Theory Units 27-29

Question 1

The cross-sectional area of a wire is commonly expressed in _____.
Answer 1: square inches
Answer 2: mils
Answer 3: circular mils
Answer 4: none of these

Answer 1

circular mils

Question 2

In dc circuits, the only property that affects current flow is _____.
Answer 1: impedance
Answer 2: reactance
Answer 3: resistance
Answer 4: none of these

Answer 2

resistance

Question 3

Wire dc resistance is determined by the _____.
Answer 1: material type
Answer 2: cross-sectional area
Answer 3: wire length and operating temperature
Answer 4: all of these

Answer 3

all of these

Question 4

Smaller wires have _____ resistance and larger wires have lower resistance.

Answer 1: lesser
Answer 2: greater
Answer 3: the same
Answer 4: all of these

Answer 4

greater

Question 5

The resistance of a wire is affected by temperature change. This is called the _____.

Answer 1: temperature correction factor
Answer 2: temperature coefficient
Answer 3: ambient temperature factor
Answer 4: none of these

Answer 5

temperature coefficient

Question 6

The _____ lists the resistance and area in circular mils for both direct-current and alternating-current circuit wires.

Answer 1: NEC
Answer 2: CEC
Answer 3: IEC
Answer 4: none of these

Answer 6

NEC

Question 7

What is the direct-current resistance of a 1 AWG copper wire that is 200 ft long?

Answer 1: 0.0308
Answer 2: 0.0311
Answer 3: 0.0423
Answer 4: 0.0564

Answer 7

0.0308

Question 8

What is the direct-current resistance of a 3 AWG aluminum wire that is 1,000 ft long?

Answer 1: 0.231
Answer 2: 0.313
Answer 3: 0.403
Answer 4: 0.422

Answer 8

0.403

Question 9

What is the direct-current resistance of a 1/0 AWG aluminum wire that is 800 ft long?

Answer 1: 0.08
Answer 2: 0.16
Answer 3: 0.23
Answer 4: 0.56

Answer 9

0.16

Question 10

What is the direct-current resistance of a 1 AWG copper wire that is 100 ft long?

Answer 1: 0.0154
Answer 2: 0.1620
Answer 3: 0.2330
Answer 4: 0.5610

Answer 10

0.0154

Question 11

What is the direct-current resistance of a 3 AWG aluminum wire that is 500 ft long?

Answer 1: 0.0231
Answer 2: 0.1614
Answer 3: 0.2015
Answer 4: 0.2330

Answer 11

0.2015

Question 12

According to Chapter 9, Table 8 in the textbook, what is the cross-sectional area in circular mils for a 12 AWG wire?

Answer 1: 4,740 cmil
Answer 2: 6,536 cmil
Answer 3: 7,380 cmil
Answer 4: 8,690 cmil

Answer 12

6,536 cmil

Question 13

According to Chapter 9, Table 8 in the textbook, what is the cross-sectional area in circular mils for a 10 AWG wire?

Answer 1: 7,740 cmil
Answer 2: 8,360 cmil
Answer 3: 9,380 cmil
Answer 4: 10,380 cmil

Answer 13

10,380 cmil

Question 14

According to Chapter 9, Table 8 in the textbook, what is the cross-sectional area in circular mils for an 8 AWG wire?

Answer 1: 13,690 cmil
Answer 2: 16,510 cmil
Answer 3: 17,800 cmil
Answer 4: 18,600 cmil

Answer 14

16,510 cmil

Question 15

For ac circuits, the ac _____ of a wire is greater than the dc resistance because of eddy currents and skin effect.

Answer 1: voltage
Answer 2: current
Answer 3: resistance
Answer 4: power

Answer 15

resistance

Question 16

The opposition to current flow is greater for alternating-current circuits than for direct-current circuits because of _____.

Answer 1: eddy currents
Answer 2: skin effect
Answer 3: eddy currents and skin effect
Answer 4: none of these

Answer 16

eddy currents and skin effect

Question 17

A _____ wire results in greater wire resistance and greater wire voltage drop.

Answer 1: wider
Answer 2: shorter
Answer 3: longer
Answer 4: none of these

Answer 17

longer

Question 18

What is the operating voltage of a single-phase, 12A, 230V rated load wired with 10 AWG if it is located 250 ft from the power supply, and has a nominal circuit voltage of 240V?

Answer 1: 200.40V
Answer 2: 216.60V
Answer 3: 232.56V
Answer 4: 238.80V

Answer 18

232.56V

Question 19

What is the voltage drop of two 12 AWG wires supplying a 12A continuous load located 100 ft from the power supply?

Answer 1: 3.20V to 3.25V
Answer 2: 4.40V to 4.50V
Answer 3: 4.75V to 4.80V
Answer 4: 5.80V to 6.00V

Answer 19

4.75V to 4.80V

Question 20

A 240V, 20A, single-phase load is located 100 ft from the panelboard and is wired with 10 AWG wires. What is the voltage drop of the circuit wires?

Answer 1: 3V
Answer 2: 4V
Answer 3: 5V
Answer 4: 6V

Answer 20

5V

Question 21

What is the operating voltage of a single-phase, 24A, 230V rated load wired with 10 AWG if it is located 200 ft from the power supply, and has a nominal circuit voltage of 240V?

Answer 1: 228.48V
Answer 2: 229.80V
Answer 3: 230.30V
Answer 4: 231.80V

Answer 21

228.48V

Question 22

The common point of a 4-wire, three-phase, wye-connected system; the midpoint of a 3-wire, single-phase system; or the midpoint of the single-phase portion of a three-phase, delta-connected system is referred to as the _____ point.

