Ag Mechanics, Ag Structures, Ag Powers, and Ag Technology AMI’s Days 11-15 If you are working on a mechanical/structural project at home/work/or with family that pertains to one of the above subject areas, you can take pictures of the project throughout the process and email them to me and I will take this for a grade. All others, complete the assignments attached and email the answers to me. Instructions: Days 11-15: Define the vocabulary words at the first of the packet and answer the questions at the end of the packet. Email all answers or pictures to me [email protected]
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Ag Mechanics, Ag Structures, Ag Powers, and Ag Technology AMI’s
Days 11-15
If you are working on a mechanical/structural project at home/work/or with family
that pertains to one of the above subject areas, you can take pictures of the
project throughout the process and email them to me and I will take this for a
grade.
All others, complete the assignments attached and email the answers to me.
Instructions:
Days 11-15: Define the vocabulary words at the first of the packet and answer the
Resistance is the tendency of the wire to resist the flow of electrons or current throughthe wire. Within a circuit, electrical resistance is dependent upon size, length, and the materialof the conductor. Smaller diameter wire will have more resistance than larger. The longer thewire in the circuit, the more resistance. Finally, compared with other metals, silver, copper,and aluminum offer the least resistance to the flow of an electrical current. Resistance is mea-sured in ohms. The relationship of ohms (R), volts (E), and amps (I) is E = I × R.
Direct current (DC) flows in one direction in a circuit. It is often used in automobiles andtractors. Nearly all the electrical current produced for home and farm use in the United Statesis 60-cycle alternating current (AC). The direction of flow of AC is reversed by a generator 120times per second. Each pair of reversals or one back-and-forth motion is called a cycle. Thus,there are 60 cycles per second.
Phase is a timed source of electricity through a conductor. Single-phase is current fromone source with three wires: one hot, one neutral, and one ground. Three-phase is actuallythree single phases combined. The three are combined to give equally spaced peak voltages.Three hot wires and a fourth neutral wire or just three hot wires may by used, depending onthe system design.
SAFETY PRACTICES
Electricity is a very safe and economical source of power. However, injury and loss of life
can occur quickly when electricity is improperly used. Property can be destroyed by electrical
failures and fires. Some electrical safety practices are listed here.
� Avoid damp working areas. Never handle electrical equipment with wet hands or whilestanding in a wet or damp place.
� Protect each circuit. Be certain that each circuit is protected with either a circuit breakeror a fuse of proper amperage.
� Ground each circuit properly. Each circuit must have a ground (neutral) wire and agrounding wire to be properly grounded.
� Use ground-fault circuit interrupters (GFCIs). To protect the operator who works out-side or in damp locations, make sure the electrical source is protected by a ground-faultcircuit interrupter.
� Ground electrical equipment. All 120-volt electrical equipment should be equipped witha three-prong grounding-type plug or be double insulated. Never cut off a groundingprong just to make the connection work.
� Disconnect the main switch. Before making any repairs on an electrical circuit, alwaysmake certain the current has been disconnected to that circuit at the circuit breaker.
� Correct the source of trouble. Before resetting a circuit breaker or replacing a blown fuse,correct the cause of the trouble. Repair or replace any equipment that gives a shock whenit is used.
� Purchase safe equipment. Select portable electrical equipment that is grounded with athree-prong plug or is double insulated. Look for the “UL” label, indicating that theequipment has been tested and approved by Underwriters Laboratories, Inc.
E-unit: Introducing Electricity and Electrical Safety
� Review the local electrical code.When rewiring a building, fol-low the local electrical code.
� Seek professional help instead ofusing trial-and-error methodswhen electrical devices do notfunction properly.
� Avoid plumbing hazards. Do notlocate switches or light fixturesnear plumbing fixtures.
� Inspect and repair cords periodi-cally. Inspect all extension cordsand electrical appliance cords periodically for exposed wires, faulty plugs, poor insulation,and loose connections. Correct all hazards found on electrical cords.
