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ELECTRICAL WIRING RESIDENTIAL, 21ST EDITION EXAM 2026
QUESTIONS WITH VERIFIED QUESTIONS DETAILED RATIONALES
GRADED A+
ELECTRICAL WIRING RESIDENTIAL, 21ST EDITION: QUESTIONS WITH RATIONALES
SECTION 1: GENERAL INFORMATION & ELECTRICAL SAFETY
Questions 1–15
Question 1
What is the primary purpose of the National Electrical Code (NEC)?
A) To reduce construction costs
B) To establish minimum electrical safety standards
C) To increase electrical consumption
D) To regulate utility rates
Answer: B
Rationale: The NEC provides minimum requirements for safe electrical installations to protect
people and property from electrical hazards. Its primary goal is to safeguard persons and
property from electrical hazards, not to regulate costs, consumption, or utility rates.
Question 2
Which instrument is used to measure voltage?
A) Ammeter
B) Ohmmeter
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C) Voltmeter
D) Wattmeter
Answer: C
Rationale: A voltmeter measures electrical potential difference between two points in a circuit.
Question 3
According to Ohm's Law, voltage equals:
A) Current × Resistance
B) Current ÷ Resistance
C) Resistance ÷ Current
D) Power × Current
Answer: A
Rationale: Ohm's Law states V = I × R (Voltage = Current × Resistance).
Question 4
The unit of electrical resistance is:
A) Volt
B) Ampere
C) Watt
D) Ohm
Answer: D
Rationale: Resistance is measured in ohms (Ω). This is a fundamental electrical unit.
Question 5
A circuit breaker primarily protects against:
A) Low voltage
B) Overcurrent conditions
C) Moisture
D) Corrosion
Answer: B
Rationale: Circuit breakers open the circuit when current exceeds safe limits, protecting
conductors and equipment from overcurrent conditions.
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Question 6
The grounding conductor is primarily intended to:
A) Increase voltage
B) Carry normal load current
C) Provide a safe fault-current path
D) Reduce wire size
Answer: C
Rationale: Grounding helps clear faults quickly and reduces shock hazards by providing a low-
impedance path for fault current.
Question 7
A 15-amp branch circuit typically requires a minimum conductor size of:
A) 14 AWG copper
B) 12 AWG copper
C) 10 AWG copper
D) 8 AWG copper
Answer: A
Rationale: NEC commonly permits 14 AWG copper conductors on 15-amp circuits.
Question 8
What color insulation is commonly used for grounded (neutral) conductors?
A) Black
B) Red
C) White or gray
D) Green
Answer: C
Rationale: NEC identifies grounded conductors with white or gray insulation. This is a standard
identification requirement.
Question 9
Electrical power is measured in:
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A) Volts
B) Amperes
C) Watts
D) Ohms
Answer: C
Rationale: Power equals voltage multiplied by current (P = V × I), and the unit of power is the
watt.
Question 10
Lock Out Tag Out (LOTO) is a safety practice that requires:
A) Locking the panel door only
B) Tagging the panel directory
C) De-energizing equipment and applying locks and tags
D) Notifying the utility company
Answer: C
Rationale: LOTO is a safety practice that requires de-energizing equipment and applying locks
and tags to prevent accidental energization during work.
Question 11
Before beginning electrical work, the first safety step is to:
A) Turn on all lights
B) Test the circuit for voltage
C) De-energize the circuit and verify it is off
D) Notify the homeowner
Answer: C
Rationale: De-energizing the circuit and verifying it is off (testing for voltage) is the critical first
safety step before beginning any electrical work.
Question 12
What is the field term for a grounded conductor?
A) Hot
B) Neutral
ELECTRICAL WIRING RESIDENTIAL, 21ST EDITION EXAM 2026
QUESTIONS WITH VERIFIED QUESTIONS DETAILED RATIONALES
GRADED A+
ELECTRICAL WIRING RESIDENTIAL, 21ST EDITION: QUESTIONS WITH RATIONALES
SECTION 1: GENERAL INFORMATION & ELECTRICAL SAFETY
Questions 1–15
Question 1
What is the primary purpose of the National Electrical Code (NEC)?
A) To reduce construction costs
B) To establish minimum electrical safety standards
C) To increase electrical consumption
D) To regulate utility rates
Answer: B
Rationale: The NEC provides minimum requirements for safe electrical installations to protect
people and property from electrical hazards. Its primary goal is to safeguard persons and
property from electrical hazards, not to regulate costs, consumption, or utility rates.
Question 2
Which instrument is used to measure voltage?
A) Ammeter
B) Ohmmeter
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C) Voltmeter
D) Wattmeter
Answer: C
Rationale: A voltmeter measures electrical potential difference between two points in a circuit.
Question 3
According to Ohm's Law, voltage equals:
A) Current × Resistance
B) Current ÷ Resistance
C) Resistance ÷ Current
D) Power × Current
Answer: A
Rationale: Ohm's Law states V = I × R (Voltage = Current × Resistance).
Question 4
The unit of electrical resistance is:
A) Volt
B) Ampere
C) Watt
D) Ohm
Answer: D
Rationale: Resistance is measured in ohms (Ω). This is a fundamental electrical unit.
Question 5
A circuit breaker primarily protects against:
A) Low voltage
B) Overcurrent conditions
C) Moisture
D) Corrosion
Answer: B
Rationale: Circuit breakers open the circuit when current exceeds safe limits, protecting
conductors and equipment from overcurrent conditions.
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Question 6
The grounding conductor is primarily intended to:
A) Increase voltage
B) Carry normal load current
C) Provide a safe fault-current path
D) Reduce wire size
Answer: C
Rationale: Grounding helps clear faults quickly and reduces shock hazards by providing a low-
impedance path for fault current.
Question 7
A 15-amp branch circuit typically requires a minimum conductor size of:
A) 14 AWG copper
B) 12 AWG copper
C) 10 AWG copper
D) 8 AWG copper
Answer: A
Rationale: NEC commonly permits 14 AWG copper conductors on 15-amp circuits.
Question 8
What color insulation is commonly used for grounded (neutral) conductors?
A) Black
B) Red
C) White or gray
D) Green
Answer: C
Rationale: NEC identifies grounded conductors with white or gray insulation. This is a standard
identification requirement.
Question 9
Electrical power is measured in:
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A) Volts
B) Amperes
C) Watts
D) Ohms
Answer: C
Rationale: Power equals voltage multiplied by current (P = V × I), and the unit of power is the
watt.
Question 10
Lock Out Tag Out (LOTO) is a safety practice that requires:
A) Locking the panel door only
B) Tagging the panel directory
C) De-energizing equipment and applying locks and tags
D) Notifying the utility company
Answer: C
Rationale: LOTO is a safety practice that requires de-energizing equipment and applying locks
and tags to prevent accidental energization during work.
Question 11
Before beginning electrical work, the first safety step is to:
A) Turn on all lights
B) Test the circuit for voltage
C) De-energize the circuit and verify it is off
D) Notify the homeowner
Answer: C
Rationale: De-energizing the circuit and verifying it is off (testing for voltage) is the critical first
safety step before beginning any electrical work.
Question 12
What is the field term for a grounded conductor?
A) Hot
B) Neutral
