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Practice Exam
Question 1. Which article of the NEC defines the term “grounded conductor”? A) Article 100 B) Article 250 C) Article 300 D) Article 210 Answer: A Explanation: Article 100 provides definitions for NEC terminology, including “grounded conductor,” which is the conductor that is intentionally connected to ground (normally the neutral). Question 2. According to NEC 210.52(A)(1), the spacing between receptacles in a dwelling unit living area shall not exceed: A) 4 ft B) 6 ft C) 8 ft D) 12 ft Answer: B Explanation: NEC 210.52(A)(1) requires receptacles to be installed so that no point along the wall line is more than 6 ft from a receptacle. Question 3. In a three‑phase, four‑wire wye system, the line‑to‑neutral voltage is 120 V. What is the line‑to‑line voltage? A) 120 V B) 208 V C) 240 V D) 277 V
Practice Exam
Answer: B Explanation: Line‑to‑line voltage = √ 3 × line‑to‑neutral. √ 3 × 120 V ≈ 208 V. Question 4. Which NEC article governs the installation of ground‑fault circuit‑interrupters (GFCIs) in residential bathrooms? A) Article 210 B) Article 210.8(A)(1) C) Article 250. D) Article 300. Answer: B Explanation: NEC 210.8(A)(1) specifically requires GFCI protection for receptacles in bathrooms of dwellings. Question 5. A feeder supplying a 100 A panelboard is installed with 4/0 AWG copper conductors. According to NEC Table 310.15(B)(16), what is the allowable ampacity of this conductor in a 75 °C column? A) 85 A B) 100 A C) 125 A D) 150 A Answer: C Explanation: 4/0 AWG copper has an ampacity of 125 A at 75 °C per Table 310.15(B)(16). Question 6. When calculating voltage drop for a 120 V branch circuit 150 ft long with a 15 A load, which formula is appropriate? A) Vdrop = I × R × 2
Practice Exam
Question 9. Which NEC article addresses the grounding electrode system for a building? A) Article 250. B) Article 250. C) Article 250. D) Article 250. Answer: B Explanation: Article 250.52 specifies the types of grounding electrodes and the requirements for their installation. Question 10. For a 30 kW, 480 V, three‑phase motor, what is the approximate full‑load current (FLC) using NEC Table 430.250? A) 35 A B) 45 A C) 55 A D) 70 A Answer: B Explanation: Table 430.250 shows an FLC of about 45 A for a 30 kW, 480 V, three‑phase motor. Question 11. Which of the following conduit types allows a maximum of 10 bends between pull points? A) Rigid Metal Conduit (RMC) B) Electrical Metallic Tubing (EMT) C) Flexible Metal Conduit (FMC) D) PVC Schedule 40
Practice Exam
Answer: B Explanation: NEC 358.30 permits up to 10 90‑degree bends (or the equivalent) in EMT between pull points. Question 12. In a dwelling unit, the required minimum number of receptacles in a kitchen countertop space is: A) One per 12 in. of countertop length B) One per 24 in. of countertop length C) One per 36 in. of countertop length D) One per 48 in. of countertop length Answer: B Explanation: NEC 210.52(C) requires at least one receptacle per 24 in. of countertop space. Question 13. Which NEC article governs the installation of fuel‑cell power systems? A) Article 690 B) Article 706 C) Article 700 D) Article 625 Answer: D Explanation: Article 625 covers the installation of fuel‑cell power systems, including safety and grounding requirements. Question 14. A grounding electrode conductor (GEC) of #6 AWG copper is required for a grounding electrode that is a concrete‑encased electrode. According to NEC 250.66, this size is based on: A) The size of the service‑entrance conductors
Practice Exam
Question 17. Which NEC article specifies the requirements for installing wiring in hazardous (classified) locations? A) Article 500 B) Article 300 C) Article 210 D) Article 430 Answer: A Explanation: Article 500 covers classification, installation, and equipment requirements for hazardous locations. Question 18. The minimum size of an equipment grounding conductor (EGC) for a 20‑A, 120‑V branch circuit using copper conductors with 75 °C insulation is: A) #14 AWG B) #12 AWG C) #10 AWG D) #8 AWG Answer: B Explanation: Table 250.122 requires a #12 AWG copper EGC for a 20‑A circuit. Question 19. For a 120‑V, 15‑A receptacle in a dwelling unit, the maximum distance from the outlet to the nearest point on the floor is: A) 12 in. B) 18 in. C) 24 in.
