CO Journeyman Electrician Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the maximum overcurrent protection allowed for a 14 AWG
copper conductor in a general-purpose branch circuit?
A. 10 amps
B. 15 amps
C. 20 amps
D. 25 amps
Rationale: According to the NEC, 14 AWG copper conductors are
rated for 15 amps maximum in general-use branch circuits.
2. Which device is used to protect against ground faults?
A. Circuit breaker
B. Fuse
C. GFCI (Ground Fault Circuit Interrupter)
D. AFCI (Arc Fault Circuit Interrupter)
Rationale: GFCIs are designed to detect ground faults and interrupt
the circuit to prevent electric shock.
3. What is the color code for a grounded conductor in residential wiring?
A. Black
B. Red
C. White
D. Green
Rationale: The NEC requires that grounded (neutral) conductors be
white or gray.
4. What is the typical voltage of a single-phase residential service?
A. 120V only
, B. 208V
C. 120/240V
D. 277V
Rationale: Standard U.S. residential services provide 120/240V
single-phase voltage.
5. A 20-ampere circuit breaker should be used with which minimum
conductor size?
A. 14 AWG
B. 12 AWG
C. 10 AWG
D. 8 AWG
Rationale: NEC Table 310.15 specifies that 12 AWG copper wire is
suitable for 20 amps.
6. The maximum number of 14 AWG conductors allowed in a 20-ampere
junction box is:
A. 2
B. 3
C. 4
D. 5
Rationale: NEC box fill calculations allow 5 current-carrying 14
AWG conductors in a standard single-gang box.
7. What type of conduit is non-metallic and often used in residential wet
locations?
A. EMT
B. RMC
C. PVC
D. IMC
Rationale: PVC conduit is non-metallic, corrosion-resistant, and
suitable for wet locations.
8. Which tool is used to measure insulation resistance?
A. Multimeter
B. Clamp meter
C. Megger
D. Voltmeter
Rationale: A megohmmeter (megger) is specifically designed to test
insulation resistance.
, 9. What is the NEC standard for arc-fault circuit interrupters in
bedrooms?
A. Optional
B. Required
C. Not allowed
D. Only in commercial buildings
Rationale: NEC 210.12 requires AFCIs in all bedroom circuits to
protect against arc faults.
10. The primary purpose of a bonding conductor is to:
A. Carry normal current
B. Ensure a low-resistance path to ground
C. Reduce voltage drop
D. Protect against overcurrent
Rationale: Bonding ensures all metal parts are at the same potential,
reducing shock risk.
11. Which type of grounding electrode is required for a residential
service?
A. Copper rod only
B. Concrete-encased electrode only
C. Any approved electrode like rod, pipe, or plate
D. None required
Rationale: NEC allows several types of approved grounding
electrodes for residential service.
12. Which device protects equipment from overcurrent but not from
ground faults?
A. Circuit breaker
B. GFCI
C. AFCI
D. Surge protector
Rationale: Circuit breakers protect conductors and equipment from
overcurrent but not ground faults.
13. In a 3-phase 4-wire system, the phase-to-phase voltage is 208V.
The phase-to-neutral voltage is:
A. 120V
B. 208V
C. 120V
D. 240V
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the maximum overcurrent protection allowed for a 14 AWG
copper conductor in a general-purpose branch circuit?
A. 10 amps
B. 15 amps
C. 20 amps
D. 25 amps
Rationale: According to the NEC, 14 AWG copper conductors are
rated for 15 amps maximum in general-use branch circuits.
2. Which device is used to protect against ground faults?
A. Circuit breaker
B. Fuse
C. GFCI (Ground Fault Circuit Interrupter)
D. AFCI (Arc Fault Circuit Interrupter)
Rationale: GFCIs are designed to detect ground faults and interrupt
the circuit to prevent electric shock.
3. What is the color code for a grounded conductor in residential wiring?
A. Black
B. Red
C. White
D. Green
Rationale: The NEC requires that grounded (neutral) conductors be
white or gray.
4. What is the typical voltage of a single-phase residential service?
A. 120V only
, B. 208V
C. 120/240V
D. 277V
Rationale: Standard U.S. residential services provide 120/240V
single-phase voltage.
5. A 20-ampere circuit breaker should be used with which minimum
conductor size?
A. 14 AWG
B. 12 AWG
C. 10 AWG
D. 8 AWG
Rationale: NEC Table 310.15 specifies that 12 AWG copper wire is
suitable for 20 amps.
6. The maximum number of 14 AWG conductors allowed in a 20-ampere
junction box is:
A. 2
B. 3
C. 4
D. 5
Rationale: NEC box fill calculations allow 5 current-carrying 14
AWG conductors in a standard single-gang box.
7. What type of conduit is non-metallic and often used in residential wet
locations?
A. EMT
B. RMC
C. PVC
D. IMC
Rationale: PVC conduit is non-metallic, corrosion-resistant, and
suitable for wet locations.
8. Which tool is used to measure insulation resistance?
A. Multimeter
B. Clamp meter
C. Megger
D. Voltmeter
Rationale: A megohmmeter (megger) is specifically designed to test
insulation resistance.
, 9. What is the NEC standard for arc-fault circuit interrupters in
bedrooms?
A. Optional
B. Required
C. Not allowed
D. Only in commercial buildings
Rationale: NEC 210.12 requires AFCIs in all bedroom circuits to
protect against arc faults.
10. The primary purpose of a bonding conductor is to:
A. Carry normal current
B. Ensure a low-resistance path to ground
C. Reduce voltage drop
D. Protect against overcurrent
Rationale: Bonding ensures all metal parts are at the same potential,
reducing shock risk.
11. Which type of grounding electrode is required for a residential
service?
A. Copper rod only
B. Concrete-encased electrode only
C. Any approved electrode like rod, pipe, or plate
D. None required
Rationale: NEC allows several types of approved grounding
electrodes for residential service.
12. Which device protects equipment from overcurrent but not from
ground faults?
A. Circuit breaker
B. GFCI
C. AFCI
D. Surge protector
Rationale: Circuit breakers protect conductors and equipment from
overcurrent but not ground faults.
13. In a 3-phase 4-wire system, the phase-to-phase voltage is 208V.
The phase-to-neutral voltage is:
A. 120V
B. 208V
C. 120V
D. 240V
