CSLB C10 Electrical Exam Test 1
(2025): 100 Questions with 100%
Verified Correct Answers & Detailed
Rationales Prepared for Aspiring Electrical Contractors
Updated: July 2025
,Contents
1 Introduction 2
2 Practice Test Questions and Answers 2
3 Conclusion 17
1
, 1 Introduction
This document provides a comprehensive practice test for the CSLB C10 Electrical Con-
tractor License Exam for 2025. It includes 100 carefully curated questions with verified
correct answers and detailed rationales to enhance understanding of key electrical con-
cepts. The questions cover essential topics such as electrical theory, National Electrical
Code (NEC) compliance, safety practices, wiring methods, and equipment installation,
tailored to reflect the exam’s scope and rigor.
2 Practice Test Questions and Answers
Question 1
What is the minimum size of a grounding electrode conductor for a 200A
service using copper conductors?
A: 4 AWG
Rationale: According to NEC Table 250.66, for a 200A service with copper conductors,
the minimum grounding electrode conductor size is 4 AWG copper. This size ensures the
conductor can safely carry fault current to ground, protecting equipment and personnel.
Question 2
What is the maximum allowable voltage drop for a branch circuit supplying
a residential lighting load?
A: 3%
Rationale: NEC 210.19(A)(1) Informational Note No. 4 recommends a maximum volt-
age drop of 3% for branch circuits to ensure efficient operation of lighting loads. This
minimizes energy loss and maintains adequate voltage for proper performance.
Question 3
What type of conduit is required for an underground installation in a corro-
sive environment?
A: Rigid PVC
Rationale: NEC 352.10 permits rigid PVC conduit for underground installations in cor-
rosive environments due to its resistance to chemical degradation and moisture, ensuring
durability and safety.
Question 4
How many 12 AWG conductors can be installed in a 3/4-inch EMT conduit?
A: 16
Rationale: NEC Annex C, Table C.1, specifies that a 3/4-inch EMT conduit can ac-
commodate up to 16 conductors of 12 AWG THHN/THWN, based on a 40% conduit fill
limit, ensuring compliance with thermal and physical constraints.
Question 5
2
(2025): 100 Questions with 100%
Verified Correct Answers & Detailed
Rationales Prepared for Aspiring Electrical Contractors
Updated: July 2025
,Contents
1 Introduction 2
2 Practice Test Questions and Answers 2
3 Conclusion 17
1
, 1 Introduction
This document provides a comprehensive practice test for the CSLB C10 Electrical Con-
tractor License Exam for 2025. It includes 100 carefully curated questions with verified
correct answers and detailed rationales to enhance understanding of key electrical con-
cepts. The questions cover essential topics such as electrical theory, National Electrical
Code (NEC) compliance, safety practices, wiring methods, and equipment installation,
tailored to reflect the exam’s scope and rigor.
2 Practice Test Questions and Answers
Question 1
What is the minimum size of a grounding electrode conductor for a 200A
service using copper conductors?
A: 4 AWG
Rationale: According to NEC Table 250.66, for a 200A service with copper conductors,
the minimum grounding electrode conductor size is 4 AWG copper. This size ensures the
conductor can safely carry fault current to ground, protecting equipment and personnel.
Question 2
What is the maximum allowable voltage drop for a branch circuit supplying
a residential lighting load?
A: 3%
Rationale: NEC 210.19(A)(1) Informational Note No. 4 recommends a maximum volt-
age drop of 3% for branch circuits to ensure efficient operation of lighting loads. This
minimizes energy loss and maintains adequate voltage for proper performance.
Question 3
What type of conduit is required for an underground installation in a corro-
sive environment?
A: Rigid PVC
Rationale: NEC 352.10 permits rigid PVC conduit for underground installations in cor-
rosive environments due to its resistance to chemical degradation and moisture, ensuring
durability and safety.
Question 4
How many 12 AWG conductors can be installed in a 3/4-inch EMT conduit?
A: 16
Rationale: NEC Annex C, Table C.1, specifies that a 3/4-inch EMT conduit can ac-
commodate up to 16 conductors of 12 AWG THHN/THWN, based on a 40% conduit fill
limit, ensuring compliance with thermal and physical constraints.
Question 5
2
