Transcript 10PRESEnergyChapter-5-sec

Section 3
Conservation of Energy
Objectives
• Explain how energy is conserved within a closed system.
• Explain the law of conservation of energy.
• Give examples of how thermal energy is always a result
of energy conversion.
• Explain why perpetual motion is impossible.
End of Slide
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Section 3
Conservation of Energy
Where Does the Energy Go / What Is It Used
For?
• Energy on a Roller Coaster To find out where a roller
coaster’s original potential energy goes, you have to think
about more than just the hills of the roller coaster. Friction
plays a part too.
•Friction is a force that opposes motion between two
surfaces that are touching.
•See how friction plays a part in roller coaster energy
conversions on the next slide.
End of Slide
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Section 3
Energy Conversions in a Roller Coaster
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Section 3
Conservation of Energy
Energy Is Conserved Within a Closed
System
• What Is a Closed System? A closed system is a group of
objects that transfer energy only to each other.
•No other energy is added to the system
• Law of Conservation of Energy
•According to the law of conservation of energy, energy
cannot be created or destroyed.
•Energy is changed from one form to another
End of Slide
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Section 3
Conservation of Energy
No Conversion Without Thermal Energy
•Some waste thermal energy always results from energy
conversions due to friction.
•Perpetual Motion? No Way! People have sometimes
tried to make a machine that would run forever without any
additional energy. This perpetual motion machine would put
out exactly as much energy as it takes in. But that’s
impossible, because some energy always changed to
thermal energy
• Making Conversions Efficient In terms of energy
conversions, energy efficiency is a comparison of the
amount of energy before a conversion with the amount of
useful energy after a conversion.
End of Slide
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 4
Energy Resources
Objectives
• Name several energy resources.
• Explain how the sun is the source of most energy on
Earth.
• Evaluate the advantages and disadvantages of using
various energy resources.
End of Slide
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Section 4
Energy Resources
Nonrenewable Resources – can not be replaced the
source will run out
• Uses of Fossil Fuels Oil and natural gas, shown on the
next slide, as well as coal, are the most common fossil
fuels.
•All fossil fuels contain stored energy from the sun, which
can be converted into other kinds of energy.
• Electrical Energy from Fossil Fuels One way to
generate electrical energy is to burn fossil fuels.
• Nuclear Energy Another way to generate electrical
energy is to use nuclear energy.
End of Slide
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Section 4
Formation of Fossil Fuels
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Section 4
Energy Resources
Renewable Resources – can be replaced, will not
run out
• Solar Energy Sunlight can be changed into electrical
energy through solar cells.
• Energy from Water The sun causes water to evaporate
and fall again as rain that flows through rivers. The
potential energy of water in a reservoir can be changed into
kinetic energy as the water flows through a dam.
• Wind Energy A wind turbine changes the kinetic energy
of the air into electrical energy by turning a generator.
End of Slide
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Section 4
Energy Resources
Renewable Resources continued
• Geothermal Energy Thermal energy caused by the
heating of Earth’s crust is called geothermal energy. Some
geothermal power plants pump water underground next to
hot rock. The water returns to the surface as steam, which
can then turn the turbine of a generator.
• Biomass Plants use and store energy from the sun.
Organic matter, such as plants, wood, and waste, that can
be burned to release energy is called biomass.
End of Slide
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Section 4
Energy Resources
The Two Sides to Energy Resources
• Advantages and Disadvantages All energy resources
have advantages and disadvantages.
• Choosing the Right Energy Resource Energy planning
in all parts of the world requires careful consideration of
energy needs and the availability and responsible use of
resources.
•Refer to page 146 Table 1
End of Slide
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Section 4
Energy Resources
How Electricity Is Generated From Different
Energy Sources
http://www.youtube.com/watch?v=20Vb6hlLQSg
End of Slide
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