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Question 1. In a single-phase AC circuit, the total impedance is 50 Ω and the supply voltage is 120 V rms. What is the current flowing in the circuit? A) 1.2 A B) 2.4 A C) 3.0 A D) 4.8 A Answer: B Explanation: Ohm’s law for AC is I = V/Z = 120 V / 50 Ω = 2.4 A. Question 2. A 150 kW, 460 V three-phase motor is connected in a Wye. What is the line current? A) 188 A B) 215 A C) 236 A D) 267 A Answer: A Explanation: Power = √3 × V_L × I_L × PF. Assuming PF ≈ 1, I = P/(√3 V) = 150 000 W/(1.732 × 460 V) ≈ 188 A. Question 3. Which NEC article governs the requirements for grounding electrode conductors? A) 210 B) 250 C) 300 D) 410 Answer: B Explanation: Article 250 of the NEC deals with grounding and bonding, including the grounding electrode conductor.
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Question 4. A 12-AWG copper conductor is installed in a conduit with three current-carrying conductors in an ambient temperature of 40 °C. What is the adjusted ampacity? A) 20 A B) 25 A C) 30 A D) 35 A Answer: B Explanation: 12-AWG copper rated 30 A at 30 °C. Derating for three conductors is 80 % (NEC Table 310.15(B)(3)(a)). 30 A × 0.80 = 24 A, rounded up to the next standard size → 25 A. Question 5. Which of the following devices provides protection against both ground-fault and arc-fault conditions? A) GFCI breaker B) AFCI breaker C) Dual-function GFCI/AFCI breaker D) Standard circuit breaker Answer: C Explanation: Dual-function breakers combine ground-fault and arc-fault protection in a single device. Question 6. In a residential branch circuit, how many receptacles are allowed on a 20-A circuit that supplies only lighting loads? A) Unlimited B) 10 C) 12 D) 14 Answer: A Explanation: NEC permits an unlimited number of lighting outlets on a branch circuit; the limitation applies to receptacles (15-A circuits limited to 12, 20-A to 13). Lighting loads are not limited.
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Question 10. In a Class I, Division 2 hazardous location, which wiring method is permitted for power conductors? A) NM-B cable B) MC cable with interlocking metal boxes C) PVC conduit with THHN conductors D) Rigid metal conduit (RMC) only Answer: C Explanation: PVC conduit (non-metallic) is allowed in Class I, Division 2 areas for power conductors, provided the conductors are rated for the environment. Question 11. How many conductors are permitted in a standard 1-in. EMT conduit with a 40 % fill limit? A) 3 #12 THHN B) 5 #10 THHN C) 7 #14 THHN D) 9 #12 THHN Answer: A Explanation: The internal area of 1-in. EMT is 0.864 in². A #12 THHN has an area of 0.0133 in². 40 % fill = 0.3456 in². 0.3456 / 0.0133 ≈ 26 conductors, but the NEC limits to a maximum of 3 conductors for more than 2 conductors in a raceway. Thus 3 # THHN is permissible. Question 12. Which NEC article governs the installation of receptacles in a bathroom? A) 210.8(A)(1) B) 210.8(A)(2) C) 210.8(A)(3) D) 210.8(A)(4) Answer: A Explanation: Article 210.8(A)(1) requires GFCI protection for receptacles installed in bathrooms.
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Question 13. A transformer has a primary voltage of 13.2 kV and a secondary voltage of 480 V. What is the turns ratio? A) 27.5: B) 20: C) 15: D) 10: Answer: A Explanation: Turns ratio = V_primary / V_secondary = 13 200 V / 480 V ≈ 27.5 : 1. Question 14. For a 120/240-V single-phase service, what is the maximum number of disconnecting means allowed in the service equipment? A) 1 B) 2 C) 3 D) Unlimited Answer: B Explanation: NEC 230.71 permits a maximum of two disconnecting means for a single-phase, 3-wire service. Question 15. Which of the following is the correct box-fill calculation for a device (switch or receptacle) with a yoke? A) One conductor volume B) Two conductor volumes C) Three conductor volumes D) Four conductor volumes Answer: C Explanation: NEC 314.16(B) states that a yoke containing a single device counts as three conductors toward box fill. Question 16. A 30-A GFCI circuit breaker is installed to protect a 120-V kitchen countertop receptacle. What is the minimum rating of the receptacle?
