WorksheetsL109 Electrical Wiring and Cable Ampacity Worksheet
Total questions: 50
Worksheet time: 25mins
A THHN copper conductor has a maximum operating temperature of:
60 °C
75 °C
90 °C
105 °C
A #10 AWG copper THWN-2 conductor connected to 60 °C-rated terminals must be sized using which ampacity value:
20 A
25 A
30 A
40 A
Nonmetallic-sheathed cable (NM-B) is approved for use in which location:
Damp industrial bay
Concealed residential walls
In outdoor cable trays
Embedded in concrete slabs
NM cable bored through framing must be at least how far from the wood edge:
1/2 in
1 in
1 1/4 in
2 in
A 12 AWG copper NM-B protected by a 20 A breaker has an ampacity (60 °C column) of:
15 A
20 A
25 A
30 A
Type NM cable must be secured within how many inches of a nonmetallic box:
8
12
18
24
A #8 AWG copper THHN conductor in the 90 °C column has an ampacity of:
40 A
50 A
55 A
60 A
In a 120/240 V single-phase system, which conductors share a neutral:
Two hots 180° apart
Two hots 120° apart
Two hots same phase
Any two hots
NM cable cannot be exposed where subject to damage unless:
Stapled every 4.5 ft
Protected by conduit or guard strips
Sunlight resistant
THWN rated
For a 30 A branch circuit using NM cable, the minimum conductor size is:
#14
#12
#10
#8
One of the colors typically used for a 277 V circuit conductor is:
Black
Red
Orange
Blue
The maximum number of 12 AWG conductors allowed in a 4 in square, 2 1/8 in deep box (no devices) is:
15
12
13
9
When derating conductors, adjustments start with which ampacity column if insulation is 90 °C:
60 °C
75 °C
90 °C
Ambient
Type NM cable must be supported at intervals not exceeding:
2 ft
4.5 ft
6 ft
8 ft
A 14 AWG Cu NM-B cable has what ampacity at 60 °C:
15 A
20 A
25 A
30 A
A 120 V circuit draws 12 A continuous. The minimum OCPD size if using 125% rule is:
15 A
20 A
25 A
30 A
The NEC requires NM cable to be protected by nail plates if closer than ___ to edge of framing:
1/2 in
1 in
1 1/4 in
2 in
A #6 AWG copper THWN-2 conductor ampacity at 75 °C is:
55 A
65 A
75 A
95 A
A 3-wire single-phase system with black, red, white is typically:
120/208 V
120/240 V
277/480 V
480 V delta
Which conductor color is required for the grounded neutral in NM cable:
White or gray
Green
Black
Red
A 15 Amp general lighting circuit in a dwelling typically uses which conductor size:
#14
#12
#10
#8
When more than 2 NM cables are bundled for more than 24 in, what must be applied:
Nothing
Use 60 °C rating
Ampacity adjustment
Increase breaker
The ampacity of a #4 Cu THHN at 90 °C is:
70 A
85 A
95 A
115 A
NM-B cable is rated for what maximum conductor temperature:
60 °C
75 °C
90 °C
105 °C
In a single-gang plastic box, what is the volume allowances for one 12 AWG conductor:
1 in3
1.5 in3
2 in3
2.25 in3
What is the maximum allowed fill percentage for a conduit with more than 2 conductors:
30%
40%
53%
60%
NM cable must be fastened within how many inches of a panelboard:
8
12
18
24
A #3 Cu THHN in the 75 °C column has an ampacity of:
85 A
100 A
110 A
115 A
In a 277/480 V system, what color is typically NOT used for the 277 V phase:
Brown
Orange
Yellow
Blue
A #2 AWG Cu THWN-2 has an ampacity at 90 °C of:
95 A
110 A
130 A
150 A
Nonmetallic-sheathed cable cannot be used in which location:
Residential basements
Commercial garages
Residential attics
Residential wood stud walls
A 4 in octagon box with 1 device and 6 #12 conductors needs how much total volume allowances:
13.5 in3
15.75 in3
20.25 in3
18 in3
The minimum bending radius of NM cable is:
4x cable diameter
5x cable diameter
6x cable diameter
8x cable diameter
A #1 AWG Cu THHN ampacity at 75 °C is:
110 A
130 A
150 A
170 A
For a multiwire branch circuit, the disconnecting means must simultaneously disconnect:
Hot only
Neutral only
Both ungrounded conductors
All conductors including ground
Which voltage system uses black, red, orange for phases and white for neutral:
120/208 V 3φ
277/480 V 3φ
120/240 V 1φ
480 V delta
NM cable must be protected when passing through metal studs by:
Listed plastic bushings and Grommets
No Protection required
Listed protection plates
Electrical tape
When a Type NM cable passes through a hole in a wood stud where the edge of the hole is less than 1¼ inches from the face of the stud, what protection must be provided?
Listed plastic bushings and Grommets
No Protection required
Listed protection plates
Electrical tape
In a 120/208 V panel, what color is used for the high leg (if present):
Orange
Yellow
Brown
Gray
The grounded conductor in a wiring system must have an outer finish that is which of the following colors?
Green or bare
White or gray
Red or blue
Black or orange
Metal boxes must be bonded to:
Neutral
Grounding conductor
Hot leg
Conduit
A #6 AL THWN-2 conductor ampacity at 75 °C is:
40 A
50 A
55 A
65 A
The maximum fill percentage for one conductor in conduit is:
40%
53%
60%
70%
The NEC requires securing NM cable within how many feet between supports:
4.5 ft
6 ft
8 ft
12 ft
A #3/0 Cu THHN in 75 °C column has an ampacity of:
165 A
175 A
200 A
225 A
When applying ambient temperature correction to 90 °C THHN, you start with:
60 °C column
75 °C column
90 °C column
Any column
What is the ampacity of a #4 AWG copper THHN conductor at 75 °C?
70 A
100 A
95 A
85 A
Which of the following must be bonded to the grounding conductor in a metal junction box installation?
All conductors
Only the neutral conductor
Only the hot conductor
The box itself
For a 20 A branch circuit using NM cable, what is the minimum required conductor size?
#14 AWG
#12 AWG
#8 AWG
#10 AWG
According to the NEC, what is a small appliance branch circuit?
A 15- or 20-amp branch circuit that supplies lighting outlets only
A 15- or 20-amp branch circuit that supplies only bathroom receptacles
A 20-amp branch circuit that supplies receptacle outlets in kitchens, breakfast rooms, dining rooms, and similar areas
A 30-amp branch circuit that supplies fixed cooking equipment
