California C-10 Electrical Contractor Exam 2025 – Questions & Answers with Rationales | 100% Verified | Graded A+

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‭ alifornia C-10 Electrical Contractor Exam 2025‬
C
‭– Questions & Answers with Rationales | 100%‬
‭Verified | Graded A+‬
‭Student Name:‬‭_________________________‬‭Date:‬‭_______________‬
‭Time Limit‬‭:‬‭150 minutes‬‭Total Question‬‭s:‬‭115‬


‭Instructions‬
‭●‬ T ‭ his exam simulates the California C-10 Electrical Contractor License Exam based on 2025‬
‭CSLB requirements and NEC 2023 standards.‬
‭●‬ ‭Answer all questions by selecting the correct option. Correct answers.‬
‭●‬ ‭Rationales are provide for each question to explain the correct answer.‬
‭●‬ ‭Ensure compliance with NEC 2023 and California-specific regulations.‬




‭National Electrical Code (NEC 2023 Updates)‬
‭1.‬ A
‭ ccording to NEC 2023, what is the minimum size copper equipment grounding conductor‬
‭required for a 200A feeder circuit?‬
‭a. 8 AWG‬
‭b. 6 AWG‬
‭c. 4 AWG‬
‭d. 2 AWG‬
‭Answer: b. 6 AWG‬
‭Rationale: Per NEC 2023 Table 250.122, a 200A feeder requires a 6 AWG copper equipment‬
‭grounding conductor to ensure proper fault current path.‬

‭2.‬ W
‭ hat is the maximum allowable ampacity for a 10 AWG THHN copper conductor in a raceway‬
‭with three current-carrying conductors at 30°C ambient temperature?‬
‭a. 30 A‬
‭b. 35 A‬
‭c. 40 A‬
‭d. 50 A‬
‭Answer: b. 35 A‬

, ‭2‬


‭ ationale: NEC 2023 Table 310.16 lists 10 AWG THHN copper at 40 A for 90°C. No adjustment‬
R
‭is needed for three conductors or 30°C ambient, but the terminal rating limits it to 35 A (75°C‬
‭column).‬

‭3.‬ A
‭ branch circuit supplying a 120V, 15A receptacle in a dwelling unit kitchen must comply with‬
‭which NEC 2023 requirement?‬
‭a. GFCI protection‬
‭b. AFCI protection‬
‭c. Both GFCI and AFCI protection‬
‭d. No special protection required‬
‭Answer: c. Both GFCI and AFCI protection‬
‭Rationale: NEC 2023 Section 210.8(A) requires GFCI protection for kitchen receptacles, and‬
‭Section 210.12 requires AFCI protection for 120V, 15A, and 20A branch circuits in dwelling unit‬
‭kitchens.‬

‭4.‬ P
‭ er NEC 2023, what is the minimum clearance required in front of a 480V panelboard?‬
‭a. 2 feet‬
‭b. 3 feet‬
‭c. 4 feet‬
‭d. 5 feet‬
‭Answer: b. 3 feet‬
‭Rationale: NEC 2023 Section 110.26(A) requires a minimum of 3 feet of clear working space in‬
‭front of electrical equipment operating at 600V or less.‬

‭5.‬ W
‭ hat is the maximum number of disconnects allowed for a single service entrance per NEC‬
‭2023?‬
‭a. 4‬
‭b. 6‬
‭c. 8‬
‭d. 10‬
‭Answer: b. 6‬
‭Rationale: NEC 2023 Section 230.71 allows up to six disconnects for a single service entrance to‬
‭ensure safe and manageable service isolation.‬

‭6.‬ A
‭ new requirement in NEC 2023 for surge protection applies to which type of installation?‬
‭a. All dwelling units‬
‭b. Commercial buildings only‬
‭c. Services supplying life safety systems‬
‭d. Industrial facilities only‬
‭Answer: a. All dwelling units‬
‭Rationale: NEC 2023 Section 230.67 requires surge protective devices (SPDs) for all dwelling‬
‭unit services to protect against voltage surges.‬

, ‭3‬


‭7.‬ W
‭ hat is the minimum size of a grounding electrode conductor for a 400A service using copper?‬
‭a. 4 AWG‬
‭b. 2 AWG‬
‭c. 1/0 AWG‬
‭d. 2/0 AWG‬
‭Answer: c. 1/0 AWG‬
‭Rationale: NEC 2023 Table 250.66 specifies a 1/0 AWG copper grounding electrode conductor‬
‭for a 400A service.‬

‭8.‬ P
‭ er NEC 2023, which type of cable is permitted for direct burial without a conduit in a residential‬
‭application?‬
‭a. NM-B‬
‭b. UF-B‬
‭c. THHN‬
‭d. MC‬
‭Answer: b. UF-B‬
‭Rationale: NEC 2023 Section 334.10 prohibits NM-B for direct burial, but Section 340.10 allows‬
‭UF-B cable for direct burial due to its moisture-resistant construction.‬

‭9.‬ W
‭ hat is the required ampacity adjustment factor for six current-carrying conductors in a single‬
‭conduit at 30°C?‬
‭a. 0.7‬
‭b. 0.8‬
‭c. 0.9‬
‭d. 1.0‬
‭Answer: b. 0.8‬
‭Rationale: NEC 2023 Table 310.15(B)(3)(a) specifies an 80% adjustment factor (0.8) for 4–6‬
‭current-carrying conductors in a single raceway.‬

‭10.‬ ‭For a 240V single-phase circuit, what is the minimum size copper conductor for a 50A load?‬
‭a. 10 AWG‬
‭b. 8 AWG‬
‭c. 6 AWG‬
‭d. 4 AWG‬
‭Answer: c. 6 AWG‬
‭Rationale: NEC 2023 Table 310.16 specifies 6 AWG copper THHN (75°C column) for a 50A‬
‭load, rated at 55 A.‬



‭Grounding, Bonding & Conduit Fill‬
‭11.‬ ‭What is the purpose of bonding per NEC 2023?‬
‭a. To reduce voltage drop‬
‭b. To ensure a continuous fault current path‬