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C) 65 %
D) 60 %
Answer: B Explanation: For 4-6 conductors, the factor is 80 %; however at 35 °C (above 30 °C) an additional temperature correction of 0.88 is applied, resulting in 0.80 × 0.88 ≈ 70 %. Question 20. Which type of conduit is required for a direct-buried installation of a feeder in a residential driveway? A) EMT B) RMC C) PVC conduit (Schedule 40) D) Flexible metal conduit (FMC) Answer: C Explanation: Direct-buried conductors must be in a raceway suitable for burial; PVC Schedule 40 is listed for direct burial. Question 21. What is the minimum ampere rating for a feeder supplying a 6 kW, 240 - V, single-phase air-conditioning unit? A) 15 A B) 20 A C) 25 A D) 30 A Answer: B Explanation: Current = P/V = 6000 W / 240 V = 25 A. Applying a 125 % demand factor for continuous loads gives 31.25 A, thus the next standard size is 35 A. However, the question asks for minimum rating before demand factor, which is 25 A; the nearest standard size is 30 A, but 20 A would be insufficient. The correct answer is C 25 A, but since 25 A is not a standard size, the next standard is D 30 A. Correct answer: D. Question 22. Which NEC article governs the installation of receptacles in a swimming pool?
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A) 680
B) 690
C) 695
D) 698
Answer: A Explanation: Article 680 covers swimming pools, fountains, and similar installations, including receptacle requirements. Question 23. In a commercial building, a fire-pump motor requires a dedicated feeder. Which article specifies the required overcurrent protection for the pump? A) 430 B) 440 C) 450 D) 460 Answer: B Explanation: Article 440 deals with air-conditioning and refrigerating equipment, including fire-pump motors. Question 24. How many grounding-electrode conductors (GEC) are required for a residential service with a concrete-encased electrode and a metal water pipe? A) One, sized for the larger of the two B) One for each electrode, sized individually C) Two, tied together at the service equipment D) No GEC is required if the water pipe is metallic Answer: C Explanation: NEC 250.53(A)(2) requires each grounding electrode to be bonded to the grounding electrode system, typically by connecting each GEC to the service grounding bus. Question 25. Which of the following is the correct NEC reference for the required working clearances in front of electrical equipment?
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A) 115 % of full-load current B) 125 % of full-load current C) 135 % of full-load current D) 150 % of full-load current Answer: B Explanation: NEC 430.32 allows overload protection set at 115 %–125 % of the motor’s full-load current. The typical setting for a 30-HP motor is 125 %. Question 29. Which NEC article defines the requirements for conduit fill in raceways? A) 300. B) 310. C) 314. D) 378. Answer: C Explanation: Article 314.16 provides the calculations for box and conduit fill. Question 30. For a 3-phase, 4-wire Wye system, the neutral conductor must be sized at least what proportion of the ungrounded conductor? A) 50 % B) 75 % C) 100 % D) 125 % Answer: C Explanation: NEC 220.61 requires the neutral to be sized equal to the maximum unbalanced load, which is often taken as 100 % of the largest ungrounded conductor when the load is not known. Question 31. Which NEC article addresses the installation of wiring in health-care facilities? A) 517
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B) 518
C) 519
D) 520
Answer: A Explanation: Article 517 contains the specific requirements for health-care facilities. Question 32. A 12-kV service entrance requires a grounding electrode conductor of what size? A) 4 AWG copper B) 2 AWG copper C) 1/0 AWG copper D) 2/0 AWG copper Answer: C Explanation: Table 250.66 requires 1/0 AWG copper for services of 100 A to 400 A; for a 12-kV service this size is appropriate. Question 33. Which of the following is NOT a permitted method for grounding a metal conduit system? A) Using a grounding screw at each box B) Installing a grounding electrode conductor inside the conduit C) Relying on the conduit’s metallic armor alone D) Bonding the conduit to the service equipment grounding bar Answer: C Explanation: Metallic conduit can serve as an equipment grounding conductor only if it is continuous and properly bonded; relying solely on the armor without bonding is not permitted. Question 34. In a Class II, Division 1 hazardous location, which type of cable is acceptable for power distribution? A) NM-B B) MC with interlocking metal fittings
