Deck 6: Using Wire Tables and Determining Conductor Sizes

Question 1

Describe the information in NEC Table 310.104(A), which specifies types of insulation.

Answer 1

The table is divided into seven main columns. The first column lists the trade name of the insulation; the second lists its identification code letter; the third column lists its maximum operating temperature; and the fourth shows its applications and where it is permitted to be used. The fifth column lists the material from which the insulation is made; the sixth states its thickness; and the last column lists the type of outer covering over the insulation.

Question 2

If conductors are to be used in a location with a higher ambient temperature, the ampacity of the conductor must be ____.

A) kept constant
B) doubled
C) reduced
D) increased by 20 amperes

Answer 2

C

Question 3

What is the maximum operating temperature (in degrees Celsius) for Type SIS insulation?

A) 60
B) 90
C) 200
D) 250

Answer 3

B

Question 4

An aluminum wire 2250 feet long cannot have a resistance greater than 0.2 ohm. What is the minimum size wire (in circular mils) that may be used?

Question 5

According to the NEC, what five conditions must be met when conductors are in parallel?

Question 6

After the conductors have been installed in conduits or raceways, it is accepted practice to test the installation for grounds and shorts. This test requires a(n) .

A) faradmeter
B) ammeter
C) voltmeter
D) ohmmeter

Question 7

Twelve 14 AWG copper conductors with type RHW insulation are to be installed in conduit in an area with an ambient temperature of 110 degrees F (43 degrees C). What will be the ampacity of these conductors?

A) 4.1 amperes
B) 8.2 amperes
C) 16.4 amperes
D) 32.8 amperes

Question 8

If you have a raceway with 35 current-carrying conductors, by what adjustment factor must you multiply the ampacity?

A) 0.2
B) 0.3
C) 0.4
D) 0.5

Question 9

Find the resistance of 6 AWG copper wire 550 feet long. Assume a temperature of 20 degrees Celsius.

A) 0.00201 ohm
B) 0.159 ohm
C) 0.218 ohm
D) 4.59 ohm

Question 10

loss is caused by the continuous aligning and realigning of molecules, which produces heat due to friction.

A) Insulation
B) Hysteresis
C) Short
D) Ground

Question 11

The conductors of a single phase are not permitted to be run in metallic conduit because currents will be induced.

A) eddy
B) series
C) parallel
D) superconducting

Question 12

Currents of a three-phase system are degrees out of phase with each other.

A) 60
B) 90
C) 120
D) 180

Question 13

How do wire material and diameter affect resistance?

Question 14

How are wire installations tested for shorts and grounds?

Question 15

The formula for calculating resistance of a certain length, size, and type of wire is: R = .

A) (K × L)/cmil
B) K/(L × cmil)
C) L/(K × cmil)
D) L × (cmil/K)

Question 16

If the ambient temperature is above degrees Celsius, a correction factor must be applied to allowable ampacities for conductors.

A) 15
B) 20
C) 25
D) 30

Question 17

The listed ampacities in the Code tables assume that the length of the conductor will not significantly increase the of the circuit.

A) ampacity
B) resistance
C) capacitance
D) inductance

Question 18

A factor that determines the amount of current a conductor is permitted to carry is the type of used, which is the nonconductive covering around the wire.

A) insulation
B) raceway
C) busway
D) voltage

Question 19

Materials that increase their resistance with an increase of temperature have a coefficient of temperature.

A) decimal
B) constant
C) positive
D) negative

Question 20

A conductor made out of what material is allowed to carry the most current, assuming that size and insulation type are held constant?

A) copper-clad aluminum
B) silicone
C) aluminum
D) copper