chapter 8&9 questions

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Anonymous
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255217
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chapter 8&9 questions
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2014-01-05 13:30:53
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electricity
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electricity for refrigeration heating and air conditioning
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  1. what characteristics would apply to copper being used as a good conductor
    good mechanical strength, ability to resist corrosion, and easily joined together
  2. what is the disadvantage of using aluminum wire?
    corrodes easily
  3. what are four factors that should be considered in sizing circuit conductors
    voltage drop, insulation type, enclosure, and safety
  4. how would you determine the voltage drop in a circuit
    if there is a maximum voltage drop at the branch of the circuit of 3% but also the allowable voltage drop of most manufactures is 10%
  5. what is a disconnect switch
    it is a 2 or 3 pole switch mounted in an enclosure
  6. the most popular conductor used in the industry  is?
    copper
  7. what is the difference between a fusible disconnect switch and a non fusible disconnect switch
    fusible disconnect switch should be used with the proper fuse sizes while non fusible disconnect switch if means of protection for the wire or equipment is needed
  8. application determines what?
    the type of insulation surrounding the conductor
  9. how many hot legs would a three pole breaker supply to an appliance
    three hot legs and makes up a three phase circuit at the supply voltage
  10. national electrical code determines what
    the size and installation of an electrical circuit
  11. what is the purpose of a disconnect switch
    to disconnect power from the equipment
  12. what is the difference between a fusible load center and a breaker load center? which is primarily used in the industry today
    fusible load centers are older and you can find them when installing an air conditioning system to a older house while breaker load centers are in buildings and other structures today, in the industry breaker load centers are most common to find
  13. what is a circuit breaker?
    disconnecting power from the circuit
  14. how can a faulty circuit breaker be detected?
    either they cannot be reset or they open the circuit on a lower amperage than the rating
  15. how are circuit breakers attached to the main lugs of an electrical panel
    either with screws or with clips
  16. what is a distribution center and what is its primary purpose?
    distribution centers are designed to distribute the electrical supply to several places in large structures their use in largely confined to commercial and industrial applications
  17. a distribution center is used in?
    commercial and industrial
  18. what is true about the american wire gauge?
    there largest wire is No. 4/0 and wires larger than 4/0 are sized in circular mils
  19. true or false: fusible load centers are usually installed in residences today
    False
  20. what connects the breaker to the source of power in a breaker panel
    the main lugs
  21. what would you do in a situation where there is no spare opening in a breaker panel for the installation of equipment
    a breaker with two circuits can replace a standard one circuit breaker
  22. true or false: in all areas of the united states, air conditioning technicians can install the conductor from the distribution panel to the equipment
    false
  23. what is the purpose of a main breaker
    it is a supply system that divides its power feed to other breakers it is also the main power to all equipment
  24. what is magnetism
    the physical phenomenon that includes the attraction of object for iron and is exhibited by a permanent magnet or an electric current
  25. the strength that a motor produces by turning
    torque
  26. the area in which a magnetic force operates, around an electric wire, and an electric motor
    magnetic field
  27. true or false: a permanent magnet is a piece of material that has been magnetized and can hold its magnetic strength for a reasonable length of time
    true
  28. how is an electromagnet produced?
    it is produced by energy
  29. what produces the best electromagnet?
    soft iron
  30. unlike poles of a magnet ________ each other while the like poles____________ each other
    attract, repel
  31. what part does polarity play in the operation of an electric motor?
    it causes the rotor to move
  32. what part of a motor produces an inductive magnetic field within itself to facilitate the rotating motor?
    squirrel cage motor
  33. what part does the frequency of an alternating current play in the operation of an electric motor
    it directs the flow of current to the motor
  34. what are the five types of single phase motors used in the industry
    shaded pole, split phase, permanent split capacitor capacitor start capacitor run and capacitor start, electronically communicated
  35. list the motors starting torque from lowest to highest
    shaded pole, split phase, capacitor start, three phase
  36. what is the common use of a shaded pole motor?
    propeller fans
  37. how does a shaded pole operate?
    a current runs in the windings, the poles create a magnetic field and start rotating to give it a sufficient torque, and when it is at full speed it is negligible
  38. how can a shaded poole be reversed?
    the sat or must be reversed to change position and you have to disassemble the motor
  39. what determines the rotation of a shaded pole motor
    location of shaded pole
  40. what enables a split phase motor to develop enough torque to begin rotation
    it uses two windings to displace the phase and create the needed displacement between the run and start windings to produce rotation
  41. centrifugal switch does what?
    removes the starting winding from the electrical circuit of an open type split phase motor once it reaches 75% of its operating speed
  42. what are the three probable areas of trouble in a split phase motor?
    nearings, windings and centrifugal switch
  43. what is the unit of measurement for the strength of a capacitor?
    microfarad
  44. what is the purpose of a capacitor?
    to boost starting torque and increase running efficiency
  45. what is the difference between a running and a starting capacitor?
    a starting capacitor is built in a small case with a dielectric or a nonconductor of electric current while a running capacitor displaces heat is in a larger case but it is small
  46. explain the operation of a permanent split capacitor motor
    it is used on compressors where the refrigerant equalizes on the off cycle on direct fan motors it is a simple design and has a moderate starting torque
  47. how are a PSC motor and a capacitor start capacitor run motor similar
    both use a running capacitor
  48. what are the similarities between an open type split phase motor and a capacitor start motor
    both have a capacitor
  49. what is an advantage in using a three phase motor
    more dependable
  50. True or False: all starting apparatuses are mounted externally to the hermetic compressor shell
    True
  51. What is the process in trouble shooting any electric motor
    open up the motor checking the windings bar rings speed of winding and motor
  52. an ECM is a?
    three phase DC motor

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