Illinois Electrical Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the minimum wire size allowed for a 20-ampere branch circuit
supplying general lighting in a dwelling?
A. 14 AWG
B. 12 AWG
C. 10 AWG
D. 8 AWG
Rationale: 12 AWG copper wire is the minimum size for a 20-ampere
general lighting branch circuit according to the National Electrical
Code (NEC).
2. What is the standard residential voltage for most household
appliances in Illinois?
A. 120 V
B. 208 V
C. 120/240 V
D. 277 V
Rationale: Most residential homes use 120/240 volts single-phase
service for standard appliances and outlets.
3. According to the NEC, how many disconnecting means are required for
a single-family dwelling service?
A. None
B. One
C. Two
D. Three
, Rationale: A single-family dwelling requires at least one main
disconnecting means to shut off all power to the building safely.
4. Ground-fault circuit interrupters (GFCIs) are required in which areas of
a dwelling?
A. Bedrooms only
B. Bathrooms, kitchens, garages, and outdoor outlets
C. Living rooms
D. Attics
Rationale: NEC requires GFCIs in locations with increased risk of
electric shock, such as bathrooms, kitchens, garages, and outdoor
outlets.
5. What is the purpose of an arc-fault circuit interrupter (AFCI)?
A. Reduce voltage
B. Prevent fires caused by arcing faults
C. Protect from ground faults
D. Increase current
Rationale: AFCIs detect arcing conditions in wiring and prevent fires
caused by electrical arcs.
6. The maximum number of 12 AWG conductors allowed in a 3/4-inch
EMT conduit is:
A. 4
B. 5
C. 6
D. 7
Rationale: According to NEC conduit fill tables, 6 conductors of 12
AWG can fit safely in a 3/4-inch EMT.
7. Which type of grounding electrode is required for a residential
service?
A. Water pipe only
B. Metal underground water pipe, concrete-encased electrode, or
ground rod
C. Plastic pipe
D. None
Rationale: NEC specifies acceptable grounding electrodes such as
metal water pipes, concrete-encased electrodes, or ground rods.
, 8. What color is typically used for a grounded (neutral) conductor?
A. Black
B. Red
C. White
D. Green
Rationale: White or gray insulation is designated for grounded
(neutral) conductors in residential wiring.
9. Which device is used to protect a branch circuit from overcurrent?
A. Transformer
B. Circuit breaker or fuse
C. Switch
D. GFCI
Rationale: Circuit breakers or fuses interrupt current flow when a
circuit is overloaded or short-circuited.
10. How far above the floor must receptacles be installed in a
kitchen per NEC?
A. 12 inches
B. 15 inches
C. Not more than 48 inches above the countertop
D. 60 inches
Rationale: NEC specifies receptacles above countertops should not
exceed 48 inches for accessibility.
11. In a 240 V single-phase circuit, what is the phase-to-phase
voltage?
A. 120 V
B. 240 V
C. 208 V
D. 480 V
Rationale: Single-phase 240 V circuits have 240 volts across the two
hot conductors.
12. Which conductor is used for equipment grounding?
A. Black
B. Red
C. Green or bare copper
D. White
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the minimum wire size allowed for a 20-ampere branch circuit
supplying general lighting in a dwelling?
A. 14 AWG
B. 12 AWG
C. 10 AWG
D. 8 AWG
Rationale: 12 AWG copper wire is the minimum size for a 20-ampere
general lighting branch circuit according to the National Electrical
Code (NEC).
2. What is the standard residential voltage for most household
appliances in Illinois?
A. 120 V
B. 208 V
C. 120/240 V
D. 277 V
Rationale: Most residential homes use 120/240 volts single-phase
service for standard appliances and outlets.
3. According to the NEC, how many disconnecting means are required for
a single-family dwelling service?
A. None
B. One
C. Two
D. Three
, Rationale: A single-family dwelling requires at least one main
disconnecting means to shut off all power to the building safely.
4. Ground-fault circuit interrupters (GFCIs) are required in which areas of
a dwelling?
A. Bedrooms only
B. Bathrooms, kitchens, garages, and outdoor outlets
C. Living rooms
D. Attics
Rationale: NEC requires GFCIs in locations with increased risk of
electric shock, such as bathrooms, kitchens, garages, and outdoor
outlets.
5. What is the purpose of an arc-fault circuit interrupter (AFCI)?
A. Reduce voltage
B. Prevent fires caused by arcing faults
C. Protect from ground faults
D. Increase current
Rationale: AFCIs detect arcing conditions in wiring and prevent fires
caused by electrical arcs.
6. The maximum number of 12 AWG conductors allowed in a 3/4-inch
EMT conduit is:
A. 4
B. 5
C. 6
D. 7
Rationale: According to NEC conduit fill tables, 6 conductors of 12
AWG can fit safely in a 3/4-inch EMT.
7. Which type of grounding electrode is required for a residential
service?
A. Water pipe only
B. Metal underground water pipe, concrete-encased electrode, or
ground rod
C. Plastic pipe
D. None
Rationale: NEC specifies acceptable grounding electrodes such as
metal water pipes, concrete-encased electrodes, or ground rods.
, 8. What color is typically used for a grounded (neutral) conductor?
A. Black
B. Red
C. White
D. Green
Rationale: White or gray insulation is designated for grounded
(neutral) conductors in residential wiring.
9. Which device is used to protect a branch circuit from overcurrent?
A. Transformer
B. Circuit breaker or fuse
C. Switch
D. GFCI
Rationale: Circuit breakers or fuses interrupt current flow when a
circuit is overloaded or short-circuited.
10. How far above the floor must receptacles be installed in a
kitchen per NEC?
A. 12 inches
B. 15 inches
C. Not more than 48 inches above the countertop
D. 60 inches
Rationale: NEC specifies receptacles above countertops should not
exceed 48 inches for accessibility.
11. In a 240 V single-phase circuit, what is the phase-to-phase
voltage?
A. 120 V
B. 240 V
C. 208 V
D. 480 V
Rationale: Single-phase 240 V circuits have 240 volts across the two
hot conductors.
12. Which conductor is used for equipment grounding?
A. Black
B. Red
C. Green or bare copper
D. White
