can have.
In the world around you, energy is
transforming continually between one form and
another.
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Changing Forms of Energy
• Forest fires are a dramatic example of an
environmental change that can occur naturally
as a result of lightning strikes.
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Tracking Energy Transformations
•As the mountain biker
pedals, his leg muscles
transform chemical
energy into kinetic
energy.
•Kinetic energy of his leg
muscles transforms into
kinetic energy of the
bicycle as he pedals.
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Tracking Energy Transformations
•Some of this energy
transforms into potential
energy as he moves up
the hill.
•Also, some energy is
transformed into thermal
energy.
•His body is warmer
because chemical energy
is being used.
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Tracking Energy Transformations
•Because of friction, the
mechanical parts of the
bicycle are warmer, too.
•Thermal energy is
almost always produced
by an energy
transformation.
•Thermal energy always
moves from the warmer
object to the cooler
object.
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Tracking Energy Transformations
•Because of friction, the
mechanical parts of the
bicycle are warmer, too.
The energy transformations
that occur
•Thermal
energy is
when people exercise, when cars run,
almost
always
produced
when living things grow and even
an energy
when stars explode, all by
produce
transformation.
thermal energy.
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Law of Conservation of Energy
• Energy is never created or destroyed.
• The only thing that changes is the form in which energy
appears.
– Example: When the biker is resting at the summit, all his
original energy is still around. Some of the energy is in the
form of potential energy, which he will use as he coasts down
the hill. Some of this energy was changed to thermal energy
by friction in the bike. Chemical energy was also changed to
thermal energy in the biker’s muscles, making him feel hot As
he rests, this thermal energy moves from his body to the air
around him. No energy is missing--- it can all be accounted
for.
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Potential energy is converted into kinetic energy.
• Before the yo-yo begins its fall
it has stored energy due to its
position. At the top it has its
maximum potential energy. As
it starts to fall the potential
energy begins to be changed
into kinetic energy. At the
bottom its potential energy has
been converted into kinetic
energy so that it now has its
maximum kinetic energy.
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Potential energy is converted into kinetic energy.
•A waterfall has both
potential and kinetic
energy. The water at the
top of Bridal Veil Falls has
stored potential energy.
When the water begins to
fall, its potential energy is
changed into kinetic
energy.
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Energy Changes Form
• A car engine burns gasoline,
converting the chemical
energy in gasoline into
mechanical energy. Solar cells
change radiant energy into
electrical energy. Energy
changes form, but the total
amount of energy in the
universe stays the same.
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Energy Changes Form
Hybrid cars that use an
electric motor and a
gasoline engine for
power are now
available. Hybrid cars
make energy
transformations more
efficient so the car can
travel farther on a
gallon of gas.
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Energy Changes Form
You wake up. It's a cool, sunny day,
You think you'll go for a bike ride. But
first you eat a good healthy breakfast.
You are taking the chemical energy
stored in food into your own body.
Any time energy is stored, it's called
potential energy. It's available for later
use. Without your needing to think
about it, the cells in your body will
break down the chemical bonds in the
food and release the energy in those
bonds. You'll use the energy to stay
warm, to grow, to keep your internal
organs working, and to move your
muscles.
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Energy Changes Form
And you are moving. You jump
up from the table, grab a jacket,
head out the door. You hop on
your bicycle.
The energy of motion is called
kinetic energy. As you pump
your legs, the bicycle starts to
roll. Your kinetic energy is being
transferred to the bicycle.
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Energy Changes Form
Back at home, you turn on a radio It runs on electrical energy which travels
along the wires that connect a power plant to your home. The electrical energy
used by the radio is converted into sound energy.
Sound is another form of kinetic energy--it's air in motion. You can move your
muscles to make sound too. For example, you can hit a drum, sing or shout, or
strum on a guitar. The guitar strings, vocal cords, or drumhead, once set in
motion, make the air around them move.
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Transforming Electrical Energy
• Every day you use
electrical energy. When
you flip a switch, or turn
on a radio or television,
or use a hair drier, you
are transforming
electrical energy to other
forms of energy.
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Generating Electrical Energy
Every Power plant works on the same principle---energy is used
to turn a large generator. A generator is a devise that transforms
kinetic energy into electrical energy. In fossil fuel power plants,
coal, oil, or natural gas is burned to boil water. As the hot water
boils, the steam rushes through a turbine, which contains a set of
narrowly spaced fan blades. The steam pushes on the blades
and turns the turbine, which in turn rotates a shaft in the
generator to produce the electrical energy.
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Power Plants
Almost 90 percent of the electrical energy generated in
the U.S. is produced by nuclear and fossil fuel power
plants. Other types of power plants include Hydroelectric
and wind. Hydroelectric power plants transform the
kinetic energy of moving water into electrical energy.
Wind power plants transform the kinetic energy of
moving air into electrical energy.
Sources of Electrical Energy in the U.S.
20%
Coal
Oil
3%
Gas
51%
9%
Hydro
Other Renewable
14%
Nuclear
3%
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Generating Electrical Energy
• A generator converts kinetic energy into
electrical energy.
• Burning fossil fuels produces thermal energy
that is used to boil water and produce steam.
• The PRIMARY energy is the fossil fuel. The
SECONDARY energy is the electrical energy.
• In a power plant, steam is used to spin a turbine
which then spins an electric generator.
• Green Energy is energy that is produced without
pollution. Examples are wind, solar, and water.
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Transforming Thermal Energy
• Chemical energy changes into thermal energy
when something burns.
• Electrical energy changes into thermal energy
when a wire that is carrying an electric current
gets hot.
• Thermal energy can be transformed into radiant
energy such as when a bar of metal is heated to
a high temperature, it glows and gives off light.
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Quick Review
• Changing Forms of Energy
– Heat usually is one of the forms of energy produced
in energy transformations.
– The law of conservation of energy states that energy
cannot be created or destroyed; it can only change
form.
– The total energy doesn’t change when an energy
transformation occurs.
– As an object rises and falls, kinetic and potential
energy are transformed into each other, but the total
energy doesn’t change.
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