Job Info - Lesson 8

Question 1

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.

Answer 1

Utilization; Effects

Question 2

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 _____?

Answer 2

Considered; Insulation

Question 3

3)Conductors are assigned a ____? ampacity that reflects the insulation’s ability to handle and dissipate heat under ____? conditions.

Answer 3

Specific; Varying

Question 4

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.

Answer 4

Encase; Covered

Question 5

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.

Answer 5

Identified; Recognized

Question 6

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.

Answer 6

Use; Life

Question 7

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).

Answer 7

Continuous; Impervious

Question 8

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.

Answer 8

Identifies; Suitable

Question 9

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.

Answer 9

60 degrees C; Overall

Question 10

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.

Answer 10

Ambient; Internal heat; Adjacent

Question 11

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.

Answer 11

Conductivity; Ampacity; Ampacity; Lighter

Question 12

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.

Answer 12

Raceways; shorter

Question 13

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 ____?

Answer 13

Strength; Limited

Question 14

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.

Answer 14

Assemblies; Building

Question 15

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.

Answer 15

Utility; Building

Question 16

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.

Answer 16

Conductivity; Cost

Question 17

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 _____?

Answer 17

Compounds; Termination

Question 18

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.

Answer 18

Dissimilar; Identified

Question 19

19) Manufacturers provide torquing specifications for terminations. The termination should be tightened to those specifications to ____? that the connection is electrically______?.

Answer 19

Ensure; sound

Question 20

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.

Answer 20

Compromise; 10%

Question 21

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).

Answer 21

Single; Multiple

Question 22

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.

Answer 22

8; Individual

Question 23

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___________

Answer 23

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

Question 24

24) The AWG table lists wire from size #_______?, the smallest, to #______?, the largest.

Answer 24

8, 4/0

Question 25

25) A circular mil (CM) is the area of a circle with a diameter of ______?.

Answer 25

1 Mill

Question 26

26) As the diameter of the wire increases, the AWG number______? (increases/decreases), and the resistance of the conductor _____? (increases/decreases).

Answer 26

Decreases; Decreases

Question 27

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.

Answer 27

Specific

Question 28

The K of a material is defined as the resistance of the wire made from that material which is ______? long, and _____? in diameter.

Answer 28

1’ 1 mil

Question 29

29) What happens to the resistance of most conductors as the temperature increases?

Answer 29

Resistance increases as well

Question 30

30) The K factor of a copper conductor at 68 degrees is ______?

Answer 30

10.4

Question 31

32) What is the difference between insulation types THW and THWN.

Answer 31

THWN has Nylon jackets

Question 32

33) Conductors, type SIS, for switchboard wiring, have a maximum operating temperature of ______? degrees F

Answer 32

194 degrees F

Question 33

34) THW wire is available in sizes from _____? to ______?

Answer 33

14 AWG to 4/0

Question 34

36) Type XHHW conductor are listed for use in _____? and _____? locations.

Answer 34

Dry; Damp

Question 35

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.

Answer 35

-2