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Energy
Chapter 15
What is energy?
• Defined as the ability to
do work or the ability to
cause change.
• Measured in joules.
• Can occur in many forms.
Kinetic Energy
• Energy of
motion
• All moving
objects possess
kinetic energy
• Can change from
one type to
another
Factors which affect
kinetic energy:
• MASS
•K.E = ½
• VELOCITY
2
mv
Potential Energy
• Energy stored in an object due
to its position.
• Examples:
Gravitational potential
energy
• Dependant on the weight of the
object and its height above
some reference point.
• Formula:
Elastic Potential Energy
• Potential energy due to to the
physical distortion of an object.
• Depends on:
– Type of material
– Amount of distortion
Six main forms of
energy:
1. Mechanical energy
• Energy associated with motion:
2. Heat energy
• Internal motion of particles of
matter that often causes a
change in temperature.
3. Chemical energy
• Energy released or stored when
atoms are bonded together.
• Bonds can be broken to release
this energy.
4. Electromagnetic energy
• A form of energy that travels
through space in the form of
waves.
5. Nuclear energy
• Found in the nucleus of the atom
• Most concentrated form of
energy
• Reason for the brightness and
heat of the sun
• Nuclear link
6. Electrical energy
• Energy associated with
electrical charges or moving
electrons.
Energy conversions
• All forms of energy can change
from one form to another.
• Examples:
Conservation of Energy
•Energy can be
neither created
nor destroyed.
Calculations
• When friction is absent or small
enough to be ignored, total
mechanical energy = KE + PE
• Problems 1-3 page 458
Theory of Relativity
• Developed by
Albert Einstein
in 1905.
• Energy is
directly related
to mass.
• E = mc2
Energy Resources
• Nonrenewable:
– Cannot be replaced after being
used up. Examples:
Renewable resources
• Can be replaced in a relatively
short period of time. Examples:
• Hydroelectric
• Solar
• Wind
• Biomass
• Thermal
Hydroelectric energy
• Energy obtained
by damming a
river and
controlling the
flow.
• Potential energy
converted to
kinetic
converted to
electric
Solar energy
• Using sunlight as an energy
source on earth.
• A huge amount of energy
available, but problems include
storage and dependence on
climate.
Wind power
• Relatively
unlimited
amount of
energy
available.
• Problem: What
if it is not
windy?
Geothermal energy
• Using the heat beneath the
Earth’s surface.
Hydrogen fuel cells and
biomass
• Hydrogen fuel cells: a way to
generate electricity by reacting
hydrogen with oxygen.
• Biomass: using living organisms
to produce energy.
assignment
• Page 469-470
• 1-10, 12, 13, 14, 18, 21, 23, 25,
27, 28, 29, 32