Download AG-AG-AMI-01421-3.3 pp Basic Electrical Terms and TheorypvAG

Electrical Terms and Theory
To accompany the Georgia Agriculture Curriculum
Course: AG-AMI-01.421
Agricultural Mechanics I
Unit 3: Electrical Wiring
2010
VGP
The Atom
The Basic Structure of an Atom
Atoms will have the same
number of Electrons in the
orbit as there are Protons
in the center.
Electrons (29 total)
Valence Ring
(Outer Ring)
Protons (29 total)
A Copper Atom
Balanced Atom
Equal Number of Protons and Electrons
Unbalanced Atom
Number of Protons and Electrons is Unequal
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Circuit
Positive Charged Atom
Negative Charged Atom
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Too Few Electrons
Too Many Electrons
Materials with Electrons in their outer rings make
good conductors
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2
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Because the Electrons are easily dislodged from their orbit
and pushed to the atom next to them. (Electron flow)
Materials which hold their electrons closely are good
Insulators
Electrons are not easily dislodged from their orbit
and pushed to the atom next to them.
Electrons flow from atom to atom
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Parallel vs. Series Circuits
Electrical Circuit vs. Water
Amperes
“AMP”
What is an Ampere or (Amp)?
• A unit of measure of the rate of flow of
electricity. “Currrent”
•One Amp = 6,280,000,000,000,000,000
(6.28 Quintillion electrons passing a point
in one second.)
•Symbol: A or I
Ammeter
Voltage
“Volts”
What is a Volt?
•An Electromotive Force.
•A unit of measure of electrical pressure
•The force required to move one amp of electricity through a
resistance of one ohm.
•Symbol: E or V
•Voltages Available: 120 and 240
Voltmeter
Resistance
“Ohm”
What is an Ohm?
•A measure of the resistance of electrons to flow in a
material.
•The resistance to the movement of electrons.
•Relates to four Factors –Material, Diameter, Length, and
Temperature.
•Symbol: R or O
Ohmmeter
Wattage
“Watts”
What is a Watt?
• A unit of measure of electrical power
• A calculated quantity of electrical energy.
•W=VxA
• A kilowatt is 1000 watts.
• A megawatt is 1,000,000 watts.
Wattmeter
Horsepower
HP
You can change horsepower to watts rather easily by
figuring 1,000 watts for each horsepower of motor rating
Kilowatt-Hour
Kwh
A kilowatt-hour is the unit of measure by which electric power is marketed.
Kilowatts x Hours = Kilowatt-Hours
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DC – direct current
AC- alternating current
Current flows in one direction only.
Used in flashlights, cameras, boats, automobiles
Current flows in one direction ½ of the cycle then reverses for
the 2nd ½ of the cycle.
Used in most home appliances, t.v., radio, computers.
Figure 1-B-29. (a) DC current always flows in one direction,
unchanging, as through this automotive headlight bulb. (b) AC
current flows in one direction for one-half cycle, then reverses
direction for one-half cycle, completing a cycle. This action
occurs 60 times per second. (60 HZ)
Hertz
A hertz is an international measure of electrical
frequency, with 1 Hz being one cycle per second.
Electrical outlets have different frequencies in
different countries. For instance, while outlets in the
United States, Canada and Aruba have frequencies of
60 Hz, outlets in China and Denmark are 50 Hz.
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Single phase 60- cycles per minute
Three phase 180 cycles per minute
Three Wire Service
The Current Alternates Directions 60
Cycles Per Second
Supplies 120 and 240 Volts
Four Wire Service
The Current Alternates Direction 180
Cycles Per Second.
Functions at Higher Voltages
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Our power is generated for us compliments
of our natural resources
Renewable and Non-renewable
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Solar Energy
Tidal Energy
Geothermal Energy
Solid Wastes Energy
Water Energy
And Possibly Fast Growing Woods
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Fossil fuels
◦ Coal
◦ Oil
◦ Natural Gas
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Non-sustainable Woods
Nuclear (uranium)
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Some type of mechanical generator!
Hydroelectric GenerationAccounts for approximately 11% of
the U.S power supply
There are several sources of steam
power:
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Fossil fuels
Nuclear Fission
Geothermal
Solid Waste
Wood
Coal, Oil, & Natural Gas
Accounts for about 51% of steam
power generated electricity
Decreasing in quality
Increasing in pollutants
Accounts for 2% of electricity generated.
Once preferred over coal for ease of
handling and for how clean it burned
In lesser supply now so is a less
desirable source
Accounts for about 15% of electricity
generated
Quickly becoming the fuel of choice.
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Use of existing technology
Low capital cost
Short license procedures
Ability to add small amounts of distributed
generation for growth needs without building
huge expensive plants
Efficiency and cost effectiveness
Lower environmental impacts
Non-renewable Source
Splitting uranium atoms produces a great deal of
heat energy that is processed into electrical
energy in nuclear plants.
Renewable Resource
Utilizes the Earth’s inner heated rocks to
heat water that reaches these areas
through seismic faults. This water is
turned to steam them captured to
operate steam-powered generators.
Renewable resource
Uses heat generated from burning solid
municipal waste to heat water to operate steam
powered generators.
Scrap wood is used to power boilers
in some mills, but this is a little used
practices, obviously for conservation
purposes.
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Wind- used near coastal areas and high
ridges
Thermal Conversion- mirrors reflect
sunlight to heat water
Photovoltaic Conversion- Solar power
converted directly into electricity
Tidal – Waves used to turn turbines for
generation
Fuel cells- Products of the space age;
use fossil fuels without combustion
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Fusion- Adding an extra oxygen atom to H2O
creates heat for steam
Biogas- captured methane from landfills
Chemical- batteries (primary cells and
storage cells)- ex. Dry cell, nickel-cadmium,
lead acid, and gel
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Power is generated by one of the
previously mentioned methods and stored.
It is transported as needed to a step up
transformer substation.
It is then carried via transmission lines to
a step down transformer substation.
Distribution lines carry it to consumers
homes and businesses.
Step-up transformers are
used at the power plant to
increase the voltage and
decrease the amperage. As a
Step-up transformers are used at
the power plant to increase the
voltage
and
decrease
the
amperage. As a result, efficiency is
increased and smaller transmission
wires can be used.
y is increased and smaller
transmission wires can be
used.
Step-up transformers are
used at the power plant to
increase the voltage and
decrease the amperage. As a
Before the power can be used, the
voltage is stepped down and the
amperage is stepped up.
y is increased and smaller
transmission wires can be
used.