Job Information Level 2: Lesson 1 Building Wire Construction and Insulation Properties Flashcards
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.
Select one:
a.
relay / responses
b.
service / effects
c.
utilization / effects
d.
utilization / responses
utilization / effects
? associated with the flow of current in a conductor is one of the most significant factors to be considered in designing electrical systems. The conductor’s rating is dependent upon its type of ? .
Select one:
a.
Heat / electrical insulation
b.
Heat / voltage
c.
Voltage / electrical insulation
d.
Voltage / heating
Heat / electrical insulation
Conductors are assigned a ? ampacity that reflects the insulation’s ability to handle and dissipate heat under ? conditions.
Select one:
a.
high / ideal
b.
specific / ideal
c.
specific / varying
d.
variable / specific
specific / varying
Conductors used in electrical systems are often defined by the material, if any, that is used to encase the actual electrical conductor. Three classifications exist for electrical conductors; they are ? , ? , and ? .
I. armored II. bare III. coated IV. covered V. insulated VI. flat conductor VII. Machine tool wire VIII. thermoplastic
Select one:
a.
I., II., and IV.
b.
II., III., and IV.
c.
II., IV., and V.
d.
III., IV., and VI.
e.
III., IV., and VIII.
f.
IV., V., and VII.
II., IV., and V.
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 ? electrical insulation.
Select one:
a.
approved / certified
b.
approved / listed
c.
identified / certified
d.
identified / recognized
identified / recognized
There are numerous types of electrical insulations. The type of insulation selected depends upon the condition ? 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.
Select one:
a.
of use / length
b.
of use / life
c.
or type / length
d.
or type / life
of use / life
When conductors are installed in wet locations, the insulated conductors and cables shall be either moisture-impervious metal-sheathed, be of a type listed for use in wet locations, or be of one of the types contained in ? .
Select one:
a.
300.7(A)
b.
300.9
c.
310.1 Informational Note
d.
310.10(C)(2)
310.10(C)(2)
The specific insulation types listed for use in wet locations contain the letter ? in the type designator.
Select one:
a.
“M”
b.
“N”
c.
“T”
d.
“W”
“W”
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 ? . The ? temperature that the conductor is exposed to along its entire length shall be used when determining the temperature rating of a conductor.
Select one:
a.
40°C, 75°C, and 90°C / maximum
b.
60°C, 75°C, and 90°C / maximum
c.
40°C, 75°C, and 90°C / minimum
d.
60°C, 75°C, and 90°C / minimum
60°C, 75°C, and 90°C / maximum
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 adjacent current-carrying conductors.
Select one:
a.
adjacent / external
b.
ambient / external
c.
ambient / internal
d.
highest / internal
ambient / internal
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.
Select one:
a.
ampacity / resistance
b.
conductivity / ampacity
c.
conductivity / voltage
d.
resistive characteristics / voltage
conductivity / ampacity
A factor to consider when installing electrical conductors is the weight of the conductors. Copper conductors installed in ? require support at ? intervals than are required for aluminum conductors.
Select one:
a.
horizontal raceways / longer
b.
horizontal raceways /shorter
c.
vertical raceways / longer
d.
vertical raceways / shorter
vertical raceways / shorter
Copper conductors are available as hard-drawn, medium-hard-drawn, and soft-drawn. Hard-drawn copper has the greatest strength, but is difficult to work with. Because of the difficulty in shaping hard-drawn copper, its uses are limited.
Select one:
True
False
True
Soft-drawn copper is easy to work with and can be installed in many different types of raceways and cable ? . Most general building wires used in electrical distribution systems are made of soft-drawn copper.
Select one:
a.
assemblies
b.
distribution systems
c.
jackets
d.
management systems
assemblies
Aluminum conductors have been used extensively for a number of years in the utility distribution and transmission field. More recently, aluminum conductors have found increasing applications in building electrical distribution systems.
Select one:
True
False
True
Despite the fact that aluminum is not as good a conductor as copper, its reduced ? is compensated by the considerable cost savings in using aluminum conductors.
