AZ L-31 Electrical Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. Which of the following is the standard voltage for residential electrical
service in the United States?
A) 120/240V
B) 208/240V
C) 110/220V
D) 100/200V
A) 120/240V
Rationale: Standard residential service in the U.S. provides 120 volts
for most appliances and 240 volts for high-power appliances.
2. What is the main purpose of a circuit breaker?
A) To store electrical energy
B) To provide a backup power supply
C) To interrupt current flow in case of overload or short circuit
D) To convert AC to DC
C) To interrupt current flow in case of overload or short circuit
Rationale: Circuit breakers protect wiring and equipment by
disconnecting power when excessive current is detected.
3. Which type of conductor is most commonly used in residential wiring?
A) Aluminum
B) Copper
C) Steel
D) Silver
B) Copper
Rationale: Copper is preferred for residential wiring because of its
excellent conductivity and durability.
,4. What is the NEC requirement for grounding a residential electrical
system?
A) It must be grounded to a water pipe or grounding rod
B) Grounding is optional in residences
C) Only the main panel must be grounded
D) Each outlet must have a separate ground rod
A) It must be grounded to a water pipe or grounding rod
Rationale: The NEC requires residential systems to be grounded to
prevent electric shock and ensure safe operation.
5. In a 3-phase system, what is the voltage between two phases in a 208V
wye system?
A) 120V
B) 208V
C) 240V
D) 480V
B) 208V
Rationale: In a 208V wye system, the line-to-line voltage is 208 volts.
6. What is the purpose of a GFCI (Ground Fault Circuit Interrupter)?
A) To prevent overloading circuits
B) To protect against electrocution from ground faults
C) To stabilize voltage fluctuations
D) To provide surge protection
B) To protect against electrocution from ground faults
Rationale: GFCIs monitor current imbalance between hot and
neutral wires and trip if leakage occurs.
7. Which of the following color codes is commonly used for grounding
conductors in the U.S.?
A) Black
B) Red
C) Green or bare
D) White
C) Green or bare
Rationale: NEC specifies green or bare copper for grounding to
identify it clearly and prevent misuse.
8. When installing conduit in a residential building, which type is often
used outdoors?
A) EMT (Electrical Metallic Tubing)
, B) PVC
C) NM-B cable
D) MC cable
B) PVC
Rationale: PVC conduit is non-metallic, corrosion-resistant, and
suitable for outdoor use.
9. What is the maximum load allowed on a 15A residential circuit
according to the NEC?
A) 1200W
B) 1500W
C) 1800W
D) 2000W
C) 1800W
Rationale: Maximum continuous load is 80% of rated capacity: 15A
× 120V × 0.8 = 1440W (rounded to 1800W for calculation purposes).
10. Which type of wiring is typically used in new residential
construction?
A) BX cable
B) NM-B cable
C) UF cable
D) SE cable
B) NM-B cable
Rationale: NM-B (Non-Metallic Sheathed) cable is commonly used
for indoor wiring in residential construction.
11. What is the primary function of a transformer?
A) To convert AC to DC
B) To step up or step down voltage levels
C) To store electrical energy
D) To protect circuits from overload
B) To step up or step down voltage levels
Rationale: Transformers change voltage levels while maintaining the
same frequency.
12. Which device is used to measure current in a circuit?
A) Voltmeter
B) Ammeter
C) Ohmmeter
D) Wattmeter
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. Which of the following is the standard voltage for residential electrical
service in the United States?
A) 120/240V
B) 208/240V
C) 110/220V
D) 100/200V
A) 120/240V
Rationale: Standard residential service in the U.S. provides 120 volts
for most appliances and 240 volts for high-power appliances.
2. What is the main purpose of a circuit breaker?
A) To store electrical energy
B) To provide a backup power supply
C) To interrupt current flow in case of overload or short circuit
D) To convert AC to DC
C) To interrupt current flow in case of overload or short circuit
Rationale: Circuit breakers protect wiring and equipment by
disconnecting power when excessive current is detected.
3. Which type of conductor is most commonly used in residential wiring?
A) Aluminum
B) Copper
C) Steel
D) Silver
B) Copper
Rationale: Copper is preferred for residential wiring because of its
excellent conductivity and durability.
,4. What is the NEC requirement for grounding a residential electrical
system?
A) It must be grounded to a water pipe or grounding rod
B) Grounding is optional in residences
C) Only the main panel must be grounded
D) Each outlet must have a separate ground rod
A) It must be grounded to a water pipe or grounding rod
Rationale: The NEC requires residential systems to be grounded to
prevent electric shock and ensure safe operation.
5. In a 3-phase system, what is the voltage between two phases in a 208V
wye system?
A) 120V
B) 208V
C) 240V
D) 480V
B) 208V
Rationale: In a 208V wye system, the line-to-line voltage is 208 volts.
6. What is the purpose of a GFCI (Ground Fault Circuit Interrupter)?
A) To prevent overloading circuits
B) To protect against electrocution from ground faults
C) To stabilize voltage fluctuations
D) To provide surge protection
B) To protect against electrocution from ground faults
Rationale: GFCIs monitor current imbalance between hot and
neutral wires and trip if leakage occurs.
7. Which of the following color codes is commonly used for grounding
conductors in the U.S.?
A) Black
B) Red
C) Green or bare
D) White
C) Green or bare
Rationale: NEC specifies green or bare copper for grounding to
identify it clearly and prevent misuse.
8. When installing conduit in a residential building, which type is often
used outdoors?
A) EMT (Electrical Metallic Tubing)
, B) PVC
C) NM-B cable
D) MC cable
B) PVC
Rationale: PVC conduit is non-metallic, corrosion-resistant, and
suitable for outdoor use.
9. What is the maximum load allowed on a 15A residential circuit
according to the NEC?
A) 1200W
B) 1500W
C) 1800W
D) 2000W
C) 1800W
Rationale: Maximum continuous load is 80% of rated capacity: 15A
× 120V × 0.8 = 1440W (rounded to 1800W for calculation purposes).
10. Which type of wiring is typically used in new residential
construction?
A) BX cable
B) NM-B cable
C) UF cable
D) SE cable
B) NM-B cable
Rationale: NM-B (Non-Metallic Sheathed) cable is commonly used
for indoor wiring in residential construction.
11. What is the primary function of a transformer?
A) To convert AC to DC
B) To step up or step down voltage levels
C) To store electrical energy
D) To protect circuits from overload
B) To step up or step down voltage levels
Rationale: Transformers change voltage levels while maintaining the
same frequency.
12. Which device is used to measure current in a circuit?
A) Voltmeter
B) Ammeter
C) Ohmmeter
D) Wattmeter
