Magnetism

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Chapter 11
Magnetism Electrical Generation Electrical
Transmission Environmental Impacts of High
Voltage Lines Standard Power Generation Cogenera
tion and Combined Cycle Plants
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Energy in the News
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Magnets
Lodestone or magnetite- first recognized by the
Greeks in 500 BC. Used to make a compass
needle. Like charges repel. Unlike charges
repel. Magnetite Fe3O4
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Earths Magnetic Field Lines
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Magnetic Particles Lined Up in Field
Dark Elongated Magnetic Particles Pyrotite? Ligh
t Radiolarian Skeletons What direction Are the
Field lines?
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Electrical Currents Make Magnetic Fields
Wire carrying current affects a compass
needle Original experiment by Oersted that
discovered magnetic fields produced by electrical
currents.
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Coils of Wire (Solenoids)
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Parallel Currents Attract
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Parallel Currents in Loops Attract
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Parts of an Electric Motor
http//www.howstuffworks.com/motor2.htm
Simple Electric Motor Outside Field
magnet (permanent Magnet) Inside Rotating
Electromagnet Reverses its field every half
rotation
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Detail of Electromagnet in Motor
Electromagnet is connected to A battery or other
power source Armature (green) allows the
current Direction to switch every 180 Degree
rotation, thus switching The North and south
poles of The Electromagnet
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Two Types of Current
Direct Current (DC) constant intensity and
sign Alternating Current(AC) varying intensity
and sign Some devices generate direct current,
some Generate alternating current.
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A Moving Magnet Produces Current in the Wire
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Electrical Generator
What type of current is made by this
generator? What could turn the generator?
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Electrical Generator Second View
Wire is turned In the magnetic Field Result
Current In the wire.
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Alternating Current from Generator
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Cross Section of Gas Turbine
Gas turns blades on left Right side connected to
generator
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High Voltage Transmission Lines
Typical Voltage 345,000 Volts Why are the
voltages So high?
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Transformer Changes Voltage and Current (not
Power)
Two coils with alterating Current. First coil
induces A current in the second coil. Difference
in voltage Proportional to difference in Number
of windings of Wire. Vin Iin Vout I out
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Transformer on Power Pole
Why is the voltage stepped Down at the last
minute, just Before power is sent into The
house?
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Overall Electrical Distribution
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Typical Magnetic and Electrical Fields
High voltage transmission lines exposure MIGHT
correlate With leukemia and brain cancer.
Studies very contradictory.
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Costs of Electricity
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Costs of Transmitting Energy
Transmission lines most expensive way to move
energy Moving energy in gas pipelines, by barge
or by rail is much Cheaper. ( cost is about
half). Why?
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Turbines (Jet Engines)
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How a Turbine Engine Works
http//www.howstuffworks.com/turbine.htm/
Air Enters On Right.. Shaft is Turned to
Generate Electricity On Left.
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Detail of Turbine Combustion Area
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Cogeneration Power PlantBoth Heat and Power
Output
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Separate Power and Heat Generation vs
Cogeneration
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Efficiency of Cogeneration
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Coal Gasification with CoGeneration