Select one:
a.
conductivity
b.
resistance
c.
size
d.
weight
conductivity
Because the surface of aluminum conductors oxidizes readily, terminations are generally made with the aid of ? designed to prevent the oxide from re-forming in the installation process.
Select one:
a.
copper coating
b.
dissimilar metals
c.
joint compounds
d.
stainless steel coating
joint compounds
Conductors of different materials, like copper and aluminum, should not be terminated in a manner that causes the dissimilar metals to come in direct contact with each other unless the termination or splicing device is ? for such use.
Select one:
a.
accepted
b.
coated
c.
identified
d.
terminated
identified
Manufacturers provide ? specifications for terminations. The termination should be tightened to those specifications to ensure that the connection is electrically sound.
Select one:
a.
bolting
b.
clading
c.
material
d.
torquing
torquing
Copper-clad conductors are constructed using a minimum of ? copper, which is bonded metallurgically to the aluminum.
Select one:
a.
8%
b.
10%
c.
18%
d.
20%
10%
Solid conductors are constructed of a single piece of wire (strand). Stranded conductors are constructed of multiple wire (strands).
Select one:
True
False
True
Chapter 9, Table ? of the NEC lists conductor properties.
Select one:
a.
1
b.
4
c.
8
d.
9
8
Match the maximum temperature ratings for each of the following cable/conductor insulation types. Note: Some of the following cable types might have more than one insulation type listed.
I. 40°C II. 60°C III. 60°C and 90°C IV. 75°C V. 90°C VI. 250°C VII. 60°C and 75°C
RHW = XHHW (wet) = MTW = TFE = UF = XHHW (dry) = THWN-2 =
iv, iv, iii, vi, vii, v, v
In Table 8, Chapter 9 of the NEC, conductors are listed from size # ? , the smallest, to # ? , the largest.
Select one:
a.
14 AWG / 1,000 kcmil
b.
14 AWG / 2,000 kcmil
c.
18 AWG / 1,000 kcmil
d.
18 AWG / 2,000 kcmil
18 AWG / 2,000 kcmil
A circular mil (CM) is the area of a circle with a diameter of ? .
Select one:
a.
one centimeter
b.
one mil
c.
one micron
d.
πr2
one mil
As the diameter of the wire increases, the AWG number ? , and the resistance of the conductor ? .
Select one:
a.
decreases / decreases
b.
decreases / increases
c.
increases / decreases
d.
increases / increases
decreases / decreases
calculations to determine circuit resistance, you must know the ? (abbreviated K) of a material.
Select one:
a.
conductance
b.
reactance
c.
resistance
d.
specific resistance
specific resistance
The K of a material is defined as the resistance of the wire made from that material which is ? long, and ? in diameter.
Select one:
a.
1 foot / 1 mil
b.
1 meter / 10 mils
c.
100 feet / 1 mil
d.
1,000 feet / 10 mils
1 foot / 1 mil
What happens to the resistance of most conductors as the temperature increases?
Select one:
a.
It decreases.
b.
It increases.
c.
It stays the same (no change).
It increases.
The K factor of a copper conductor at 68°F is ? .
Select one:
a.
1.04
b.
1.76
c.
10.4
d.
17.6
10.4
Match the following cable types to their identifying letters.
I. Armored II. Flat conductor III. Mineral insulated IV. Machine tool wire V. Nonmetallic-sheathed VI. Underground feeder VII. Service entrance cable VIII. Thermoplastic
MTW FCC AC MI NM THW UF SE
iv, ii, i, iii, v, viii, vi, vii
What is the difference between insulation types THW and THWN?
Select one:
a.
THW has a nylon jacket.
b.
THWN has a nylon jacket.
c.
THWN does not have a nylon jacket.
d.
There is no difference in insulation type, only temperature rating.
THWN has a nylon jacket.
Conductors, type SIS, for switchboard wiring, have a maximum operating temperature of ? .
Select one:
a.
90°F
b.
175°F
c.
194°F
d.
212°F
194°F
THW wire is available in sizes from ? to ? .
Select one:
a.
14 AWG / 1,000 kcmil
b.
