Illinois Master Electrician Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. Which of the following is the primary purpose of a grounding
conductor?
A. To carry normal operating current
B. To provide a path for fault current
C. To increase voltage
D. To act as a neutral conductor
Rationale: A grounding conductor provides a low-resistance path to
safely carry fault current to the earth, preventing electric shock and
equipment damage.
2. According to the NEC, what is the maximum number of 12 AWG
conductors allowed in a standard 20-ampere residential circuit?
A. 10
B. 12
C. 12
D. 14
Rationale: NEC 310.15(B)(16) allows up to 12 current-carrying
conductors in a 20A circuit without adjustment factors for heat.
3. What is the minimum height above finished grade for service entrance
conductors over a residential driveway?
A. 10 feet
B. 12 feet
C. 12 feet
D. 14 feet
, Rationale: NEC 230.24 requires a minimum of 12 feet clearance over
residential driveways for safety.
4. What is the purpose of an AFCI (Arc-Fault Circuit Interrupter)?
A. Protect against short circuits
B. Protect against overloads
C. Protect against arcing faults
D. Reduce voltage drop
Rationale: AFCIs detect arcing conditions that could cause fires and
shut off the circuit.
5. Which type of conduit is typically required for wet locations?
A. EMT
B. RMC (Rigid Metal Conduit)
C. FMC
D. PVC without rating
Rationale: RMC provides full protection against moisture and
physical damage in wet locations.
6. In a 3-phase 4-wire system, the neutral carries:
A. No current
B. Only harmonic currents
C. Only fault currents
D. The unbalanced current
Rationale: The neutral in a 3-phase system carries the difference of
the phase currents when the loads are unbalanced.
7. What is the maximum allowable voltage drop for feeders according to
best practice recommendations?
A. 2%
B. 3%
C. 3%
D. 5%
Rationale: To maintain voltage quality, the NEC recommends a
maximum of 3% voltage drop for feeders.
8. Which type of insulation is rated for 600 volts?
A. TW
B. THHN
C. UF
, D. NM-B
Rationale: THHN insulation is rated for 600V in dry locations and
suitable for conduit installations.
9. What is the minimum required ampacity for a 100-amp service using
copper conductors?
A. 1 AWG
B. 3 AWG
C. 2 AWG
D. 4 AWG
Rationale: NEC 310.15(B)(16) specifies 3 AWG copper conductors
have 100A ampacity at 75°C rating.
10. Which of the following is required for GFCI protection in a
kitchen?
A. Only the refrigerator
B. Only the dishwasher
C. All countertop receptacles
D. Only lighting circuits
Rationale: NEC 210.8(A) requires GFCI protection for all kitchen
countertop receptacles to prevent shock hazards.
11. What is the primary function of a main bonding jumper in a
service?
A. To carry normal load current
B. To connect the service neutral to the grounding electrode system
C. To increase voltage
D. To protect against arcing
Rationale: The main bonding jumper ensures the neutral is bonded to
ground at the service to maintain a reference point and facilitate
proper fault clearing.
12. Which NEC article covers wiring methods?
A. 210
B. 220
C. 300
D. 310
Rationale: NEC Article 300 covers wiring methods, including conduit,
cables, and cable trays.
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. Which of the following is the primary purpose of a grounding
conductor?
A. To carry normal operating current
B. To provide a path for fault current
C. To increase voltage
D. To act as a neutral conductor
Rationale: A grounding conductor provides a low-resistance path to
safely carry fault current to the earth, preventing electric shock and
equipment damage.
2. According to the NEC, what is the maximum number of 12 AWG
conductors allowed in a standard 20-ampere residential circuit?
A. 10
B. 12
C. 12
D. 14
Rationale: NEC 310.15(B)(16) allows up to 12 current-carrying
conductors in a 20A circuit without adjustment factors for heat.
3. What is the minimum height above finished grade for service entrance
conductors over a residential driveway?
A. 10 feet
B. 12 feet
C. 12 feet
D. 14 feet
, Rationale: NEC 230.24 requires a minimum of 12 feet clearance over
residential driveways for safety.
4. What is the purpose of an AFCI (Arc-Fault Circuit Interrupter)?
A. Protect against short circuits
B. Protect against overloads
C. Protect against arcing faults
D. Reduce voltage drop
Rationale: AFCIs detect arcing conditions that could cause fires and
shut off the circuit.
5. Which type of conduit is typically required for wet locations?
A. EMT
B. RMC (Rigid Metal Conduit)
C. FMC
D. PVC without rating
Rationale: RMC provides full protection against moisture and
physical damage in wet locations.
6. In a 3-phase 4-wire system, the neutral carries:
A. No current
B. Only harmonic currents
C. Only fault currents
D. The unbalanced current
Rationale: The neutral in a 3-phase system carries the difference of
the phase currents when the loads are unbalanced.
7. What is the maximum allowable voltage drop for feeders according to
best practice recommendations?
A. 2%
B. 3%
C. 3%
D. 5%
Rationale: To maintain voltage quality, the NEC recommends a
maximum of 3% voltage drop for feeders.
8. Which type of insulation is rated for 600 volts?
A. TW
B. THHN
C. UF
, D. NM-B
Rationale: THHN insulation is rated for 600V in dry locations and
suitable for conduit installations.
9. What is the minimum required ampacity for a 100-amp service using
copper conductors?
A. 1 AWG
B. 3 AWG
C. 2 AWG
D. 4 AWG
Rationale: NEC 310.15(B)(16) specifies 3 AWG copper conductors
have 100A ampacity at 75°C rating.
10. Which of the following is required for GFCI protection in a
kitchen?
A. Only the refrigerator
B. Only the dishwasher
C. All countertop receptacles
D. Only lighting circuits
Rationale: NEC 210.8(A) requires GFCI protection for all kitchen
countertop receptacles to prevent shock hazards.
11. What is the primary function of a main bonding jumper in a
service?
A. To carry normal load current
B. To connect the service neutral to the grounding electrode system
C. To increase voltage
D. To protect against arcing
Rationale: The main bonding jumper ensures the neutral is bonded to
ground at the service to maintain a reference point and facilitate
proper fault clearing.
12. Which NEC article covers wiring methods?
A. 210
B. 220
C. 300
D. 310
Rationale: NEC Article 300 covers wiring methods, including conduit,
cables, and cable trays.
