AL EL Electrical Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the standard voltage for residential electrical outlets in the
United States?
A. 1200V
B. 240V
C. 120V
D. 208V
Rationale: Residential outlets in the U.S. are typically 120 volts.
2. Which type of wire is most commonly used for residential branch
circuits?
A. THHN
B. NM (Non-Metallic) Sheathed Cable
C. UF-B
D. MC Cable
Rationale: NM cable, also known as Romex, is standard for indoor
residential wiring.
3. In a three-phase system, what is the phase-to-phase voltage if the
phase-to-neutral voltage is 120V?
A. 120V
B. 208V
C. 208V
D. 240V
Rationale: In a three-phase 120V system, phase-to-phase voltage is
120V × √3 ≈ 208V.
,4. The NEC requires that grounded conductors be what color?
A. Black
B. Red
C. White or gray
D. Green
Rationale: White or gray is designated for grounded (neutral)
conductors.
5. Which device protects a circuit from overcurrent?
A. GFCI
B. AFCI
C. Circuit Breaker
D. Switch
Rationale: Circuit breakers or fuses interrupt current flow in case of
overload or short circuit.
6. A GFCI outlet is designed to trip at what leakage current?
A. 10 mA
B. 15 mA
C. 5 mA
D. 20 mA
Rationale: GFCIs trip when they detect a ground fault of about 5
milliamps.
7. What is the purpose of an AFCI?
A. Protect against overvoltage
B. Protect against arc faults
C. Prevent ground faults
D. Measure voltage
Rationale: AFCIs detect arcing conditions that could cause fires in
wiring.
8. The main advantage of aluminum wiring over copper is:
A. Lower cost
B. Higher conductivity
C. Corrosion resistance
D. Smaller size
Rationale: Aluminum wiring is cheaper but has higher resistance
than copper.
9. What is the minimum wire size for a 20-amp residential branch circuit?
A. 12 AWG
, B. 12 AWG
C. 10 AWG
D. 14 AWG
Rationale: NEC specifies 12 AWG copper for 20A circuits.
10. What is the primary function of a transformer?
A. Convert AC to DC
B. Step current up
C. Step voltage up or down
D. Step voltage up or down
Rationale: Transformers change voltage levels while keeping power
nearly constant.
11. Which conductor is considered “hot” in a typical residential
single-phase circuit?
A. Green
B. White
C. Black or red
D. Bare
Rationale: Black or red wires carry the live current in residential
circuits.
12. Which of the following is a common residential lighting control
method?
A. Step-up transformer
B. Breaker panel
C. Dimmer switch
D. AFCI
Rationale: Dimmer switches control the brightness by adjusting
current to the fixture.
13. NEC Article 250 deals with:
A. Overcurrent protection
B. Grounding and bonding
C. Wiring methods
D. Voltage ratings
Rationale: Article 250 covers grounding and bonding requirements to
ensure electrical safety.
14. The minimum height for a service disconnect in a residential
building is:
A. 4 feet
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the standard voltage for residential electrical outlets in the
United States?
A. 1200V
B. 240V
C. 120V
D. 208V
Rationale: Residential outlets in the U.S. are typically 120 volts.
2. Which type of wire is most commonly used for residential branch
circuits?
A. THHN
B. NM (Non-Metallic) Sheathed Cable
C. UF-B
D. MC Cable
Rationale: NM cable, also known as Romex, is standard for indoor
residential wiring.
3. In a three-phase system, what is the phase-to-phase voltage if the
phase-to-neutral voltage is 120V?
A. 120V
B. 208V
C. 208V
D. 240V
Rationale: In a three-phase 120V system, phase-to-phase voltage is
120V × √3 ≈ 208V.
,4. The NEC requires that grounded conductors be what color?
A. Black
B. Red
C. White or gray
D. Green
Rationale: White or gray is designated for grounded (neutral)
conductors.
5. Which device protects a circuit from overcurrent?
A. GFCI
B. AFCI
C. Circuit Breaker
D. Switch
Rationale: Circuit breakers or fuses interrupt current flow in case of
overload or short circuit.
6. A GFCI outlet is designed to trip at what leakage current?
A. 10 mA
B. 15 mA
C. 5 mA
D. 20 mA
Rationale: GFCIs trip when they detect a ground fault of about 5
milliamps.
7. What is the purpose of an AFCI?
A. Protect against overvoltage
B. Protect against arc faults
C. Prevent ground faults
D. Measure voltage
Rationale: AFCIs detect arcing conditions that could cause fires in
wiring.
8. The main advantage of aluminum wiring over copper is:
A. Lower cost
B. Higher conductivity
C. Corrosion resistance
D. Smaller size
Rationale: Aluminum wiring is cheaper but has higher resistance
than copper.
9. What is the minimum wire size for a 20-amp residential branch circuit?
A. 12 AWG
, B. 12 AWG
C. 10 AWG
D. 14 AWG
Rationale: NEC specifies 12 AWG copper for 20A circuits.
10. What is the primary function of a transformer?
A. Convert AC to DC
B. Step current up
C. Step voltage up or down
D. Step voltage up or down
Rationale: Transformers change voltage levels while keeping power
nearly constant.
11. Which conductor is considered “hot” in a typical residential
single-phase circuit?
A. Green
B. White
C. Black or red
D. Bare
Rationale: Black or red wires carry the live current in residential
circuits.
12. Which of the following is a common residential lighting control
method?
A. Step-up transformer
B. Breaker panel
C. Dimmer switch
D. AFCI
Rationale: Dimmer switches control the brightness by adjusting
current to the fixture.
13. NEC Article 250 deals with:
A. Overcurrent protection
B. Grounding and bonding
C. Wiring methods
D. Voltage ratings
Rationale: Article 250 covers grounding and bonding requirements to
ensure electrical safety.
14. The minimum height for a service disconnect in a residential
building is:
A. 4 feet