Practice Exam
D) No limit specified Answer: D Explanation: NEC does not limit the vertical distance from the receptacle to the floor; the limitation is on horizontal spacing (6 ft). Question 20. Which of the following is NOT a permissible use for Type NM‑B cable? A) Inside walls of a dwelling unit B) In a wet location C) For feeder circuits in a residential garage D) For branch circuits in a finished basement Answer: B Explanation: Type NM‑B (non‑metallic sheathed) cable is prohibited in wet locations per NEC 334.10. Question 21. A 240‑V, 30 A dryer circuit requires a minimum conductor size of: A) #12 AWG copper B) #10 AWG copper C) #8 AWG copper D) #6 AWG copper Answer: B Explanation: NEC Table 310.15(B)(16) shows #10 AWG copper is rated for 30 A at 60 °C, which is the required size for a dryer circuit. Question 22. Which NEC article requires that all receptacles in a garage be GFCI protected? A) Article 210.8(A)(2) B) Article 210.12(A)
Practice Exam
Question 25. Which of the following devices provides protection against both ground‑fault and over‑current conditions? A) GFCI receptacle B) AFCI circuit breaker C) Standard circuit breaker with ground‑fault detection D) No single device provides both; separate devices are required Answer: D Explanation: GFCI provides ground‑fault protection only; over‑current protection requires a circuit breaker or fuse. They are separate devices. Question 26. The minimum clearance required between a 120‑V receptacle and a bathtub edge is: A) 12 in. B) 18 in. C) 24 in. D) 30 in. Answer: C Explanation: NEC 210.8(A)(10) requires receptacles within 3 ft of a bathtub to be GFCI protected; clearance for installation is 24 in. from the tub edge. Question 27. In a commercial kitchen, the required ampacity for a 20‑A branch circuit supplying a countertop receptacle is: A) 16 A B) 20 A C) 24 A (125 % of load) D) 30 A
Practice Exam
Answer: C Explanation: NEC 210.23(A)(2) requires a 125 % factor for receptacle loads in commercial kitchens, so a 20 ‑A circuit must be rated for 24 A. Question 28. Which NEC article governs the installation of photovoltaic (PV) systems? A) Article 690 B) Article 706 C) Article 700 D) Article 620 Answer: A Explanation: Article 690 contains the requirements for the installation, wiring, and grounding of solar photovoltaic systems. Question 29. For a solid‑core copper conductor with 75 °C insulation used in a conduit, the ampacity must be adjusted for: A) Ambient temperature only B) Number of conductors in the raceway only C) Both ambient temperature and number of conductors D) No adjustment is required Answer: C Explanation: NEC Table 310.15(B)(2)(a) provides temperature correction factors, and Table 310.15(B)(3)(a) provides derating for more than three current‑carrying conductors. Question 30. Which of the following is the correct method to size a feeder for a 200 kVA, 480 V, three‑phase load with a demand factor of 0.8? A) Use 200 kVA ÷ (√3 × 480) × 0.8 to find current, then select conductor
Practice Exam
Question 33. Which of the following is a permissible use for a 3‑wire (hot‑hot‑neutral) NM cable in a residential branch circuit? A) Supplying a 240‑V appliance with no neutral required B) Supplying a 120‑V lighting circuit with a neutral C) Supplying a 120/240‑V dryer circuit requiring a neutral D) Supplying a 120‑V receptacle in a kitchen Answer: A Explanation: A 3‑wire NM (hot‑hot‑neutral) can be used for a 240‑V circuit that does not require a neutral, such as a water heater. Question 34. According to NEC 210.11(C)(1), the minimum number of required 20‑A small‑appliance branch circuits for a dwelling unit is: A) One B) Two C) Three D) Four Answer: B Explanation: NEC 210.11(C)(1) mandates at least two 20‑A small‑appliance branch circuits for the kitchen, pantry, and dining areas. Question 35. In a fire alarm system, the power supply must be installed in accordance with which NEC article? A) Article 760 B) Article 700 C) Article 725
Practice Exam
