Job Info - Lesson 8 Flashcards
1) The conductors that carry the current to electrical devices and _____? equipment are the heart of all electrical systems. There are associated _____? whenever current flows through a conductor.
Utilization; Effects
2) Heat associated with the flow of current in a conductor is one of the most significant factors to be ______? in designing electrical systems. The conductor’s rating is dependent upon its type of electrical _____?
Considered; Insulation
3)Conductors are assigned a ____? ampacity that reflects the insulation’s ability to handle and dissipate heat under ____? conditions.
Specific; Varying
4) Conductors used in electrical systems are often defined by the material, if any, that is used to ____? the actual electrical conductor. Three classifications exist for electrical conductors: bare, _____?, and insulated.
Encase; Covered
5) Insulated conductors are the most common conductors installed in electrical systems. These conductors are constructed with a material that has been _____? by the NEC as a(an)_____? electrical insulation.
Identified; Recognized
6) There are numerous types of electrical insulations. The type of insulation selected depends upon the condition of ____? of the conductor. For example, a conductor for direct burial requires an insulation that is suitable for the conditions it is likely to be exposed to over the_____? of the conductor.
Use; Life
7) Conductors installed in wet locations require insulation that protects conductors from ____? exposure to moisture. When conductors are installed in wet locations, the insulated conductors and cables shall be either moisture-______? metal sheathed, be of a type listed for use in wet locations, or be of one of the types contained in 310.8(c).
Continuous; Impervious
8) The specific insulation types listed for use in wet locations contain the letter “W” in their prefix. The “W”_____? the conductor as having an insulation that is moisture-resistant and _____? for use in wet locations.
Identifies; Suitable
9) An important consideration in selecting conductor insulation type is the temperature limitations of the insulation. The three basic insulation temperature ratings listed for the conductors used for general wiring are _____? degrees C, 75 degrees C, and 90 degrees C. The maximum temperature that the conductor is exposed to along its _____? length shall be used when determining the temperature rating of a conductor.
60 degrees C; Overall
10) The common factors that can contribute to conductor insulation degradation because of excessive operating temperature are the _____? temperature in which the conductor insulation shall operate, the ____? heat created in the conductor as a result of current flow, the dissipation rate of the heat into the surrounding environment, and the heat generated by ____? current-carrying conductors.
Ambient; Internal heat; Adjacent
11) The two most common materials used for construction of electrical conductors are copper and aluminum. Copper has excellent _____? and therefore has a higher allowable _____? than a comparable aluminum conductor. Aluminum is not as good a conductor in terms of its allowable ______?, but is _____? and cheaper to install than copper.
Conductivity; Ampacity; Ampacity; Lighter
12) A factor to consider when installing electrical conductors is the weight of the conductors. Copper conductors installed in vertical ____? require support at ______? intervals than are required for aluminum conductors.
Raceways; shorter
13) Copper conductor are available as hard-drawn, medium-hard-drawn, and soft-drawn. Hard-drawn copper has the greatest _____?, but is difficult to work with. Because of the difficulty in shaping hard-drawn copper, its uses are ____?
Strength; Limited
14) Soft-drawn copper is easy to work with and can me installed in many different types of raceways and cable _____?. Most general _____? wires used in electrical distribution systems are made of soft-drawn copper.
Assemblies; Building
15) Aluminum conductors have been used extensively for a number of years in the ______? distribution and transmission field. More recently, aluminum conductors have found increasing applications in _______? electrical distribution systems.
Utility; Building
16) Despite the fact that aluminum is not as good a conductor as copper, its reduced______? is compensated by the considerable _____ savings in using aluminum conductors.
Conductivity; Cost
17) Because the surface of aluminum conductors oxidizes readily, terminations are generally made with the aid of joint______? designed to prevent the oxide from re-forming in the installation process. If the oxide is not prevented from re-forming, a high-resistance connection could occur which could lead to insulation failure at the _____?
Compounds; Termination
18) Conductors of different materials, like copper and aluminum, should not be terminated in a manner that causes the ____? metals to come in direct contact with each other unless the termination or splicing device is ____? for such use.
Dissimilar; Identified
19) Manufacturers provide torquing specifications for terminations. The termination should be tightened to those specifications to ____? that the connection is electrically______?.
Ensure; sound
20) Copper-clad aluminum offers a(an)_____? between the increased conductivity and termination qualities of copper conductors with the lighter weight and cost efficiency of aluminum conductors. Copper-clad conductors are constructed using a minimum of ______? % copper, which is bonded metallurgically to the aluminum.
Compromise; 10%
21) Conductors for electrical systems are either solid or stranded. Solid conductors are constructed of a(n)_____? piece of wire (strand). Stranded conductors are constructed of ______? wire (strands).
Single; Multiple
22) Chapter 9, Table _____? of the NEC lists conductor properties for common building wire. Notice that there are two listings for 8 AWG, and that under the header “conductors” there is a column for stranding. An 8 AWG conductor can be constructed from a single strand (solid) or from seven _____? strands.
8; Individual
23) List the maximum temperature ratings for each of the following cable insulation types.
a. RHW__________
b. XHHW(wet)________
c. MTW__________
d. TFE___________
e. UF___________
f. XHHW(dry)_________
g. THWN-2___________
a. 75 degrees C
b. 75 degrees C
c. 90 degrees C
d. 250 degrees C
e. 75 degrees C
f. 90 degrees C
g. 90 degrees C
24) The AWG table lists wire from size #_______?, the smallest, to #______?, the largest.
8, 4/0
25) A circular mil (CM) is the area of a circle with a diameter of ______?.
1 Mill
26) As the diameter of the wire increases, the AWG number______? (increases/decreases), and the resistance of the conductor _____? (increases/decreases).
Decreases; Decreases
27) Every electrical conducting material has a different resistance to current flow. In order to perform calculations to determine circuit resistance, you must know the _____? (abbreviated K) of a material.
Specific
The K of a material is defined as the resistance of the wire made from that material which is ______? long, and _____? in diameter.
1’ 1 mil
29) What happens to the resistance of most conductors as the temperature increases?
Resistance increases as well
30) The K factor of a copper conductor at 68 degrees is ______?
10.4
32) What is the difference between insulation types THW and THWN.
THWN has Nylon jackets
33) Conductors, type SIS, for switchboard wiring, have a maximum operating temperature of ______? degrees F
194 degrees F
34) THW wire is available in sizes from _____? to ______?
14 AWG to 4/0
36) Type XHHW conductor are listed for use in _____? and _____? locations.
Dry; Damp
37) Listed wire types designated with the suffix ____? shall be permitted to be used at a continuous 90 degree C operating temperature in both wet and dry locations.
-2