Ex. Module 4

Card Set Information

Ex. Module 4
2012-02-11 19:42:23

Show Answers:

  1. Why has a "unit size" for conductors been established?
    To compare the size and resistance of one conductor with that of another
  2. What is the decimal equivalent of one (1)mil?
    0.001 in
  3. What is the definition of a mil foot?
    A conductor 1 foot in length with a diameter of 1 mil
  4. A square mil is defined as the area of a
    square, the sides of which are each equal
    in length to what dimension?
    1 mil
  5. A circular mil is defined as the area of a
    circle having what dimension?
    A diameter of 1 mil
  6. What is the definition of specific resistance?
    The resistance of a unit volume of a substance to the flow of current expressed in ohms
  7. When a wire gauge is used to determine
    the size of a wire, the measurement
    should be made in what part of thegauge?
    In the slot
  8. What types of insulation are best suited
    for use in a high-temperature environment?
    Cotton, polytetrafluoroethylene, and oiled paper
  9. What is the "ambient" temperature of a
    It is the heat generated by external sources and affecting a conductor’s temperature
  10. Which of the following metals is the best
    conductor of current?
  11. Because its resistance changes very little
    with temperature changes, what conductor is best suited for use in measuring instruments?
  12. What definition best describes an insulating material?
    A material that has a very high resistance
  13. The dielectric strength of an insulating material is a measurement of the material's ability to resist electrostatic stress caused by what factor?
  14. Insulation resistance can best be defined
    as the ability of an insulating material to
    resist what action?
    Current leakage
  15. For a material to be a good insulator,
    what two properties are most important?
    High dielectric strength and high insulation resistance
  16. When rubber is used as the insulating
    material over a copper conductor, why is
    a thin coating of tin used between the
    two materials?
    • To prevent a chemical action from
    • taking place between the copper and rubber
  17. What is the NEC for a rubber heatresistance
  18. Latex rubber is a high-grade compound consisting of what percentage of unmilled grainless rubber?
  19. Plastic insulation is normally used for
    what levels of voltage?
    Medium to low
  20. When dealing with NEC type designators
    for thermoplastics, the letter "W" stands for what type of insulation?
  21. What is the common name for woven
  22. What percentage of tin is used in alloylead
  23. Why is the use of asbestos being
    discontinued as an insulating material in
    the Navy?
    It poses a health hazard to personnel
  24. What happens to asbestos insulationwhen it gets wet?
    It becomes a conductor
  25. What insulating materials are best suitedfor use with high voltage?
    Varnished cambric and oil impregnated paper
  26. What is the common name for enamel insulated wire?
    Magnet wire
  27. What are the basic requirements for a splice or terminal connection?
    To be mechanically and electrically effective
  28. The preferred method for removing
    insulation from most types of insulated
    wire is by using what tool?
    Wire stripper
  29. When a Western Union splice is used to
    connect two wires, why should the
    twisted ends of the wires be pressed
    down as close as possible to the straight
    portion of the wire?
    To prevent the wires from puncturing the tape covering
  30. When multiconductor cables are spliced,
    why are the splices staggered?
    To increase the strength of the individual splices
  31. When is a rattail joint normally used?
    When a branch circuit is required and a junction box is used to join conduit
  32. If a fluorescent light is to be attached to a
    branch circuit, which of the following
    splices should normally be used?
    Fixture joint
  33. When is a knotted tap joint normally used?
    When a branch circuit is joined to a continuous wire (main wire)
  34. Which of the following splices is NOT butted?
    Knotted tap joint
  35. Why is friction tape used over a splice?
    To provide a protective covering over the rubber tape
  36. When noninsulated splices and terminal
    lugs are insulated, what types of insulation are most commonly used?
    Spaghetti and heat-shrinkable tubing
  37. When heat-shrinkable tubing is used, what is the maximum temperature to which the wire should be subjected?
  38. When a large aluminum terminal lug or splice is installed, why is it NOT necessary to clean the aluminum wire?
    The wire is cleaned by the abrasive compound in the lug or splice
  39. When aluminum terminals lugs or splices are installed, which of the following tools is generally recommended for use?
    Power crimping tool
  40. Color codes are used on preinsulated terminal lugs and splices to indicate whatinformation?
    The wire sizes on which they are to be used