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