14 AWG / 2,000 kcmil
c.
18 AWG / 1,000 kcmil
d.
18 AWG / 2,000 kcmil
14 AWG / 2,000 kcmil
Indicate which two of the following cable types are allowed for use in wet locations.
I. RHH II. RHW III. RHW-2 IV. XHH Select one:
a.
I. and II.
b.
I. and III.
c.
I. and IV.
d.
II. and III.
II. and III.
Type XHHW conductors are listed for use in ? location(s).
Select one:
a.
damp
b.
dry
c.
wet
d.
all of the above
all of the above
Listed wire types designated with the suffix ? shall be permitted to be used at a continuous 90°C operating temperature in both wet and dry locations.
Select one:
a.
−2
b.
−9
c.
−90°C
d.
“WD”
−2
The ? of a conductor is defined as the diameter of the conductor in mils, squared.
Select one:
a.
circular-mil area
b.
circumference
c.
mil area
d.
square-mil area
circular-mil area
Match the following inches to their correct conversion in mils.
I. 125 mil II. 250 mils III. 750 mils IV. 1,333 mils V. 4,000 mils VI. 80,000 mils
0.25 inches = mils
0.125 inches = mils
1/4 inch = mils
3/4 inch = mils
ii, i, ii, iii,
a. 0.25inches x 1000 = 250mils
b. 0.125inches × 1,000 = 125 mils
c. convert 1/4 to 0.25inches 0.25 × 1,000 = 250 mils
d. convert 3/4 to 0.75 0.75inches × 1,000 = 750 mils
Match the following mils to their correct conversion in inches.
I. 1/8" II. 3/16" III. 1/4" IV. 5/16" V. 3/8" VI. 1/2" VII. 3/4" 500 mils = inches 375 mils = inches 750 mils = inches 187.5 mils = inches
vi, v, vii, ii
a. 500 mils/1,000 = 0.5” or 1/2”
b. 375 mils/1,000 = 0.375” or 3/8”
c. 750 mils/1,000 = 0.75” or 3/4”
d. 187.5 mils/1,000 = 0.1875” or 3/16”
To find the area of a wire in circular mils, square the diameter expressed in ? .
Select one:
a.
centimeters
b.
feet
c.
inches
d.
mils
mils
Which formula is used to find circular mil area?
Select one:
a.
Acmils = df2
b.
Acmils = dmils2
c.
Acmils = dcmils2
d.
d = Amils2
Acmils = dmils2
Which formula determines the resistance of a conductor?
Select one:
a.
Rohms = K × 2Lfeet / ACM
b.
Rohms = K × Lfeet / Am
c.
Rohms = K × Lfeet / ACM
d.
Rohms = K × Lmeters / ACM
Rohms = K × Lfeet / ACM
What is the resistance of 1,000 feet of No. 14 copper wire? Use given properties.
Given: copper = 10.4 ohms per circular mil foot No. 14 wire circular mil area = 4,110 cmil
Select one:
a.
0.253 Ω
b.
2.53 Ω
c.
25.3 Ω
d.
42.74 Ω
2.53 Ω
R in ohms = K × Length in feet / Area in CM
= 10.4 × 1,000/4,110
= 2.53 Ω
In reference to wire size, AWG stands for American Wire Gauge.
Select one:
True
False
True
Write out in words what 250 kcmil means.
Select one:
a.
two hundred and fifty circular mils
b.
two hundred and fifty thousand circular mils
c.
two hundred and fifty kilo mils
d.
two hundred and fifty million circular mils
two hundred and fifty thousand circular mils
What is the circular mil area of wires having the following diameters?
I. 10.404 II. 100 III. 250 IV. 1,000 V. 10,404 VI. 25,000 VII. 250,000 500 mils = circular mil area 10 mils = circular mil area 0.1020 inch = circular mil area
vii, ii, v
a. 500 × 500 = 250,000 cm or 250 kcmil
b. 10 × 10 = 100 cm
c. 102 × 102 = 10,404 cm or 10.404 kcmil
To find the approximate resistance of a given copper conductor, drop the ? digit from the circular mil area. The result is the number of ? per ohm.
