ELECTRICAL WIRING 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 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
- - - + + + + + + - Positive Charged Atom Negative Charged Atom - - Too Few Electrons Too Many Electrons
1 2 3 Materials with Electrons in their outer rings make good conductors 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 - - - - - - - - - - - - - - - - - - - - - - - - -
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
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
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
Wattage “Watts” • What is a Watt? • • A unit of measure of electrical power • • A calculated quantity of electrical energy. • W = V x A • A kilowatt is 1000 watts. • A megawatt is 1,000,000 watts.
Horsepower HP You can change horsepower to watts rather easily by figuring 1,000 watts for each horsepowerof motor rating
Kilowatt-Hour Kwh A kilowatt-hour is the unit of measure by which electric power is marketed. Kilowatts x Hours = Kilowatt-Hours
Types of Current • DC – direct current • AC- alternating current
DC Current flows in one direction only. Used in flashlights, cameras, boats, automobiles
AC 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.
AC/DC Current 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.
Types of Power • Single phase 60- cycles per minute • Three phase 180 cycles per minute
Single Phase Three Wire Service The Current Alternates Directions 60 Cycles Per Second Supplies 120 and 240 Volts
Three Phase Four Wire Service The Current Alternates Direction 180 Cycles Per Second. Functions at Higher Voltages
Sources • Our power is generated for us compliments of our natural resources • Renewable and Non-renewable
Renewable Resources • Solar Energy • Tidal Energy • Geothermal Energy • Solid Wastes Energy • Water Energy • And Possibly Fast Growing Woods
Non-renewable Resources • Fossil fuels • Coal • Oil • Natural Gas • Non-sustainable Woods • Nuclear (uranium)
How are these resources converted to usable means? • Some type of mechanical generator!
Water Power Hydroelectric Generation- Accounts for approximately 11% of the U.S power supply
Steam Power • Fossil fuels • Nuclear Fission • Geothermal • Solid Waste • Wood There are several sources of steam power:
Fossil Fuels Coal, Oil, & Natural Gas
Coal Accounts for about 51% of steam power generated electricity Decreasing in quality Increasing in pollutants
Oil 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
Natural Gas Accounts for about 15% of electricity generated Quickly becoming the fuel of choice.
Reasons that natural gas is preferred • 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
NuclearFission Non-renewable Source Splitting uranium atoms produces a great deal of heat energy that is processed into electrical energy in nuclear plants.