CO Journeyman Electrician Exam
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A| Instant Download Pdf
1. What is the primary purpose of a circuit breaker?
A. To increase voltage
B. To convert AC to DC
C. To protect a circuit from overcurrent
D. To step down voltage
Rationale: Circuit breakers are designed to interrupt excessive
current flow to prevent damage to wiring and equipment.
2. Which conductor color is typically used for grounding in the U.S.?
A. Red
B. Black
C. Green
D. White
Rationale: Green or bare copper is standard for grounding
conductors to ensure safety.
3. The NEC requires GFCI protection in which area?
A. Kitchens
B. Bathrooms
C. Both A and B
D. Bedrooms
Rationale: Ground Fault Circuit Interrupters (GFCIs) protect
against electric shock in wet locations like kitchens and bathrooms.
4. What is the unit of electrical resistance?
A. Volt
B. Ampere
C. Ohm
D. Watt
, Rationale: Resistance is measured in ohms, representing opposition
to current flow.
5. Which type of wiring is most commonly used in residential branch
circuits?
A. BX cable
B. NM cable (Romex)
C. MC cable
D. Conduit only
Rationale: Non-metallic sheathed cable (NM) is commonly used for
residential circuits due to ease of installation and cost-effectiveness.
6. What does the term “ampacity” refer to?
A. Voltage drop
B. Current-carrying capacity of a conductor
C. Resistance of a wire
D. Power consumption
Rationale: Ampacity is the maximum current a conductor can carry
safely without overheating.
7. Which device protects against short circuits and overloads?
A. Fuse
B. Circuit breaker
C. Transformer
D. Contactor
Rationale: Both fuses and circuit breakers interrupt excessive current
to protect equipment, but circuit breakers can be reset.
8. When connecting a 120V branch circuit, the hot wire is usually:
A. White
B. Green
C. Black or red
D. Bare copper
Rationale: Hot conductors in branch circuits are typically black or
red, carrying voltage from the source.
9. Which tool is used to measure electrical current?
A. Voltmeter
B. Ammeter
C. Ohmmeter
D. Wattmeter
Rationale: An ammeter is used to measure current in amperes.
, 10. What is the NEC minimum size copper grounding electrode
conductor for a typical residential service?
A. 6 AWG
B. 8 AWG
C. 4 AWG
D. 2 AWG
Rationale: According to NEC Table 250.66, a 4 AWG copper
conductor is required for grounding to a standard 100-200A service.
11. Which type of conduit is flexible and often used for machine
connections?
A. EMT
B. PVC
C. Flexible metal conduit (FMC)
D. RMC
Rationale: Flexible metal conduit is used where movement or
vibration occurs, allowing easy adjustments.
12. Which NEC article covers wiring methods?
A. 210
B. 300
C. 250
D. 110
Rationale: Article 300 of the NEC specifies general requirements for
wiring methods and materials.
13. What is the formula for calculating electrical power in a DC
circuit?
A. P = V / I
B. P = I^2 * R
C. P = V × I
D. P = R / I
Rationale: Electrical power in watts is the product of voltage and
current.
14. In a three-way switch configuration, how many travelers are
used?
A. 1
B. 2
C. 3
D. 4
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A| Instant Download Pdf
1. What is the primary purpose of a circuit breaker?
A. To increase voltage
B. To convert AC to DC
C. To protect a circuit from overcurrent
D. To step down voltage
Rationale: Circuit breakers are designed to interrupt excessive
current flow to prevent damage to wiring and equipment.
2. Which conductor color is typically used for grounding in the U.S.?
A. Red
B. Black
C. Green
D. White
Rationale: Green or bare copper is standard for grounding
conductors to ensure safety.
3. The NEC requires GFCI protection in which area?
A. Kitchens
B. Bathrooms
C. Both A and B
D. Bedrooms
Rationale: Ground Fault Circuit Interrupters (GFCIs) protect
against electric shock in wet locations like kitchens and bathrooms.
4. What is the unit of electrical resistance?
A. Volt
B. Ampere
C. Ohm
D. Watt
, Rationale: Resistance is measured in ohms, representing opposition
to current flow.
5. Which type of wiring is most commonly used in residential branch
circuits?
A. BX cable
B. NM cable (Romex)
C. MC cable
D. Conduit only
Rationale: Non-metallic sheathed cable (NM) is commonly used for
residential circuits due to ease of installation and cost-effectiveness.
6. What does the term “ampacity” refer to?
A. Voltage drop
B. Current-carrying capacity of a conductor
C. Resistance of a wire
D. Power consumption
Rationale: Ampacity is the maximum current a conductor can carry
safely without overheating.
7. Which device protects against short circuits and overloads?
A. Fuse
B. Circuit breaker
C. Transformer
D. Contactor
Rationale: Both fuses and circuit breakers interrupt excessive current
to protect equipment, but circuit breakers can be reset.
8. When connecting a 120V branch circuit, the hot wire is usually:
A. White
B. Green
C. Black or red
D. Bare copper
Rationale: Hot conductors in branch circuits are typically black or
red, carrying voltage from the source.
9. Which tool is used to measure electrical current?
A. Voltmeter
B. Ammeter
C. Ohmmeter
D. Wattmeter
Rationale: An ammeter is used to measure current in amperes.
, 10. What is the NEC minimum size copper grounding electrode
conductor for a typical residential service?
A. 6 AWG
B. 8 AWG
C. 4 AWG
D. 2 AWG
Rationale: According to NEC Table 250.66, a 4 AWG copper
conductor is required for grounding to a standard 100-200A service.
11. Which type of conduit is flexible and often used for machine
connections?
A. EMT
B. PVC
C. Flexible metal conduit (FMC)
D. RMC
Rationale: Flexible metal conduit is used where movement or
vibration occurs, allowing easy adjustments.
12. Which NEC article covers wiring methods?
A. 210
B. 300
C. 250
D. 110
Rationale: Article 300 of the NEC specifies general requirements for
wiring methods and materials.
13. What is the formula for calculating electrical power in a DC
circuit?
A. P = V / I
B. P = I^2 * R
C. P = V × I
D. P = R / I
Rationale: Electrical power in watts is the product of voltage and
current.
14. In a three-way switch configuration, how many travelers are
used?
A. 1
B. 2
C. 3
D. 4