� Open circuits with switches. Never pull a plug from an outlet while the equipment is inoperation. This creates an arc and will eventually foul the plug or the outlet, which cancause electrical shock or a possible fire.
� Never make temporary repairs. Make sure all repairs are as good as new. When splicingwires, be sure all strands are twisted together, the connections are strong, and the splice isfully insulated.
� Use electrical cords safely. Donot hang electrical cords on nailsor run them under rugs oraround pipes. Avoid using exten-sion cords as permanent wiringinstallations.
� Do not overload circuits. Whennew equipment is installed,make sure it is protected by a cir-cuit of proper amperage rating.
� Unplug electrical tools. Do notleave a tool plugged in when it isnot in use, unless it is designedfor continuous operation.
Summary:
� Electricity is the flow of electrons in a conductor. The path through which elec-trons flow is called a circuit. Two kinds of electricity are static and current. Currentelectricity may be in the form of direct current or alternating current.
Electrical service begins with a power source, which is usually a large generatingplant with a system of lines to get the electricity to the user. Materials needed to
E-unit: Introducing Electricity and Electrical Safety
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provide service include conductors and insulators. Service is provided to users ofelectricity by three wires. A meter at the service entrance measures the electricitybeing used. A service panel houses the circuit breakers for the system and distrib-utes power to individual circuits throughout the system.
Various terms are important in understanding electricity. Some of those terms arevoltage, amperage, watts, resistance, ohms, and phase.
Injury and loss of life can occur quickly when electricity is improperly used. Prop-erty can be destroyed by electrical failures and fires.
Checking Your Knowledge:
� 1. What is electricity?
2. How do direct and alternating current compare?
3. How does electricity get from the power source to the user?
4. What are the meanings of voltage, amperage, watts, resistance, ohms, and phase?
5. What are some electrical safety practices?
Expanding Your Knowledge:
� Conduct an electrical safety check in your home. Look for overloaded outlets, oldcords, and similar hazards. Take steps to correct the problems.
heating of the pipe. A propane torch may be the fastest method for thawing iron or copper
pipe. When using a torch, move it constantly back and forth, and remove the flame every cou-
ple of minutes or so to let the pipe cool. Also, be sure to start by heating the end of the pipe
nearest the faucet instead of starting at the middle of the pipe.
Other methods of thawing pipes include wrapping pipes with rags and pouring on boiling
water, warming pipes with heat lamps, and heating pipes with electrical resistance from an arc
welder. Note that both the welder and the torch methods for thawing pipes may only be used
on iron and copper pipes.
If the frozen pipe is a drain rather than a supply pipe, it can be thawed easily by running hot
water into the drain. If this does not work after several minutes, pour in a mixture of chemical
drain cleaner and cold water.
Summary:
� Clogged sink or toilet drains are the most common plumbing problems. When allsinks and toilets have a drain problem, the sewer line is probably clogged. If thedrain problem is confined to one sink or toilet, clear the blockage.
E-unit: Maintaining and Repairing Plumbing Systems
Every 3 to 4 months, the water heater should be drained of any accumulated sedi-ment. Most water heaters have a pressure relief valve that should be opened period-ically. In addition, the bathroom stool should be checked periodically. A flush toilethas two major parts: the flush tank and bowl. If you have a septic tank, it should beinspected every year or two.
Fixing dripping faucets and leaking pipes yourself can save money and avoid delays.Faucets are either washer type or washer-less type.
To prevent water pipes from freezing, wrap them with insulation and/or heat tape.Thaw the ice by warming pipes with a propane torch, boiling water, heat lamps, andelectrical resistance from an arc welder.
Checking Your Knowledge:
� 1. How are sinks unclogged?
2. How are toilets unclogged?
3. How are water heaters maintained?
4. How are dripping faucets repaired?
5. How should frozen pipes be thawed?
Expanding Your Knowledge:
� Check your home plumbing system for leaky faucets and clogged drains. Has thewater heater been maintained? Are pipes vulnerable to freezing temperatures due tolack of insulation? Follow up by correcting problems.