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Exam Guide
Question 1. Which NEC article defines “accessible” and “readily accessible”? A) Article 100 B) Article 110 C) Article 210 D) Article 250 Answer: A Explanation: Article 100 contains definitions of terms used throughout the NEC, including “accessible” and “readily accessible.” Question 2. In a three-phase, 4-wire wye system, the neutral conductor carries the unbalanced current. What is the maximum allowable neutral ampacity relative to the phase conductors? A) 50 % of phase ampacity B) 100 % of phase ampacity C) 150 % of phase ampacity D) 200 % of phase ampacity Answer: B Explanation: NEC permits the neutral to be sized at the same ampacity as the phase conductors for balanced or unbalanced loads. Question 3. A residential service has a calculated load of 42 kVA. Using a 120/240-V single-phase system, what minimum size (in amperes) of the service-entrance overcurrent protective device (OCPD) is required? A) 100 A B) 125 A C) 150 A D) 200 A
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Answer: B Explanation: 42 kVA ÷ 240 V = 175 A. NEC requires rounding up to the next standard breaker size; 125 A is insufficient, so the next standard size is 150 A, but the load calculation includes demand factors that typically reduce the required size to 125 A for a typical dwelling. Question 4. When sizing service-entrance conductors, which factor must be applied for a conductor installed in a raceway exposed to ambient temperatures of 40 °C (104 °F) when the NEC table assumes 30 °C (86 °F)? A) 0. B) 0. C) 1. D) 1. Answer: B Explanation: NEC Table 310.15(B)(1) provides temperature correction factors; at 40 °C the factor for THHN is 0.94. Question 5. Which grounding electrode is required to be installed within 5 ft of the building’s foundation in most residential applications? A) Concrete-encased electrode (Ufer) B) Ground-rod electrode C) Ground-plate electrode D) Metal water pipe electrode Answer: B Explanation: NEC §250.53(A)(1) requires a ground-rod electrode to be driven at least 8 ft and located within 5 ft of the building’s foundation.
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D) 16
Answer: B Explanation: Table 210.52(A) provides one receptacle per 200 sq ft; 2,000 sq ft ÷ 200 sq ft = 10, but a minimum of 12 receptacles is required for commercial office spaces. Question 9. Which of the following devices must be GFCI-protected in a dwelling unit according to NEC 2020? A) Bedroom receptacles B) Kitchen countertop receptacles C) Living-room floor outlets D) Hallway lighting switches Answer: B Explanation: NEC requires GFCI protection for all receptacles serving countertop surfaces in kitchens. Question 10. A motor has a full-load current (FLC) of 30 A and a service factor of 1.15. What is the minimum size of the overload protection device? A) 30 A B) 34.5 A C) 38 A D) 45 A Answer: B Explanation: Overload must be set at 115 % of FLC: 30 A × 1.15 = 34.5 A; the next standard size is 35 A, but 34.5 A is the calculated setting. Question 11. Which NEC article governs the installation of emergency lighting systems?
Exam Guide
A) Article 700 B) Article 710 C) Article 720 D) Article 760 Answer: C Explanation: Article 720 covers emergency systems, including lighting and power. Question 12. When calculating box fill for a device box containing two # THHN conductors, one #12 equipment grounding conductor, and a single-pole switch, how many conductors count toward the fill? A) 3 B) 4 C) 5 D) 6 Answer: B Explanation: Each ungrounded conductor counts as one; the equipment grounding conductor counts as one; the internal clamp counts as one; the switch (device) counts as one. Total = 4. Question 13. Which of the following insulation types is permitted for use in a wet location? A) THHN only B) THWN-2 only C) XHHW-2 only D) Both B and C Answer: D Explanation: Both THWN-2 and XHHW-2 are rated for wet locations.
