Theory Units 27-29 Flashcards
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
circular mils
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
resistance
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
all of these
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
greater
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
temperature coefficient
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
NEC
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
0.0308
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
0.403
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
0.16
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
0.0154
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
0.2015
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
6,536 cmil
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
10,380 cmil
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
16,510 cmil
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
resistance
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
eddy currents and skin effect
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
longer
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
232.56V
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
4.75V to 4.80V
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
5V
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
228.48V
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
neutral
The grounded wire is a wire that is intentionally _____ to the Earth.
Answer 1: grounded
Answer 2: bolted
Answer 3: earthed
Answer 4: bonded
grounded
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
oppose
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
cost effective
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
fewer
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
reduced
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
both
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
12V
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
one
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
6V
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
a fire hazard and/or equipment failure
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
neutral
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
0.14
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
0.18
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
0.24
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
41A
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
46A
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
13.50A
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
480V
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
208V
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
240V
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
320W
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
112.50W
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
70W
