Module 4

  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)
    0.001 in.
  3. If a conductor has a diameter of 1/4 inch,
    what is its diameter in mils?
    250.0 mil
  4. What is the definition of a mil foot?
    • A conductor 1 foot in length with a
    • diameter of 1 mil
  5. 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
  6. A circular mil is defined as the area of a
    circle having what dimension?
    A diameter of 1 mil
  7. What is the definition of specific
    • The resistance of a unit volume of a
    • substance to the flow of current
    • expressed in ohms
  8. When a wire gauge is used to determine
    the size of a wire, the measurement
    should be made in what part of the
    In the slot
  9. What types of insulation are best suited
    for use in a high-temperature
    • Cotton, polytetrafluoroethylene, and
    • oiled paper
  10. What is the "ambient" temperature of a
    • It is the heat generated by external
    • sources and affecting a conductor’s
    • temperature
  11. Which of the following metals is the best
    conductor of current?
  12. Because its resistance changes very little
    with temperature changes, what
    conductor is best suited for use in
    measuring instruments?
  13. What definition best describes an
    insulating material?
    • A material that has a very high
    • resistance
  14. The dielectric strength of an insulating
    material is a measurement of the
    material's ability to resist electrostatic
    stress caused by what factor?
  15. Insulation resistance can best be defined
    as the ability of an insulating material to
    resist what action?
    Current leakage
  16. For a material to be a good insulator,
    what two properties are most important?
    • High dielectric strength and high
    • insulation resistance
  17. 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
  18. What is the NEC for a rubber heat resistance
  19. Latex rubber is a high-grade compound consisting of what percentage of unmilled grainless rubber?
  20. Plastic insulation is normally used for what levels of voltage?
    Medium to low
  21. When dealing with NEC type designators for thermoplastics, the letter "W" stands for what type of insulation?
  22. What nonmetallic material is most commonly used to protect wires and cables?
  23. What is the common name for woven covers?
  24. What percentage of tin is used in alloy lead sheathing?
  25. Why is the use of asbestos being discontinued as an insulating material in the Navy?
    It poses a health hazard to personnel
  26. What happens to asbestos insulation when it gets wet?
    It becomes a conductor
  27. What insulating materials are best suited for use with high voltage?
    Varnished cambric and oil
  28. What is the common name for enamel insulated wire?
    Magnet wire
  29. What are the basic requirements for a splice or terminal connection?
    To be mechanically and electrically effective
  30. The preferred method for removing insulation from most types of insulated wire is by using what tool?
    Wire stripper
  31. 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
  32. When multiconductor cables are spliced,why are the splices staggered?
    To reduce the overall size of the joint
  33. When is a rat tail joint normally used?
    When a branch circuit is required and a junction box is used to join conduit
  34. If a fluorescent light is to be attached to a branch circuit, which of the following splices should normally be used?
    Fixture joint
  35. When is a knotted tap joint normally used?
    When a branch circuit is joined to a continuous wire (main wire)
  36. Which of the following splices is NOT butted?
    Knotted tap joint
  37. Why is friction tape used over a splice?
    To provide a protective covering over the rubber tape
  38. Why would you use a crimped terminal instead of a soldered terminal?
    • Connections can be made more rapidly
    • Less operator skill is required
    • Connections are more uniform in construction
  39. When non insulated splices and terminal lugs are insulated, what types of insulation are most commonly used?
    Spaghetti and heat-shrinkable tubing
  40. When heat-shrinkable tubing is used,what is the maximum temperature to which the wire should be subjected?
  41. 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
  42. When aluminum terminals lugs or splices are installed, which of the following tools is generally recommended for use?
    Power crimping tool
Card Set
Module 4