Colorado Residential Wireman License
Examination Practice Exam 2026 | 100
Questions & Answers with Detailed
Rationales | Complete Colorado
Residential Wireman Exam Prep &
Study Guide
1. What is the primary purpose of the National Electrical Code (NEC)?
A. To establish electrical utility rates
B. To provide practical safeguards for persons and property from electrical
hazards
C. To regulate electrical equipment manufacturers
D. To determine electrician wages
Answer: To provide practical safeguards for persons and property from electrical
hazards
Rationale: The NEC establishes minimum requirements intended to protect
people and property from hazards arising from the use of electricity.
2. Which NEC article primarily covers branch circuits?
A. Article 110
B. Article 210
,C. Article 250
D. Article 300
Answer: Article 210
Rationale: NEC Article 210 contains requirements for branch circuits, including
their ratings, required outlets, conductors, and overcurrent protection.
3. What is the standard nominal voltage commonly supplied to a single-family
residence?
A. 120/240 volts
B. 208/480 volts
C. 277/480 volts
D. 120/208 volts only
Answer: 120/240 volts
Rationale: Typical dwelling services use a 120/240-volt single-phase system,
providing approximately 120 volts from either ungrounded conductor to neutral
and 240 volts between the ungrounded conductors.
4. What is the primary purpose of an overcurrent protective device?
A. To increase circuit voltage
B. To limit conductor temperature by interrupting excessive current
C. To improve power factor
D. To increase conductor resistance
Answer: To limit conductor temperature by interrupting excessive current
Rationale: Fuses and circuit breakers protect conductors and equipment by
opening the circuit when current exceeds allowable levels.
5. Which conductor normally carries current back to the source in a 120-volt
circuit?
,A. Equipment grounding conductor
B. Grounding electrode conductor
C. Neutral conductor
D. Bonding jumper
Answer: Neutral conductor
Rationale: In a typical 120-volt circuit, the grounded conductor, commonly called
the neutral, provides the return path for load current.
6. What color is normally used to identify an equipment grounding
conductor?
A. White
B. Gray
C. Green or bare
D. Orange
Answer: Green or bare
Rationale: Equipment grounding conductors are generally identified by green
insulation, green with a yellow stripe, or by being bare.
7. What is the standard rating of a 15-ampere branch circuit?
A. 10 amperes
B. 15 amperes
C. 20 amperes
D. 30 amperes
Answer: 15 amperes
Rationale: A 15-ampere branch circuit is generally protected by a 15-ampere
overcurrent device, subject to applicable NEC requirements.
8. Which conductor size is commonly used for a 20-ampere branch circuit?
, A. 12 AWG copper
B. 14 AWG copper
C. 10 AWG copper
D. 8 AWG copper
Answer: 12 AWG copper
Rationale: 12 AWG copper is commonly used for 20-ampere branch circuits
under applicable ampacity rules.
9. What is the primary function of a circuit breaker?
A. Store electrical energy
B. Interrupt current when an overcurrent condition occurs
C. Reduce conductor size
D. Increase circuit voltage
Answer: Interrupt current when an overcurrent condition occurs
Rationale: A circuit breaker automatically opens a circuit when its trip
mechanism detects an overcurrent condition.
10.What does GFCI stand for?
A. Ground-Fault Circuit Interrupter
B. Grounded-Frequency Circuit Indicator
C. General Fault Current Isolator
D. Grounded Feeder Circuit Interlock
Answer: Ground-Fault Circuit Interrupter
Rationale: A GFCI monitors current and disconnects the circuit when it detects
an imbalance associated with current leakage to ground.
11.What is the primary purpose of GFCI protection?
A. Protect against excessive voltage
B. Protect people from electric shock caused by ground-fault current
Examination Practice Exam 2026 | 100
Questions & Answers with Detailed
Rationales | Complete Colorado
Residential Wireman Exam Prep &
Study Guide
1. What is the primary purpose of the National Electrical Code (NEC)?
A. To establish electrical utility rates
B. To provide practical safeguards for persons and property from electrical
hazards
C. To regulate electrical equipment manufacturers
D. To determine electrician wages
Answer: To provide practical safeguards for persons and property from electrical
hazards
Rationale: The NEC establishes minimum requirements intended to protect
people and property from hazards arising from the use of electricity.
2. Which NEC article primarily covers branch circuits?
A. Article 110
B. Article 210
,C. Article 250
D. Article 300
Answer: Article 210
Rationale: NEC Article 210 contains requirements for branch circuits, including
their ratings, required outlets, conductors, and overcurrent protection.
3. What is the standard nominal voltage commonly supplied to a single-family
residence?
A. 120/240 volts
B. 208/480 volts
C. 277/480 volts
D. 120/208 volts only
Answer: 120/240 volts
Rationale: Typical dwelling services use a 120/240-volt single-phase system,
providing approximately 120 volts from either ungrounded conductor to neutral
and 240 volts between the ungrounded conductors.
4. What is the primary purpose of an overcurrent protective device?
A. To increase circuit voltage
B. To limit conductor temperature by interrupting excessive current
C. To improve power factor
D. To increase conductor resistance
Answer: To limit conductor temperature by interrupting excessive current
Rationale: Fuses and circuit breakers protect conductors and equipment by
opening the circuit when current exceeds allowable levels.
5. Which conductor normally carries current back to the source in a 120-volt
circuit?
,A. Equipment grounding conductor
B. Grounding electrode conductor
C. Neutral conductor
D. Bonding jumper
Answer: Neutral conductor
Rationale: In a typical 120-volt circuit, the grounded conductor, commonly called
the neutral, provides the return path for load current.
6. What color is normally used to identify an equipment grounding
conductor?
A. White
B. Gray
C. Green or bare
D. Orange
Answer: Green or bare
Rationale: Equipment grounding conductors are generally identified by green
insulation, green with a yellow stripe, or by being bare.
7. What is the standard rating of a 15-ampere branch circuit?
A. 10 amperes
B. 15 amperes
C. 20 amperes
D. 30 amperes
Answer: 15 amperes
Rationale: A 15-ampere branch circuit is generally protected by a 15-ampere
overcurrent device, subject to applicable NEC requirements.
8. Which conductor size is commonly used for a 20-ampere branch circuit?
, A. 12 AWG copper
B. 14 AWG copper
C. 10 AWG copper
D. 8 AWG copper
Answer: 12 AWG copper
Rationale: 12 AWG copper is commonly used for 20-ampere branch circuits
under applicable ampacity rules.
9. What is the primary function of a circuit breaker?
A. Store electrical energy
B. Interrupt current when an overcurrent condition occurs
C. Reduce conductor size
D. Increase circuit voltage
Answer: Interrupt current when an overcurrent condition occurs
Rationale: A circuit breaker automatically opens a circuit when its trip
mechanism detects an overcurrent condition.
10.What does GFCI stand for?
A. Ground-Fault Circuit Interrupter
B. Grounded-Frequency Circuit Indicator
C. General Fault Current Isolator
D. Grounded Feeder Circuit Interlock
Answer: Ground-Fault Circuit Interrupter
Rationale: A GFCI monitors current and disconnects the circuit when it detects
an imbalance associated with current leakage to ground.
11.What is the primary purpose of GFCI protection?
A. Protect against excessive voltage
B. Protect people from electric shock caused by ground-fault current