D) Article 645 Answer: A Explanation: Article 760 covers fire alarm systems, including power supply and wiring requirements. Question 36. A grounding electrode conductor (GEC) must be protected against physical damage. Which method is acceptable? A) Run the GEC inside a metal conduit only B) Bury the GEC directly in earth without protection C) Use a listed GEC with a protective sleeve where exposed D) No protection is required for GECs Answer: C Explanation: NEC 250.64(A) allows a listed GEC to be protected with a sleeve or conduit where it is exposed to physical damage. Question 37. Which NEC article addresses the installation of emergency lighting systems? A) Article 700 B) Article 701 C) Article 702 D) Article 760 Answer: A Explanation: Article 700 covers emergency systems, including emergency lighting and power. Question 38. For a 120‑V, 20‑A dedicated circuit feeding an electric range, the required conductor size (copper) is: A) #12 AWG
Practice Exam
Question 41. Which NEC article governs the requirements for wiring in swimming pools and related equipment? A) Article 680 B) Article 690 C) Article 500 D) Article 645 Answer: A Explanation: Article 680 addresses swimming pools, hot tubs, and fountains, including wiring, bonding, and GFCI protection. Question 42. The permissible voltage drop for feeder conductors supplying a continuous load is limited to: A) 1 % B) 2 % C) 3 % D) 5 % Answer: C Explanation: NEC 210.19(A)(1) recommends a maximum of 3 % voltage drop for feeders (combined with branch circuits not exceeding 5 % total). Question 43. In a commercial building, the lighting load is calculated using the demand factor of 100 % for the first 3 kW and 35 % for the remainder. If the total calculated lighting load is 10 kW, what is the demand‑factor‑adjusted load? A) 3 kW + (7 kW × 0.35) = 5.45 kW B) 10 kW × 0.35 = 3.5 kW
Practice Exam
C) 3 kW + (7 kW × 0.5) = 6.5 kW D) 10 kW × 0.5 = 5 kW Answer: A Explanation: NEC Table 220.42 uses 100 % for the first 3 kW, then 35 % for the remaining 7 kW: 3 kW + (7 kW × 0.35) = 5.45 kW. Question 44. Which of the following is NOT a permitted location for a receptacle in a bathroom according to NEC? A) Within the tub wall B) At least 3 ft from the tub edge C) At least 18 in. above the tub rim D) At any height, provided it is GFCI protected Answer: A Explanation: NEC 210.8(A)(1) prohibits receptacles from being installed inside a tub or shower enclosure. Question 45. For a 120/240‑V, single‑phase service, the maximum allowable neutral‑to‑ground voltage under normal conditions is: A) 2 V B) 5 V C) 10 V D) No limit specified Answer: B Explanation: NEC 250.24(C) limits the neutral‑to‑ground voltage to 5 V under normal operating conditions.
Practice Exam
Answer: A Explanation: Article 445 covers generators, including installation, grounding, and disconnecting means. Question 49. A receptacle installed in a residential garage must be GFCI protected. Which NEC provision establishes this requirement? A) 210.8(A)(2) B) 210.12(A) C) 250.68(A) D) 300.4(B) Answer: A Explanation: NEC 210.8(A)(2) requires GFCI protection for all receptacles in garages of dwellings. Question 50. For a 3‑phase, 480‑V motor with a full‑load current of 50 A, the minimum size of the overload protection device is: A) 50 A B) 55 A C) 60 A D) 75 A Answer: C Explanation: NEC 430.32 requires overload protection to be set at 115 % of the motor FLC: 50 A × 1.15 = 57.5 A, rounded up to the next standard size, 60 A. Question 51. Which of the following is the correct conductor color code for a 120/240‑V single‑phase system in the United States? A) Black – hot, White – neutral, Green – ground
Practice Exam
B) Red – hot, Black – neutral, Green – ground C) Blue – hot, White – neutral, Red – ground D) Brown – hot, Black – neutral, Yellow – ground Answer: A Explanation: Standard U.S. color coding: black (or red) for hot, white for neutral, green (or bare) for equipment grounding. Question 52. According to NEC 210.2(A), the minimum ampacity of a branch‑circuit conductor supplying a single receptacle must be: A) 15 A for 15‑A receptacle, 20 A for 20‑A receptacle B) 125 % of the receptacle rating C) 150 % of the receptacle rating D) No minimum; any size may be used Answer: A Explanation: NEC 210.2(A) requires that the branch‑circuit conductor be rated at least as large as the receptacle’s rating (15 A or 20 A). Question 53. A 120/240‑V, single‑phase service is supplied by a 4/0 AWG aluminum feeder. What is the minimum size of the grounding electrode conductor required? A) #8 AWG copper B) #6 AWG copper C) #4 AWG copper D) #2 AWG copper Answer: C Explanation: NEC 250.66 requires the GEC to be sized based on the largest ungrounded service conductor; for 4/0 AWG Al, the equivalent copper size is #4 AWG.
