Transcript Electrical Energy

Bellringer
Finish the following sentence:
“Energy is the ability to ____.”
Write your completed sentence in your
science journal. People often use the
words energy and power synonymously, but
they have specific meanings. What is the
distinction between energy and power?
Energy and Work: Working Together
• Energy is the ability to do work.
• Work is done when a force causes an
object to move in the direction of the
force. Work is a transfer of energy.
• Energy and work are expressed in
units of joules (J).
Kinetic Energy
Kinetic energy is the energy of
motion. All moving objects have
kinetic energy.
•
• Kinetic Energy Depends on Mass and Speed If you
know an object’s mass (m) and its speed (v), you can
calculate the object’s kinetic energy with the following
equation:
2
kinetic energy =
mv
2
Chapter M5
Potential Energy
• Potential energy is the energy an
object has because of its position.
• Gravitational Potential Energy The
amount of gravitational potential
energy that an object has depends
on its weight and its height.
Potential Energy, continued
•The equation to find gravitational
potential energy is:
gravitational potential energy = weight  height
Chapter M5
Mechanical Energy
• Mechanical energy is the total energy of
motion and position of an object. Both
kinetic energy and potential energy are
kinds of mechanical energy.
• The equation to find mechanical energy is:
mechanical energy = potential energy 
kinetic energy
Other Forms of Energy
• Thermal (Heat) Energy is all of the
kinetic energy due to random motion of
the particles that make up an object.
• Chemical Energy is the energy of a
chemical compound that changes as its atoms
are rearranged.
• Electrical Energy is the energy of moving
electrons.
• Sound Energy is caused by an
object’s vibrations.
• Light Energy is produced by the
vibrations of electrically charged particles.
• Nuclear Energy is energy that comes
from changes in the nucleus of an atom.
Chapter M5
Section 2 Energy Conversions
Bellringer
What do the following a plant, a Bunsen burner, and a
pendulum have in common? What are three other
objects that have same common link?
Write your answers in your science journal.
Kinetic Energy and Potential Energy
• An energy conversion is a change
from one form of energy to another. Any
form of energy can change into any other
form of energy.
• As the skateboarder on the next slide
travels up and down the half-pipe, his
energy changes back and forth between
kinetic energy and potential energy.
Chapter M5
Section 2 Energy Conversions
Chapter M5
Section 2 Energy Conversions
Kinetic Energy and Potential Energy,
continued
• Elastic Potential Energy Stretching a rubber band
stores elastic potential energy in the rubber band.
• When you let the rubber band go, it goes back to its
original shape. It releases its stored-up potential
energy as it does so.
Conversions Involving Chemical Energy
• Chemical energy is stored in the food you eat.
Your body uses this chemical energy to function.
• Energy Conversion in Plants The chemical
energy in the food you eat comes from the sun’s
energy. Plants use photosynthesis to convert light
energy into chemical energy, as shown on the
next slide.
Chapter M5
Section 2 Energy Conversions
Why Energy Conversions Are Important,
continued
• Conversions Involving Electrical Energy Some
common energy conversions that involve electrical
energy are shown in the table below.
Alarm clock electrical energy  light and sound energy
Battery
chemical energy  electrical energy
Light bulb
electrical energy  light and thermal energy
Blender
electrical energy  kinetic and sound energy
Chapter M5
Section 2 Energy Conversions
Chapter M5
Section 3 Conservation of Energy
Bellringer
Answer the following questions:
Where does the energy that makes a roller coaster car
move come from? Where does the energy go?
What does “All of the energy put into a process still
exists somewhere when the process has ended”
mean?
Write your answers in your science journal.
Where Does the Energy Go?
• Friction is a force that oppose motion
between two surfaces that are touching.
• For a roller coaster car to move, energy must be used to
overcome the friction between the car’s wheels and the track.
• As a result, not all of the car’s potential energy changes into
kinetic energy and not all of the car’s kinetic energy changes
back into potential energy.
Chapter M5
Section 3 Conservation of Energy
Chapter M5
Section 3 Conservation of Energy
Energy Is Conserved Within a Closed System
• A closed system is a group of objects that
transfer energy only to each other.
• The Law of Conservation of Energy states
that energy cannot be created or destroyed.
• The image below shows energy conservation in a light bulb.
Chapter M5
Section 3 Conservation of Energy
No Conversion Without Thermal Energy
• Any time one form of energy is converted into another
form, some of the original energy always gets
converted into thermal energy.
• The thermal energy due to friction that results from
energy conversions is not usually useful energy.
Chapter M5
Section 4 Energy Resources
Bellringer
Predict whether the following sources of energy are
renewable or nonrenewable.
sunlight
petroleum
coal
nuclear
wind
geothermal
Write and explain your predictions in your science
journal.
Nonrenewable Resources
• Nonrenewable resources cannot be
replaced or are replaced much more
slowly than they are used.
• Fossil fuels are nonrenewable energy resources that
formed from the remains of organisms that lived long ago.
Oil, natural gas, and coal are the most common fossil fuels.
Chapter M5
Chapter M5
Section 4 Energy Resources
Nonrenewable Resources, continued
• Electrical Energy from Fossil Fuels Electric
generators convert the chemical energy in fossil fuels
into electrical energy by the process shown below.
Nonrenewable Resources, continued
• Nuclear Energy Another way to
generate electrical energy is to use
nuclear energy.
• In a process called nuclear fission, the
nucleus of a radioactive atom is split into
two smaller nuclei, which releases nuclear
energy.
•Because the supply of radioactive elements is
limited, nuclear energy is a nonrenewable
resource.
Renewable Resources
• Renewable resources are naturally replaced
more quickly than they are used.
• Solar Energy Sunlight can be changed into
electrical energy through solar cells.
• Solar cells can be used in devices such as calculators.
They can also be placed on the roof of a house to provide
electrical energy.
Renewable Resources, continued
• Energy from Water The potential
energy of water in a reservoir can be
changed into kinetic energy as the water
flows through a dam.
• In a hydroelectric dam, falling water turns turbines. The
turbines are connected to a generator that changes
kinetic energy into electrical energy.
Renewable Resources, continued
• Wind Energy The kinetic energy of
wind can turn the blades of a
windmill or a wind turbine.
• A wind turbine changes the kinetic energy of the air into
electrical energy by turning a generator.
Renewable Resources, continued
• Geothermal Energy is thermal energy
caused by the heating of Earth’s crust.
•This energy can be converted into electrical energy at
geothermal power plants.
• Biomass is organic matter, such as
plants, wood, and waste, that can be
burned to release energy.
•Some countries depend on biomass for energy.