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Energy
GCSE Physics
Forms of energy
3.5.1 describe energy transfers involving the
following forms of energy; chemical, heat,
electrical, sound, light, magnetic, nuclear, kinetic
and potential (gravitational and strain).
Reference
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Physics CCEA pg 1 and 2
Some Energy Facts…
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The U.S. has five percent of the world's
population and uses 23 percent of the world's
energy.
In one hour, your heart works hard enough to
produce the equivalent energy to raise almost 1
ton of weight 1 yard off :the ground.
A decrease of only 1% in industrial energy use
would save the equivalent of about 55 million
barrels of oil per year, worth about $1 billion
Basically Energy…
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In order to do work we must have a source of
energy.
When you eat a healthy nutri-grain bar you store
up energy which can then be used by your
muscles to physically do things. For a car to
move it requires a force which is provided by
mechanical work.
Whenever work is done energy is needed.
Top Ten Types of Energy
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Kinetic – energy an object has because it is moving.
Light – rays given off when an object glows.
Sound – vibrations caused when an object moves.
Electrical – produced when a current flows.
Nuclear – energy released when an atom splits.
Heat – moving molecules given out by fast vibrations.
Chemical – stored by food and fuels.
Elastic potential– energy stored in a stretched or squashed
object.
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Gravitational potential – energy an object has because of its
position above the ground.
Magnetic- energy which exists between magnetic materials.
Energy Transfer
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Energy tends to change form- take for example
the food we eat. The chemical energy is then
changed into kinetic energy (as well as other
types of energy) for our bodies to do useful
work!
Energy Transfer
The Dynamo
Output (wasted) energy-
heat/sound
Input energy
Kinetic
Output (useful) energy-
electrical/light
The Unit of Energy
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Energy is measured using the Joule or the
kiloJoule (1000 Joules)
Check out what energy values can do what
work…
Conservation of Energy
3.1.11 understand that energy is conserved and
describe energy changes in terms of the
principle of conservation of energy.
Conservation of Energy
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Reference- Page 2
Write out the law of conservation of energy
Another way of stating this law is that every
time energy is transferred the input energy will
be equal to the total output energy (sum of the
useful energy and wasted energy)
Example
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Every second a car transfers 200 kJ energy in the
petrol to 80 kJ of moving energy. Represent this
transfer in a diagram.
Output (useful) energyInput energy
Chemical
Kinetic
80 kJ
200 kJ
Output (wasted) energy-
Input Energy = Output Energy
200kJ = 80kJ + 120kJ
heat/sound
120 kJ
Try this question
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A power station uses 1,000,000 kJ of chemical
energy every second, but it only gives out
400,000 kJ of electrical energy each second.
What has happened to the input energy?
Draw an energy transfer diagram to represent
the transfer (include quantities and units).
Output (useful) energy-
Electrical
Input energy
Chemical
1 000 000 kJ
Transforms to
Kinetic
400 000 kJ
Output (wasted) energy-
The input energy has changed
form to kinetic and then to both
useful electrical energy and wasted
energy. The input energy and
output energy totals are equal as
energy is conserved.
Heat/Sound
600 000 kJ
Energy Resources
3.1.3 explain how energy resources such as wind
and fossil fuels are ultimately dependent on the
Sun’s energy.
Tracing Back… the source of all
energy
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Listening to a song, electrical energy sent to
your brain
Nerve
Cell
Electrical
Energy
Plants
Loud
Speaker
Sound
Energy
Fuel
Chemical Chemical
Energy
Energy
Plug and
wires
Electrical
Energy
Power
Station
Kinetic
Energy
… the Primary Source
The Sun
Nuclear
Energy
Energy Resources
3.1.2 recall that there is a variety of energy
resources, to include, oil, gas, coal, nuclear,
biomass, wind, wave, solar, geothermal, tidal and
hydroelectric and distinguish between renewable
and non-renewable.