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Answer: B Explanation: The feeder must be protected at or above the load current; a 20 A breaker matches the circuit’s rating. Question 38. Which of the following is the correct NEC reference for the required spacing of receptacles in a dwelling kitchen countertop? A) 210.52(C)(1) B) 210.52(D)(1) C) 210.52(E)(1) D) 210.52(F)(1) Answer: A Explanation: NEC 210.52(C)(1) specifies receptacle spacing in kitchen countertops. Question 39. For a 3-wire, 120/240-V service, the neutral conductor must be protected against which condition? A) Overcurrent only B) Overvoltage only C) Both overcurrent and overvoltage D) No protection required Answer: A Explanation: The neutral must be protected against overcurrent per NEC 250.122, but not overvoltage. Question 40. Which NEC article defines the requirements for emergency power systems? A) 700 B) 701 C) 702 D) 703 Answer: A
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Explanation: Article 700 covers emergency systems, including power sources and transfer equipment. Question 41. A conduit run is installed in a wet location. Which of the following conduit types is NOT permitted? A) EMT B) RMC C) PVC D) Flexible metal conduit (FMC) with liquid-tight coating Answer: A Explanation: EMT is not rated for wet locations; RMC, PVC, and liquid-tight FMC are permissible. Question 42. What is the maximum number of conductors allowed in a 3/4-in. PVC conduit for a 40 % fill? A) 5 B) 7 C) 9 D) 11 Answer: B Explanation: The internal area of 3/4-in. PVC conduit is 0.533 in². 40 % fill = 0.213 in². A #12 THHN (0.0133 in²) allows 0.213 / 0.0133 ≈ 16 conductors, but NEC limits to a maximum of 9 conductors for more than 2 conductors. Therefore, 7 is a safe typical answer; however, the exact answer may vary. Correct answer: B. Question 43. Which NEC article governs the installation of wiring methods for fire-pump systems? A) 430 B) 440 C) 450 D) 460 Answer: B
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Question 47. Which NEC article addresses the requirements for box fill in luminaire (fixture) installations? A) 410 B) 314 C) 300 D) 250 Answer: B Explanation: Box-fill requirements are in Article 314, covering all enclosures including luminaires. Question 48. In a commercial building, a receptacle is required to be GFCI protected because it is installed in a… A) Dry storage room B) Office space C) Laundry area D) Hallway Answer: C Explanation: NEC 210.8(A)(6) mandates GFCI protection for receptacles in laundry areas. Question 49. Which of the following devices is required for a feeder supplying a panelboard that serves a hazardous (Class I) location? A) Standard circuit breaker B) GFCI breaker C) Explosion-proof enclosure D) Listed conduit only Answer: C Explanation: Equipment serving Class I hazardous locations must be listed for explosion protection.
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Question 50. What is the minimum size of a grounding electrode conductor required for a 400 A service? A) 2 AWG copper B) 4 AWG copper C) 2/0 AWG copper D) 4/0 AWG copper Answer: C Explanation: Table 250.66 calls for 2/0 AWG copper for services 400 A to 600 A. Question 51. Which NEC article specifies the requirements for the installation of cable trays? A) 320 B) 392 C) 380 D) 378 Answer: D Explanation: Article 378 covers the installation of cable trays. Question 52. A 250-V, 30-A branch circuit must be protected by a breaker sized at… A) 25 A B) 30 A C) 35 A D) 40 A Answer: B Explanation: The breaker must be rated equal to or greater than the circuit’s ampacity; 30 A is appropriate. Question 53. Which NEC article deals with the installation of wiring in swimming pool decks? A) 680
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B) AFCI only C) Both GFCI and AFCI D) No special protection required Answer: A Explanation: NEC 210.8(A)(10) requires GFCI protection for receptacles installed within 6 ft of a bathtub. Question 57. Which NEC article defines the requirements for the installation of conduit in non-metallic raceways? A) 352 B) 358 C) 376 D) 380 Answer: B Explanation: Article 358 covers electrical non-metallic raceways (PVC). Question 58. For a 60 A, 240 V single-phase feeder, what is the minimum size copper conductor? A) 6 AWG B) 8 AWG C) 10 AWG D) 12 AWG Answer: B Explanation: Table 310.15(B)(16) shows 8 AWG copper rated for 55 A at 75 °C, but using 90 °C rating (70 A) and applying appropriate derating permits 60 A. Question 59. Which of the following is the correct NEC reference for the required disconnecting means for a motor? A) 430. B) 430. C) 430.
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D) 430.
Answer: A Explanation: Article 430.102 requires a disconnecting means within sight of the motor. Question 60. A 30-A, 120/240-V single-phase dryer circuit requires a neutral conductor. What size neutral is required? A) 12 AWG copper B) 10 AWG copper C) 8 AWG copper D) 6 AWG copper Answer: B Explanation: NEC 220.61 permits the neutral to be sized at 150 % of the unbalanced load; a 10 AWG copper (30 A) is appropriate. Question 61. Which NEC article governs the installation of wiring for elevators? A) 600 B) 620 C) 630 D) 640 Answer: B Explanation: Article 620 covers elevators and escalators. Question 62. The minimum required rating for a grounding electrode conductor attached to a 200-A service is… A) 6 AWG copper B) 8 AWG copper C) 4 AWG copper D) 2 AWG copper Answer: B
