CO Residential Wireman Exam
Questions and Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf
1. What is the primary purpose of the National Electrical Code
(NEC)?
A. To establish electrical utility rates
B. To regulate electrical contractor licensing fees
C. To provide practical safeguards for persons and property from
electrical hazards
D. To specify the design of electrical appliances
Rationale: The NEC establishes minimum requirements intended to
safeguard people and property from hazards arising from the use of
electricity. It is primarily a safety standard rather than a design manual
or utility-rate document.
, 2. Which voltage is commonly supplied to a standard single-phase
residential dwelling in the United States?
A. 120/208 volts
B. 120/240 volts
C. 120/240 volts, single phase, three wire
D. 240/480 volts
Rationale: Typical North American residences receive a 120/240-volt
single-phase service. The system has two ungrounded conductors and a
grounded conductor, providing 120 volts from either ungrounded
conductor to the neutral and 240 volts between the two ungrounded
conductors.
3. What is the minimum number of 20-ampere small-appliance
branch circuits generally required for a dwelling kitchen?
A. One
B. Two
C. Three
D. Four
Rationale: The NEC requires at least two 20-ampere small-appliance
branch circuits for receptacle outlets in dwelling-unit kitchens, dining
areas, pantries, breakfast rooms, and similar areas. These circuits help
prevent overloading from portable kitchen appliances.
, 4. Which conductor is normally identified by white or gray
insulation?
A. Equipment grounding conductor
B. Ungrounded conductor
C. Grounded conductor
D. Bonding jumper
Rationale: The grounded conductor, commonly called the neutral
conductor, is generally identified by a continuous white or gray finish or
permitted identification methods. Green is reserved for equipment
grounding conductors.
5. What is the primary function of an equipment grounding
conductor?
A. Carry normal circuit current
B. Increase circuit voltage
C. Reduce conductor resistance
D. Provide a low-impedance path for fault current
Rationale: An equipment grounding conductor provides a conductive
path for fault current back to the source. This path allows overcurrent
protective devices to operate promptly when a fault energizes exposed
metal parts.
, 6. A 20-ampere branch circuit is being installed using copper
conductors. Which conductor size is generally appropriate for the
circuit?
A. 18 AWG
B. 16 AWG
C. 12 AWG
D. 10 AWG
Rationale: Copper 12 AWG conductors are commonly used for 20-
ampere branch circuits under the NEC ampacity rules. The actual
conductor selection must also consider conditions of use, terminal
ratings, adjustment, and other applicable requirements.
7. What device is designed to interrupt a circuit when it detects a
dangerous imbalance between current leaving and returning on
the circuit conductors?
A. AFCI
B. Circuit breaker
C. GFCI
D. Surge protector
Rationale: A ground-fault circuit interrupter monitors the current
balance between the circuit conductors. When the difference reaches its
Questions and Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf
1. What is the primary purpose of the National Electrical Code
(NEC)?
A. To establish electrical utility rates
B. To regulate electrical contractor licensing fees
C. To provide practical safeguards for persons and property from
electrical hazards
D. To specify the design of electrical appliances
Rationale: The NEC establishes minimum requirements intended to
safeguard people and property from hazards arising from the use of
electricity. It is primarily a safety standard rather than a design manual
or utility-rate document.
, 2. Which voltage is commonly supplied to a standard single-phase
residential dwelling in the United States?
A. 120/208 volts
B. 120/240 volts
C. 120/240 volts, single phase, three wire
D. 240/480 volts
Rationale: Typical North American residences receive a 120/240-volt
single-phase service. The system has two ungrounded conductors and a
grounded conductor, providing 120 volts from either ungrounded
conductor to the neutral and 240 volts between the two ungrounded
conductors.
3. What is the minimum number of 20-ampere small-appliance
branch circuits generally required for a dwelling kitchen?
A. One
B. Two
C. Three
D. Four
Rationale: The NEC requires at least two 20-ampere small-appliance
branch circuits for receptacle outlets in dwelling-unit kitchens, dining
areas, pantries, breakfast rooms, and similar areas. These circuits help
prevent overloading from portable kitchen appliances.
, 4. Which conductor is normally identified by white or gray
insulation?
A. Equipment grounding conductor
B. Ungrounded conductor
C. Grounded conductor
D. Bonding jumper
Rationale: The grounded conductor, commonly called the neutral
conductor, is generally identified by a continuous white or gray finish or
permitted identification methods. Green is reserved for equipment
grounding conductors.
5. What is the primary function of an equipment grounding
conductor?
A. Carry normal circuit current
B. Increase circuit voltage
C. Reduce conductor resistance
D. Provide a low-impedance path for fault current
Rationale: An equipment grounding conductor provides a conductive
path for fault current back to the source. This path allows overcurrent
protective devices to operate promptly when a fault energizes exposed
metal parts.
, 6. A 20-ampere branch circuit is being installed using copper
conductors. Which conductor size is generally appropriate for the
circuit?
A. 18 AWG
B. 16 AWG
C. 12 AWG
D. 10 AWG
Rationale: Copper 12 AWG conductors are commonly used for 20-
ampere branch circuits under the NEC ampacity rules. The actual
conductor selection must also consider conditions of use, terminal
ratings, adjustment, and other applicable requirements.
7. What device is designed to interrupt a circuit when it detects a
dangerous imbalance between current leaving and returning on
the circuit conductors?
A. AFCI
B. Circuit breaker
C. GFCI
D. Surge protector
Rationale: A ground-fault circuit interrupter monitors the current
balance between the circuit conductors. When the difference reaches its