Types of Energy Resources
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http://www.educapoles.org/loader.swf ?path=d
ocs/projects/flash_animations/energy_7_differ
ent_kinds_of_energy_061205.swf&lg=en
Energy Resources
3.1.4 describe the environmental implications of
the use of energy resources, limited to generation of electricity by
fossil fuels, nuclear fuels, hydroelectric power, wind farms, waves and
tides. Appreciate the effect on the environment of the use of these
energy resources, limited to the contribution of burning fossil fuels to
greenhouse effect (brief outline only), land/sea
use and nuclear waste.
3.1.5 evaluate the advantages and disadvantages
of using various energy resources to generate electricity. This should
take into consideration: reliability, how quickly the
different types of power station can respond
changes in demand, the costs of building,
to
operating and de-commissioning power stations and any additional
information, including quantitative information, with which they are
provided.
How is electricity generated?
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An electromagnet generator (a complex version
of a dynamo)
A turbine
Energy transfer in a Power Station
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http://www.eonuk.com/EnergyExperience/497.htm
Energy Resource Questions
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In class
Complete questions 5, 6, 8, 9, 14 and 15 on page
7 and 8
 For Homework
-
Complete questions 1- 3 on page 29
Geothermal Energy
The rocks not too far below the
surface are quite hot, 500°C
about 1 km down.
Geothermal
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In some areas there are 'hotspots' where the
temperature below the surface is very high. This
is usually near where the earth's tectonic plates
meet.
Geothermal Energy
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Water can be heated by these hot rocks which lie
beneath the Earth’s surface.
The steam from the hot water can be used to
turn a turbine and generate electricity!
Geothermal Energy
Advantages
Disadvantages
- Renewable energy - Deep drilling is
resource
very difficult
- Huge quantities
- Drilling can also be
of energy available expensive
Biomass
harvesting switchgrass
Biomass
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Biomass is a renewable energy source from
wood, manure, garbage and agricultural waste.
When biomass is burned, energy is released as
heat that can be transformed into electricity or
fuel.
Manure can also be turned into electricity using
the methane gas the solid manure gives off
when put into a digester.
http://www.energyquest.ca.gov/story/chapter10_flash/index.html
Biomass
Advantages
-It
makes sense to use
waste materials where we
can.
-The fuel tends to be cheap.
-Less demand on the
Earth's resources.
Disadvantages
-Collecting
the waste in
sufficient quantities can be
difficult.
-We burn the fuel, so it
makes greenhouse gases.
-Some waste materials are
not available all year round.
Crossword Puzzle
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http://www.energyquest.ca.gov/games/crosswo
rd_puzzles/renewable_energy.html
Efficiency
3.1.14 recall that efficiency is a measure of how
much energy is transferred in an intended way
and recall and use the relationships between
efficiency, input energy and output energy.
Efficiency
Reference Page 12
- Read page 12 for extra notes on Efficiency
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Efficiency is a measure of how
good a device is at changing energy
from one form to another.
All devices waste energy, so the
efficiency of a device is never 100%.
Energy efficient light bulbs are more efficient than normal
aste less energy, and more
light bulbs because they w____
lectrical energy that they are supplied with is
of the e______
ight energy and not h___.
converted into l___
eat
There is a formula that allows you to calculate the
efficiency of a device or of a process.
The efficiency formula
We can express efficiency mathematically using the
equation:
Efficiency =
Useful energy out
Total energy in
The efficiency formula is unusual because it has no units.
It is a number between 0 and 1 or a percentage %.
Useful energy measured in Joules (J)
Total energy measured in Joules (J)
Efficiency for a bulb
If you have a filament
bulb and it is supplied
with 100J of electrical
energy which it converts
to 45J of light energy.
a) How much energy is
wasted? 55J
b) In what form is the
energy wasted? heat
c) What is the efficiency of
the bulb?
Efficiency
= Useful
Total
= 45J/100J
= 0.45 or 45%