Page 1 of 49
CSLB C-10 ELECTRICAL CONTRACTOR
LICENSE EXAM-CALIFORNIA STATE
LICENSING BOARD 2026 COMPLETE (125)
CURRENT TESTING QUESTIONS AND
CORRECT ANSWERS WITH DETAILED
RATIONALES.
ELECTRICAL
Prepare for the CSLB C-10 Electrical Contractor License Exam (California
State Licensing Board) with focused review materials covering California
Electrical Code (CEC), electrical theory, residential and commercial
wiring systems, grounding and bonding, load calculations, overcurrent
protection, conduit and raceway installation, motors and transformers,
blueprint reading, estimating and bidding, project management, safety
regulations (including OSHA requirements), inspections, and California
contractor law and licensing requirements. Designed to build confidence
in interpreting plans, managing projects, applying electrical codes, and
maintaining full compliance with CSLB standards. Suitable for electrical
contractors, journeyman electricians, and candidates preparing for the
CSLB C-10 Electrical Contractor License Exam.
MULTIPLE CHOICE.
SECTION 1: ELECTRICAL THEORY & FUNDAMENTALS (Questions 1–
25)
, Page 2 of 49
1. According to Ohm's Law, if the voltage in a circuit is 240 volts and
the resistance is 30 ohms, what is the current flowing in the circuit?
A. 2 amperes
B. 8 amperes
C. 12 amperes
D. 60 amperes
Correct answer: B. 8 amperes
Rationale: Ohm's Law states that I = V/R (Current = Voltage /
Resistance). I = 240V / 30Ω = 8 amperes. Ohm's Law is the
fundamental relationship in electrical theory. The three forms are: I =
V/R, V = I × R, R = V/I.
2. A 1,500-watt, 120-volt electric heater will draw how many amperes
when operating at rated voltage?
A. 8 amperes
B. 10 amperes
C. 12.5 amperes
D. 15 amperes
Correct answer: C. 12.5 amperes
Rationale: Power (P) = Voltage (V) × Current (I). Therefore, I = P/V =
1,500W / 120V = 12.5 amperes. This is a fundamental application of
the power formula in electrical calculations.
3. Voltage drop in a wire is a function of which of the following
factors?
A. Wire gauge only
B. Length of wire only
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C. Wire gauge, length of wire, and current flow
D. The ambient temperature only
Correct answer: C. Wire gauge, length of wire, and current flow
Rationale: Voltage drop is directly influenced by the resistance of the
wire (determined by its gauge and length) and the amount of current
(amperage) flowing through it, according to Ohm's Law (V = I × R).
4. A 12-volt, 13-watt fluorescent light operates for an average of 12
hours per day. How many watt-hours does it consume daily?
A. 144 Wh
B. 1.08 Wh
C. 156 Wh
D. 1.56 Wh
Correct answer: C. 156 Wh
Rationale: Watt-hours = Watts × Hours = 13W × 12 hours = 156 watt-
hours per day.
5. What is the power consumed by a 240-volt, single-phase load
drawing 12.5 amperes?
A. 1,500 W
B. 2,400 W
C. 3,000 W
D. 4,800 W
Correct answer: C. 3,000 W
Rationale: Power = Voltage × Current = 240V × 12.5A = 3,000 watts.
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6. In a purely resistive AC circuit, what is the phase relationship
between voltage and current?
A. Voltage leads current by 90°
B. Current leads voltage by 90°
C. Voltage and current are in phase
D. Voltage leads current by 180°
Correct answer: C. Voltage and current are in phase
Rationale: In a purely resistive circuit, there is no reactive
component, so voltage and current reach their peak values
simultaneously, resulting in a zero-degree phase angle.
7. What is the total resistance of three resistors connected in parallel
with values of 10 Ω, 20 Ω, and 30 Ω?
A. 5.45 Ω
B. 10.0 Ω
C. 15.0 Ω
D. 60.0 Ω
Correct answer: A. 5.45 Ω
Rationale: For resistors in parallel, 1/R_total = 1/R₁ + 1/R₂ + 1/R₃ =
1/10 + 1/20 + 1/30 = 6/60 + 3/60 + 2/60 = 11/60. Therefore, R_total =
60/11 = 5.45 Ω.
8. A conductor has a resistance of 0.5 Ω per 1,000 feet. What is the
resistance of 2,500 feet of the same conductor?