Answer 1: neutral
Answer 2: phase
Answer 3: copper
Answer 4: none of these

Answer 22

neutral

Question 23

The grounded wire is a wire that is intentionally _____ to the Earth.

Answer 1: grounded
Answer 2: bolted
Answer 3: earthed
Answer 4: bonded

Answer 23

grounded

Question 24

The current on the neutral wire is equal to the difference in phase wire current because at any instant the currents on the two phase wires _____ each other.

Answer 1: attract
Answer 2: oppose
Answer 3: equal
Answer 4: rely

Answer 24

oppose

Question 25

Multiwire branch circuits are more _____ than 2-wire circuits in that they have fewer wires for a given number of circuits, which enables the use of a smaller raceway, and result in lower circuit voltage drop. Answer 1: cost effective Answer 2: conductive Answer 3: nicer Answer 4: easier

Answer 25

cost effective

Question 26

Multiwire branch circuits have _____ wires for a given number of circuits, which requires the use of a smaller raceway. Answer 1: fewer Answer 2: more Answer 3: bigger Answer 4: smaller

Answer 26

fewer

Question 27

If the number of wires is reduced for a multiwire circuit, the size of the raceway can often be _____. Answer 1: reduced Answer 2: copper Answer 3: increased Answer 4: aluminum

Answer 27

reduced

Question 28

A typical 2-wire circuit has current flow over both the phase and neutral wires and the circuit voltage drop includes the voltage drop of _____ wire(s). Answer 1: zero Answer 2: one Answer 3: both Answer 4: three

Answer 28

both

Question 29

What is the voltage drop of two 12 AWG wires, each 150 ft long, supplying a 2-wire, 20A load? Answer 1: 6V Answer 2: 10V Answer 3: 12V Answer 4: 16V

Answer 29

12V

Question 30

A balanced 3-wire, single-phase or 4-wire, three-phase multiwire branch circuit has current flowing only on the phase circuit wires and the circuit voltage drop includes the voltage drop of _____ wire(s). Answer 1: one Answer 2: two Answer 3: three Answer 4: four

Answer 30

one

Question 31

What is the circuit voltage drop over each line wire of a balanced 3-wire multiwire circuit? Each wire is 12 AWG, 150 ft long, supplying a 20A load. Answer 1: 2V Answer 2: 3V Answer 3: 4V Answer 4: 6Vselected

Answer 31

6V

Question 32

Improper wiring or mishandling of multiwire circuits can cause _____. Answer 1: better power quality Answer 2: a fire hazard Answer 3: equipment failure Answer 4: a fire hazard and/or equipment failure

Answer 32

a fire hazard and/or equipment failure

Question 33

If the continuity of the _____ wire of a multiwire circuit is interrupted (opened), there could be a fire and/or destruction of electrical equipment resulting from overvoltage or undervoltage. Answer 1: grounding Answer 2: neutral Answer 3: phase Answer 4: all of these

Answer 33

neutral

Question 34

What is the resistance of the circuit wires when the wire voltage drop is 7.20V and the current flow is 50A? Answer 1: 0.14 Answer 2: 0.30 Answer 3: 3 Answer 4: 14

Answer 34

0.14

Question 35

What is the resistance of the circuit wires when the wire voltage drop is 3.60V and the current flow is 20A? Answer 1: 0.15 Answer 2: 0.18 Answer 3: 3.0 Answer 4: 5.55

Answer 35

0.18

Question 36

What is the resistance of the circuit wires when the wire voltage drop is 14.40V and the current flow is 60A? Answer 1: 0.24 Answer 2: 0.30 Answer 3: 3.14 Answer 4: 4.20

Answer 36

0.24

Question 37

What is the current flow in amperes through a 9.50 kW heat strip rated 230V when connected to a 230V power source? Answer 1: 25A Answer 2: 39A Answer 3: 41A Answer 4: 230A

Answer 37

41A

Question 38

What is the current flow in amperes through a 9.50 kW heat strip rated 208V when connected to a 208V power source? Answer 1: 35A Answer 2: 39A Answer 3: 46A Answer 4: 55A

Answer 38

46A

Question 39

What is the current flow in amperes through a 6.50 kW heat strip rated 480V when connected to a 480V power source? Answer 1: 13.50A Answer 2: 19.40A Answer 3: 21.30A Answer 4: 23.20A

Answer 39

13.50A

Question 40

What is the voltage of a circuit carrying 4.80A supplying a 100Ω resistor? Answer 1: 110V Answer 2: 220V Answer 3: 360V Answer 4: 480V

Answer 40

480V

Question 41

What is the voltage of a circuit carrying 20.80A supplying a 10Ω resistor? Answer 1: 110V Answer 2: 208V Answer 3: 460V Answer 4: 500V

Answer 41

208V

Question 42

What is the voltage of a circuit carrying 4.60A supplying a 52Ω resistor? Answer 1: 110V Answer 2: 120V Answer 3: 230V Answer 4: 240V

Answer 42

240V

Question 43

What is the power loss at a terminal having a resistance of 0.20Ω when carrying 40A? Answer 1: 100W Answer 2: 210W Answer 3: 320W Answer 4: 430W

Answer 43

320W

Question 44

What is the power loss at a terminal having a resistance of 0.50Ω when carrying 15A? Answer 1: 112.50W Answer 2: 200.40W Answer 3: 230.20W Answer 4: 340.30W

Answer 44

112.50W

Question 45

What is the power loss at a terminal having a resistance of 0.70Ω when carrying 10A? Answer 1: 10W Answer 2: 40W Answer 3: 70W Answer 4: 100W

Answer 45

70W