Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
32 Cards in this Set
- Front
- Back
|
Why has a "unit size" for conductors been established? |
To compare the size and resistance of one conductor with that of another
|
|
|
What is the decimal equivalent of one (1) mil?
|
0.001 in.
|
|
|
If a conductor has a diameter of 1/4 inch, what is its diameter in mils?
|
250.0 mil
|
|
|
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?
|
1 mil
|
|
|
A circular mil is defined as the area of a circle having what dimension?
|
A diameter of 1 mil
|
|
|
If you have a 12-strand conductor and each strand has a radius (one half the diameter) of 2/10 inch, what is the circular mil area of the conductor?
|
48,000 cir. mil
|
|
|
What is the definition of specific resistance?
|
The resistance of a unit volume of a substance to the flow of current expressed in ohms
|
|
|
What factor(s) must be known to compute the resistance of a conductor?
|
The length of the conductor
The cross-sectional area of the conductor The specific resistance of the substance of the conductor |
|
|
When a wire gauge is used to determine the size of a wire, the measurement should be made in what part of the gauge?
|
In the slot (not the semi-circular area)
|
|
|
What types of insulation are best suited for use in a high-temperature environment?
|
FEP, silicone rubber, and extruded polytetrafluoroethylene
|
|
|
What is the "ambient" temperature of a conductor?
|
It is the heat generated by external sources and affecting a conductor’s temperature
|
|
|
What conductors is best suited for use in measuring instruments because the resistance changes very little with temperature changes?
|
Manganin, Constantan
|
|
|
If a 75-ohm sample of copper wire at 0º C is heated to 30º C, what is the approximate total resistance? (The temperature coefficient of resistance of copper at 0º C is 0.00427).
|
84.61 ohms
|
|
|
What definition best describes an insulating material?
|
A material that has a very high resistance
|
|
|
The dielectric strength of an insulating material is a measurement of the material's ability to resist electrostatic stress caused by what factor?
|
Voltage
|
|
|
Insulation resistance can best be defined as the ability of an insulating material to resist what action?
|
Current leakage
|
|
|
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 two materials?
|
To prevent a chemical action from taking place between the copper and rubber
|
|
|
What is the NEC for a rubber heat-resistance compound?
|
RHH
|
|
|
Latex rubber is a high-grade compound consisting of what percentage of unmilled grainless rubber?
|
90%
|
|
|
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?
|
Moisture-resistant
|
|
|
When you work on synthetic insulated wiring, what safety precaution must be observed?
|
Avoid breathing the vapors when the insulation is heated
|
|
|
What nonmetallic material is most commonly used to protect wires and cables?
|
Fibrous braid
|
|
|
What is the common name for woven covers?
|
Loom
|
|
|
What percentage of tin is used in alloy-lead sheathing?
|
2%
|
|
|
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 impregnated paper
|
|
|
What is the common name for enamel-insulated wire?
|
Magnet wire
|
|
|
What types of conductor protection are normally used for shipboard wiring?
|
Wire braid armor and nonmagnetic steel tape
|
