CALIFORNIA CONTRACTORS STATE LICENSE BOARD
(CSLB) C-10 ELECTRICAL CONTRACTOR EXAM,
QUESTIONS AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A |
INSTANT DOWNLOAD PDF.
1–50 C-10 Electrical Contractor Practice Questions
1. Which of the following is the minimum clearance required for
working space in front of an electrical panel?
A. 24 inches
B. 30 inches
C. 36 inches
D. 48 inches
Answer: C
Rationale: NEC 110.26 requires a minimum of 36 inches of working
space in front of electrical panels for safe operation.
2. What is the maximum number of conductors allowed in a standard
4-inch square junction box?
A. 4
B. 6
C. 8
D. 10
Answer: C
Rationale: NEC Table 314.16(B) allows up to 8 conductors for a standard
4-inch square box, based on box fill calculations.
,3. What is the standard voltage for most residential lighting circuits in
California?
A. 120 V
B. 208 V
C. 240 V
D. 277 V
Answer: A
Rationale: Standard residential circuits in California are 120 volts for
general lighting and receptacles.
4. What type of conductor is typically required for outdoor wiring
exposed to sunlight?
A. THHN
B. UF
C. NM-B
D. SER
Answer: B
Rationale: UF cable is rated for direct burial and outdoor exposure,
while NM-B is only for dry indoor locations.
5. Which device is used to protect people from electrical shock?
A. Circuit breaker
B. Fuse
C. GFCI
D. Contactor
Answer: C
,Rationale: Ground Fault Circuit Interrupters (GFCIs) detect small current
leaks and shut off power to prevent shock.
6. The maximum allowable voltage drop for branch circuits in a
dwelling is:
A. 2%
B. 3%
C. 5%
D. 10%
Answer: B
Rationale: NEC recommends a maximum voltage drop of 3% for branch
circuits to maintain efficiency and performance.
7. In a three-phase system, the phase-to-phase voltage is 208 V. What
is the phase-to-neutral voltage?
A. 120 V
B. 208 V
C. 240 V
D. 277 V
Answer: A
Rationale: For a 208/120 V three-phase system, phase-to-neutral
voltage = 208 ÷ √3 ≈ 120 V.
8. What is the minimum burial depth for a 120 V, 20 A UF cable in a
residential driveway?
A. 6 inches
B. 12 inches
C. 18 inches
, D. 24 inches
Answer: B
Rationale: NEC Table 300.5 specifies 12 inches minimum for UF cable
under residential driveways.
9. Which of the following is considered a load that requires a
dedicated circuit in a kitchen?
A. Refrigerator
B. Dishwasher
C. Microwave
D. All of the above
Answer: D
Rationale: NEC requires major kitchen appliances to have dedicated
circuits to prevent overloads.
10. Which conductor color is typically used for a grounding conductor?
A. Black
B. Red
C. Green
D. White
Answer: C
Rationale: Green or bare copper conductors are standard for grounding.
11. The NEC requires AFCI protection in which areas of a dwelling?
A. Kitchens
B. Bathrooms
C. Bedrooms
D. Garages
(CSLB) C-10 ELECTRICAL CONTRACTOR EXAM,
QUESTIONS AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A |
INSTANT DOWNLOAD PDF.
1–50 C-10 Electrical Contractor Practice Questions
1. Which of the following is the minimum clearance required for
working space in front of an electrical panel?
A. 24 inches
B. 30 inches
C. 36 inches
D. 48 inches
Answer: C
Rationale: NEC 110.26 requires a minimum of 36 inches of working
space in front of electrical panels for safe operation.
2. What is the maximum number of conductors allowed in a standard
4-inch square junction box?
A. 4
B. 6
C. 8
D. 10
Answer: C
Rationale: NEC Table 314.16(B) allows up to 8 conductors for a standard
4-inch square box, based on box fill calculations.
,3. What is the standard voltage for most residential lighting circuits in
California?
A. 120 V
B. 208 V
C. 240 V
D. 277 V
Answer: A
Rationale: Standard residential circuits in California are 120 volts for
general lighting and receptacles.
4. What type of conductor is typically required for outdoor wiring
exposed to sunlight?
A. THHN
B. UF
C. NM-B
D. SER
Answer: B
Rationale: UF cable is rated for direct burial and outdoor exposure,
while NM-B is only for dry indoor locations.
5. Which device is used to protect people from electrical shock?
A. Circuit breaker
B. Fuse
C. GFCI
D. Contactor
Answer: C
,Rationale: Ground Fault Circuit Interrupters (GFCIs) detect small current
leaks and shut off power to prevent shock.
6. The maximum allowable voltage drop for branch circuits in a
dwelling is:
A. 2%
B. 3%
C. 5%
D. 10%
Answer: B
Rationale: NEC recommends a maximum voltage drop of 3% for branch
circuits to maintain efficiency and performance.
7. In a three-phase system, the phase-to-phase voltage is 208 V. What
is the phase-to-neutral voltage?
A. 120 V
B. 208 V
C. 240 V
D. 277 V
Answer: A
Rationale: For a 208/120 V three-phase system, phase-to-neutral
voltage = 208 ÷ √3 ≈ 120 V.
8. What is the minimum burial depth for a 120 V, 20 A UF cable in a
residential driveway?
A. 6 inches
B. 12 inches
C. 18 inches
, D. 24 inches
Answer: B
Rationale: NEC Table 300.5 specifies 12 inches minimum for UF cable
under residential driveways.
9. Which of the following is considered a load that requires a
dedicated circuit in a kitchen?
A. Refrigerator
B. Dishwasher
C. Microwave
D. All of the above
Answer: D
Rationale: NEC requires major kitchen appliances to have dedicated
circuits to prevent overloads.
10. Which conductor color is typically used for a grounding conductor?
A. Black
B. Red
C. Green
D. White
Answer: C
Rationale: Green or bare copper conductors are standard for grounding.
11. The NEC requires AFCI protection in which areas of a dwelling?
A. Kitchens
B. Bathrooms
C. Bedrooms
D. Garages
