CSLB C10 Electrical Exam Test 1 (2025):
100 Questions with 100% Verified Correct
Answers & Detailed Rationales
Comprehensive Study Guide for California Electrical Contractor
License Exam
Prepared for 2025 CSLB C10 Examination
July 28, 2025
,Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 Exam Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3 Study Tips for the CSLB C10 Exam . . . . . . . . . . . . . . . . . . . . . . . . . 25
4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
1
, 1 Introduction
This study guide is tailored for candidates preparing for the 2025 California State License Board
(CSLB) C10 Electrical Contractor License Exam. It includes 100 multiple-choice questions
with verified correct answers and detailed rationales, covering essential topics such as electrical
codes, safety standards, wiring methods, calculations, and equipment installation. The content
aligns with the 2022 California Electrical Code (Title 24) and focuses on clarity and relevance
to ensure efficient preparation.
2 Exam Questions and Answers
The following section contains 100 multiple-choice questions, each with four answer choices,
the correct answer, and a detailed rationale based on the National Electrical Code (NEC) and
California regulations. Questions are designed to reflect the exam’s scope, including electrical
theory, safety, and practical applications.
1. What is the minimum working clearance required in front of an electrical panel
rated at 600 V or less?
A. 24 inches
B. 30 inches
C. 36 inches
D. 42 inches
Answer: C. 36 inches
Rationale: NEC 110.26(A)(1) mandates a minimum working clearance of 36 inches in
front of electrical panels rated at 600 V or less when the opposite side is a grounded
surface. This ensures safe access for maintenance and emergency operations, reducing
the risk of electrical hazards.
2. What factors determine voltage drop in a conductor?
A. Wire material only
B. Wire gauge, length, and current flow
C. Ambient temperature and humidity
D. Insulation type
Answer: B. Wire gauge, length, and current flow
Rationale: Voltage drop is calculated using the formula V = I × R, where resistance
(R) depends on the wire’s gauge (cross-sectional area) and length, and I is the current
flow. These factors directly influence the voltage loss in a circuit, while temperature and
insulation type have secondary effects.
3. A 12-volt DC, 15-watt fluorescent light operates for 10 hours daily. How many watt-
hours are consumed daily?
A. 120 Wh
B. 150 Wh
2
100 Questions with 100% Verified Correct
Answers & Detailed Rationales
Comprehensive Study Guide for California Electrical Contractor
License Exam
Prepared for 2025 CSLB C10 Examination
July 28, 2025
,Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 Exam Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3 Study Tips for the CSLB C10 Exam . . . . . . . . . . . . . . . . . . . . . . . . . 25
4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
1
, 1 Introduction
This study guide is tailored for candidates preparing for the 2025 California State License Board
(CSLB) C10 Electrical Contractor License Exam. It includes 100 multiple-choice questions
with verified correct answers and detailed rationales, covering essential topics such as electrical
codes, safety standards, wiring methods, calculations, and equipment installation. The content
aligns with the 2022 California Electrical Code (Title 24) and focuses on clarity and relevance
to ensure efficient preparation.
2 Exam Questions and Answers
The following section contains 100 multiple-choice questions, each with four answer choices,
the correct answer, and a detailed rationale based on the National Electrical Code (NEC) and
California regulations. Questions are designed to reflect the exam’s scope, including electrical
theory, safety, and practical applications.
1. What is the minimum working clearance required in front of an electrical panel
rated at 600 V or less?
A. 24 inches
B. 30 inches
C. 36 inches
D. 42 inches
Answer: C. 36 inches
Rationale: NEC 110.26(A)(1) mandates a minimum working clearance of 36 inches in
front of electrical panels rated at 600 V or less when the opposite side is a grounded
surface. This ensures safe access for maintenance and emergency operations, reducing
the risk of electrical hazards.
2. What factors determine voltage drop in a conductor?
A. Wire material only
B. Wire gauge, length, and current flow
C. Ambient temperature and humidity
D. Insulation type
Answer: B. Wire gauge, length, and current flow
Rationale: Voltage drop is calculated using the formula V = I × R, where resistance
(R) depends on the wire’s gauge (cross-sectional area) and length, and I is the current
flow. These factors directly influence the voltage loss in a circuit, while temperature and
insulation type have secondary effects.
3. A 12-volt DC, 15-watt fluorescent light operates for 10 hours daily. How many watt-
hours are consumed daily?
A. 120 Wh
B. 150 Wh
2