Select one:
a.
first / feet
b.
first / meters
c.
last / feet
d.
last / meters
last / feet
Using the approximate resistance method, what is the resistance of 3,302 feet of 8 AWG copper wire that has a circular mil area of 16,510?
Select one:
a.
0.5 Ω
b.
2 Ω
c.
5 Ω
d.
5,451,602 or 5.5 MΩ
2 Ω
1,651 feet per ohm
3,302/1,651= 2 Ω
What length of 12 AWG copper wire would be required to produce a resistance of five ohms? (Use the approximation method.)
Select one:
a.
0.008 feet
b.
130.6 feet
c.
3,265 feet
d.
32,650 feet
3,265 feet
cm area is 6,530 cm
653 feet per ohm
5 × 653 = 3,265 feet
Match the circular mil area of the following wire sizes.
I. 4,110 cm II. 6,530 cm III. 10,380 cm IV. 16,510 cm V. 26,240 cm VI. 41,740 cm
10 AWG circular mil area 8 AWG circular mil area 6 AWG circular mil area 14 AWG circular mil area 4 AWG circular mil area 12 AWG circular mil area
iii, iv, v, i, vi, ii
In general, all conductors ? AWG and larger, installed in a raceway, shall be stranded.
a. 4
b. 6
c. 8
d. 10
c. 8
310. 3(c)
A person has a piece of wire that has 12 strands, each strand with a diameter of 118.3 mils. To determine the size of wire will require three steps. The first step is to calculate the circular mil area for each strand. What is the circular mil area of each strand? (Round the FINAL answer for this question to the nearest whole number.)
_______ circular mil
13995 CM
CMA = d2 CMA = 118.32 CMA = 13994.89 circular mils CMA = 13995 circular mils
A person has a piece of wire that is 12 strands of 118.3 mils diameter. What is the approximate size of wire? This is the second step in a three step process. You will need this answer for the next question. Second Step: Multiply circular mil area by number of strands.
____ circular mil
167940
13,995 × 12 = 167,940 cmil
A person has a piece of wire that is 12 strands of 118.3 mils diameter. What is the approximate size of wire? This is the third and final step in a three step process. Third Step:
Use Chapter 9, Table 8 of the Code to locate size closest wire size.
The AWG for a wire made up of 12 strands that is 118.3 mils diameter is ? .
Select one:
a.
AWG 18
b.
AWG 8
c.
AWG 1/0
d.
AWG 3/0
e.
250 kcmil
AWG 3/0
How many strands of 10 AWG wire would it take to make a 500-kcmil cable?
Select one:
a.
19
b.
37
c.
49
d.
95
49
The largest size wire listed in wire gauge number is ? .
Select one:
a. #1
b.
4/0
c.
250
d.
2000
4/0
In general, the smallest size conductor permitted for 2,000 V is ? AWG copper or ? AWG aluminum or copper-clad aluminum.
a. 18 / 14
b. 18 / 12
c. 14 / 14
d. 14 / 12
14/12
code: 310.3(A)
Match the conductors to the ampacity that indicates the allowable current-carrying capacity.
Amperes for 3 1/0 AWG, THW, copper in conduit
Amperes for a single 1/0 AWG, THW, copper conductor in free air
Amperes for 3 1/0 AWG, THW, aluminum in conduit
Amperes for a single 1/0 AWG, THW, aluminum conductor in free air
- 150
- 230
- 120
- 180
- 100
150, 230, 120, 180
There are no color coding requirements for grounded conductors found in the NEC.
true or false
false
200.6
What might happen to thermoplastic insulation at temperatures colder than -10°C (+14°F)?
Select one:
a.
This will cause the resistance of the conductor to increase.
b.
The insulation might stiffen.
c.
The insulation will crack.
d.
Nothing. Thermoplastic insulation is designed to stay flexible down to -25°C.
The insulation might stiffen.
The allowable ampacities in Table 310.16 and Table 310.17 are based on an ambient temperature of ? .
Select one:
a.
75°F
b.
86°F
c.
90°F
d.
100°F
86°F