A. 0.20 Ω
B. 0.50 Ω
C. 1.00 Ω
D. 1.25 Ω
CSLB C-10 ELECTRICAL CONTRACTOR
LICENSE EXAM-CALIFORNIA STATE
LICENSING BOARD 2026 COMPLETE (125)
CURRENT TESTING QUESTIONS AND
CORRECT ANSWERS WITH DETAILED
RATIONALES.
ELECTRICAL
Prepare for the CSLB C-10 Electrical Contractor License Exam (California
State Licensing Board) with focused review materials covering California
Electrical Code (CEC), electrical theory, residential and commercial
wiring systems, grounding and bonding, load calculations, overcurrent
protection, conduit and raceway installation, motors and transformers,
blueprint reading, estimating and bidding, project management, safety
regulations (including OSHA requirements), inspections, and California
contractor law and licensing requirements. Designed to build confidence
in interpreting plans, managing projects, applying electrical codes, and
maintaining full compliance with CSLB standards. Suitable for electrical
contractors, journeyman electricians, and candidates preparing for the
CSLB C-10 Electrical Contractor License Exam.
MULTIPLE CHOICE.
SECTION 1: ELECTRICAL THEORY & FUNDAMENTALS (Questions 1–
25)
, Page 2 of 49
1. According to Ohm's Law, if the voltage in a circuit is 240 volts and
the resistance is 30 ohms, what is the current flowing in the circuit?
A. 2 amperes
B. 8 amperes
C. 12 amperes
D. 60 amperes
Correct answer: B. 8 amperes
Rationale: Ohm's Law states that I = V/R (Current = Voltage /
Resistance). I = 240V / 30Ω = 8 amperes. Ohm's Law is the
fundamental relationship in electrical theory. The three forms are: I =
V/R, V = I × R, R = V/I.
2. A 1,500-watt, 120-volt electric heater will draw how many amperes
when operating at rated voltage?
A. 8 amperes
B. 10 amperes
C. 12.5 amperes
D. 15 amperes
Correct answer: C. 12.5 amperes
Rationale: Power (P) = Voltage (V) × Current (I). Therefore, I = P/V =
1,500W / 120V = 12.5 amperes. This is a fundamental application of
the power formula in electrical calculations.
3. Voltage drop in a wire is a function of which of the following
factors?
A. Wire gauge only
B. Length of wire only
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C. Wire gauge, length of wire, and current flow
D. The ambient temperature only
Correct answer: C. Wire gauge, length of wire, and current flow
Rationale: Voltage drop is directly influenced by the resistance of the
wire (determined by its gauge and length) and the amount of current
(amperage) flowing through it, according to Ohm's Law (V = I × R).
4. A 12-volt, 13-watt fluorescent light operates for an average of 12
hours per day. How many watt-hours does it consume daily?
A. 144 Wh
B. 1.08 Wh
C. 156 Wh
D. 1.56 Wh
Correct answer: C. 156 Wh
Rationale: Watt-hours = Watts × Hours = 13W × 12 hours = 156 watt-
hours per day.
5. What is the power consumed by a 240-volt, single-phase load
drawing 12.5 amperes?
A. 1,500 W
B. 2,400 W
C. 3,000 W
D. 4,800 W
Correct answer: C. 3,000 W
Rationale: Power = Voltage × Current = 240V × 12.5A = 3,000 watts.
, Page 4 of 49
6. In a purely resistive AC circuit, what is the phase relationship
between voltage and current?
A. Voltage leads current by 90°
B. Current leads voltage by 90°
C. Voltage and current are in phase
D. Voltage leads current by 180°
Correct answer: C. Voltage and current are in phase
Rationale: In a purely resistive circuit, there is no reactive
component, so voltage and current reach their peak values
simultaneously, resulting in a zero-degree phase angle.
7. What is the total resistance of three resistors connected in parallel
with values of 10 Ω, 20 Ω, and 30 Ω?
A. 5.45 Ω
B. 10.0 Ω
C. 15.0 Ω
D. 60.0 Ω
Correct answer: A. 5.45 Ω
Rationale: For resistors in parallel, 1/R_total = 1/R₁ + 1/R₂ + 1/R₃ =
1/10 + 1/20 + 1/30 = 6/60 + 3/60 + 2/60 = 11/60. Therefore, R_total =
60/11 = 5.45 Ω.
8. A conductor has a resistance of 0.5 Ω per 1,000 feet. What is the
resistance of 2,500 feet of the same conductor?
A. 0.20 Ω
B. 0.50 Ω
C. 1.00 Ω
D. 1.25 Ω
