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Why has a "unit size" for conductors
- To compare the size and resistance of
- one conductor with that of another
What is the decimal equivalent of one (1)
If a conductor has a diameter of 1/4 inch,
what is its diameter in mils?
What is the definition of a mil foot?
- A conductor 1 foot in length with a
- diameter of 1 mil
A square mil is defined as the area of a
square, the sides of which are each equal
in length to what dimension?
A circular mil is defined as the area of a
circle having what dimension?
A diameter of 1 mil
What is the definition of specific
- The resistance of a unit volume of a
- substance to the flow of current
- expressed in ohms
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
What types of insulation are best suited
for use in a high-temperature
- Cotton, polytetrafluoroethylene, and
- oiled paper
What is the "ambient" temperature of a
- It is the heat generated by external
- sources and affecting a conductor’s
Which of the following metals is the best
conductor of current?
Because its resistance changes very little
with temperature changes, what
conductor is best suited for use in
What definition best describes an
- A material that has a very high
The dielectric strength of an insulating
material is a measurement of the
material's ability to resist electrostatic
stress caused by what factor?
Insulation resistance can best be defined
as the ability of an insulating material to
resist what action?
For a material to be a good insulator,
what two properties are most important?
- High dielectric strength and high
- insulation resistance
When rubber is used as the insulating
material over a copper conductor, why is
a thin coating of tin used between the
- To prevent a chemical action from
- taking place between the copper and
What is the NEC for a rubber heat resistance
Latex rubber is a high-grade compound consisting of what percentage of unmilled grainless rubber?
Plastic insulation is normally used for what levels of voltage?
Medium to low
When dealing with NEC type designators for thermoplastics, the letter "W" stands for what type of insulation?
What nonmetallic material is most commonly used to protect wires and cables?
What is the common name for woven covers?
What percentage of tin is used in alloy lead sheathing?
Why is the use of asbestos being discontinued as an insulating material in the Navy?
It poses a health hazard to personnel
What happens to asbestos insulation when it gets wet?
It becomes a conductor
What insulating materials are best suited for use with high voltage?
Varnished cambric and oil
What is the common name for enamel insulated wire?
What are the basic requirements for a splice or terminal connection?
To be mechanically and electrically effective
The preferred method for removing insulation from most types of insulated wire is by using what tool?
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
When multiconductor cables are spliced,why are the splices staggered?
To reduce the overall size of the joint
When is a rat tail joint normally used?
When a branch circuit is required and a junction box is used to join conduit
If a fluorescent light is to be attached to a branch circuit, which of the following splices should normally be used?
When is a knotted tap joint normally used?
When a branch circuit is joined to a continuous wire (main wire)
Which of the following splices is NOT butted?
Knotted tap joint
Why is friction tape used over a splice?
To provide a protective covering over the rubber tape
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
When non insulated splices and terminal lugs are insulated, what types of insulation are most commonly used?
Spaghetti and heat-shrinkable tubing
When heat-shrinkable tubing is used,what is the maximum temperature to which the wire should be subjected?
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
When aluminum terminals lugs or splices are installed, which of the following tools is generally recommended for use?
Power crimping tool