chapter 11 magnetism electrical generation electrical transmission environmental impacts of high...
TRANSCRIPT
Chapter 11
Magnetism
Electrical Generation
Electrical Transmission
Environmental Impacts of High Voltage Lines
Standard Power Generation
Cogeneration and Combined Cycle Plants
Energy in the News
MagnetsLodestone or magnetite- first recognized by the Greeks in 500 BC. Used to make a compass needle.Like charges repel. Unlike charges repel. Magnetite= Fe3O4
Earths’ Magnetic Field Lines
Magnetic Particles Lined Up in Field
Dark:ElongatedMagneticParticlesPyrotite?
Light:RadiolarianSkeletons
What directionAre the Field lines?
Electrical Currents Make Magnetic Fields
Wire carrying current affects a compass needle:Original experiment by Oersted that discovered magnetic fields produced by electrical currents.
Coils of Wire (Solenoids)
Parallel Currents Attract
Parallel Currents in Loops Attract
Parts of an Electric Motor
Simple Electric Motor
Outside:Field magnet(permanentMagnet)
Inside:Rotating ElectromagnetReverses its field every half rotation
http://www.howstuffworks.com/motor2.htm
Detail of Electromagnet in Motor
Electromagnet is connected toA battery or other power source
Armature (green) allows the currentDirection to switch every 180Degree rotation, thus switchingThe North and south poles ofThe Electromagnet
Two Types of Current
Direct Current (DC): constant intensity and sign
Alternating Current(AC): varying intensity and sign
Some devices generate direct current, someGenerate alternating current.
A Moving Magnet Produces Current in the Wire
Electrical Generator
What type of current is made by this generator?What could turn the generator?
Electrical Generator: Second View
Wire is turnedIn the magneticField
Result: CurrentIn the wire.
Alternating Current from Generator
Cross Section of Gas TurbineGas turns blades on left: Right side connected to generator
High Voltage Transmission Lines
Typical Voltage:345,000 Volts
Why are the voltagesSo high?
Transformer: Changes Voltage and Current (not Power)
Two coils with alteratingCurrent. First coil inducesA current in the second coil.
Difference in voltage Proportional to difference inNumber of windings ofWire.
Vin * Iin = Vout * I out
Transformer on Power Pole
Why is the voltage steppedDown at the last minute, justBefore power is sent intoThe house?
Overall Electrical Distribution
Typical Magnetic and Electrical Fields
High voltage transmission lines: exposure MIGHT correlateWith leukemia and brain cancer. Studies very contradictory.
Costs of Electricity
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?
Turbines (Jet Engines)
How a Turbine Engine Works
Air EntersOn Right..
Shaft is Turned to Generate Electricity On Left.
http://www.howstuffworks.com/turbine.htm/
Detail of Turbine Combustion Area
Cogeneration Power Plant=Both Heat and Power Output
Separate Power and Heat
Generation
vs
Cogeneration
Efficiency of Cogeneration
Coal Gasification with CoGeneration