CSLB C10 Electrical Exam Test 1 (2025):
100 Questions with 100% Verified Correct
Answers & Detailed Rationales
Prepared for Electrical Contractor License Preparation
July 28, 2025
,Contents
1 Exam Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
1
, CSLB C10 Electrical Exam Test 1 (2025) 2 of 27
1 Exam Questions and Answers
Question 1: What is the minimum size copper conductor required for a 20-ampere branch
circuit operating at 120 volts?
a) 14 AWG
b) 12 AWG
c) 10 AWG
d) 8 AWG
Correct Answer: b) 12 AWG
Rationale: The National Electrical Code (NEC) Table 310.15(B)(16) spec-
ifies that for a 20-ampere branch circuit using copper conductors at 60°C,
the minimum conductor size is 12 AWG, rated for 20 amperes. This ensures
the conductor can safely carry the current without overheating, considering
typical insulation ratings for branch circuits.
Question 2: How many 12 AWG conductors can be installed in a 4-inch square box with
a depth of 1.5 inches?
a) 6
b) 9
c) 12
d) 15
Correct Answer: b) 9
Rationale: NEC Table 314.16(A) indicates that a 4-inch square box with a
1.5-inch depth has a volume of 21 cubic inches. Each 12 AWG conductor
requires 2.25 cubic inches, so the maximum number of conductors is 21 ÷
2.25 = 9.33, rounded down to 9 to comply with box fill requirements.
Question 3: Which conduit type is required for an underground installation subject to
severe physical damage?
a) EMT
b) PVC
c) RMC
d) FMC
Correct Answer: c) RMC
Rationale: Rigid Metal Conduit (RMC) is mandated by NEC Article 344 for
underground installations exposed to severe physical damage due to its high
strength and durability. RMC protects conductors in harsh environments
better than EMT, PVC, or FMC.
Question 4: What is the minimum working clearance required in front of a 480-volt elec-
trical panel?
100 Questions with 100% Verified Correct
Answers & Detailed Rationales
Prepared for Electrical Contractor License Preparation
July 28, 2025
,Contents
1 Exam Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
1
, CSLB C10 Electrical Exam Test 1 (2025) 2 of 27
1 Exam Questions and Answers
Question 1: What is the minimum size copper conductor required for a 20-ampere branch
circuit operating at 120 volts?
a) 14 AWG
b) 12 AWG
c) 10 AWG
d) 8 AWG
Correct Answer: b) 12 AWG
Rationale: The National Electrical Code (NEC) Table 310.15(B)(16) spec-
ifies that for a 20-ampere branch circuit using copper conductors at 60°C,
the minimum conductor size is 12 AWG, rated for 20 amperes. This ensures
the conductor can safely carry the current without overheating, considering
typical insulation ratings for branch circuits.
Question 2: How many 12 AWG conductors can be installed in a 4-inch square box with
a depth of 1.5 inches?
a) 6
b) 9
c) 12
d) 15
Correct Answer: b) 9
Rationale: NEC Table 314.16(A) indicates that a 4-inch square box with a
1.5-inch depth has a volume of 21 cubic inches. Each 12 AWG conductor
requires 2.25 cubic inches, so the maximum number of conductors is 21 ÷
2.25 = 9.33, rounded down to 9 to comply with box fill requirements.
Question 3: Which conduit type is required for an underground installation subject to
severe physical damage?
a) EMT
b) PVC
c) RMC
d) FMC
Correct Answer: c) RMC
Rationale: Rigid Metal Conduit (RMC) is mandated by NEC Article 344 for
underground installations exposed to severe physical damage due to its high
strength and durability. RMC protects conductors in harsh environments
better than EMT, PVC, or FMC.
Question 4: What is the minimum working clearance required in front of a 480-volt elec-
trical panel?