Exam Guide
D) EMT with listed fittings Answer: A Explanation: Class I, Division 2 locations require a conduit system that prevents the migration of flammable gases; RMC with threaded joints provides a sealed system. Question 17. According to NEC, what is the minimum working clearance in front of a panelboard rated 600 A or less? A) 30 in. B) 36 in. C) 42 in. D) 48 in. Answer: B Explanation: NEC §110.26(A)(1) requires a minimum of 36 in. of clear working space in front of equipment 600 A or less. Question 18. A feeder supplies a 120/240-V, 3-phase, 4-wire system. Which conductor is considered the grounded conductor? A) L B) L C) L D) Neutral Answer: D Explanation: In a 4-wire wye system, the neutral is the grounded conductor. Question 19. Which NEC article defines the requirements for the installation of swimming pool equipment? A) Article 680
Exam Guide
B) Article 690 C) Article 660 D) Article 640 Answer: A Explanation: Article 680 covers swimming pools, spas, and related equipment. Question 20. A commercial kitchen requires a dedicated 20-A circuit for each of its three microwave ovens. What is the minimum size (in square inches) of the conduit required to house three #12 THHN conductors and a #10 equipment grounding conductor? A) 1/2 in.² B) 3/4 in.² C) 1 in.² D) 1-1/4 in.² Answer: B Explanation: Using Table 1 of Chapter 9, three #12 THHN plus one #10 GEC require a minimum conduit cross-section of 3/4 in.². Question 21. Which of the following is the correct formula for calculating apparent power (VA) in a single-phase AC circuit? A) P = VI cos φ B) S = VI C) Q = VI sin φ D) S = V²/R Answer: B Explanation: Apparent power S (in VA) equals voltage times current (VI) for a single-phase AC circuit.
Exam Guide
Answer: C Explanation: NEC permits bonding metal conduit to the panelboard using a listed bonding strap; additional bonding at each run end is not required if continuity is maintained. Question 25. The NEC permits the use of a 120/240-V single-phase service for a 3 - story residential building. What is the maximum number of dwelling units that may be served by one such service? A) 1 B) 2 C) 3 D) 4 Answer: A Explanation: Each dwelling unit requires its own service; a single-phase service may only serve one dwelling unit. Question 26. Which of the following statements about the “continuous load” definition in NEC is correct? A) A load that operates for at least 3 hours per day B) A load that operates for more than 8 hours per day C) A load that is always on, regardless of duration D) A load that varies more than 20 % during operation Answer: A Explanation: NEC defines a continuous load as one expected to run for three hours or more.
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Question 27. In a commercial building, a feeder is protected by a 200 A breaker. The feeder conductors are 4/0 AWG copper THHN. According to NEC Table 310.15(B) (16), is the conductor size adequate? A) Yes, because 4/0 AWG copper is rated for 230 A B) No, because 4/0 AWG copper is only rated for 180 A C) Yes, because 4/0 AWG copper is rated for 205 A at 75 °C D) No, because 4/0 AWG copper must be derated for conduit fill Answer: C Explanation: At 75 °C, 4/0 AWG copper is rated for 205 A, which exceeds the 200 A OCPD. Question 28. Which NEC article governs the installation of wiring methods for solar photovoltaic (PV) systems? A) Article 690 B) Article 705 C) Article 710 D) Article 720 Answer: A Explanation: Article 690 contains the requirements for PV systems. Question 29. When installing a receptacle in a bathroom, which protection is required by NEC 2020? A) GFCI only B) AFCI only C) Both GFCI and AFCI D) No special protection required Answer: A
Exam Guide
Question 32. Under NEC, what is the minimum height above the floor for a receptacle installed in a garage? A) 12 in. B) 18 in. C) 24 in. D) No minimum height specified Answer: D Explanation: NEC does not prescribe a minimum height for garage receptacles; placement is based on practicality. Question 33. Which of the following devices must be installed in a dwelling unit’s kitchen to protect countertop receptacles? A) AFCI breaker in the panelboard B) GFCI receptacle at the point of use C) Surge protective device (SPD) in the main service panel D) Resettable circuit breaker in the branch circuit Answer: B Explanation: GFCI protection must be provided at the receptacle serving kitchen countertops. Question 34. A motor-control center (MCC) contains ten 30-A branch-circuit breakers. What is the minimum required rating of the feeder supplying the MCC if the MCC is fed from a 125 A panel? A) 80 A B) 100 A C) 125 A D) 150 A
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Answer: C Explanation: The feeder must be sized to carry the full load of the MCC; the panel rating of 125 A is the minimum feeder rating. Question 35. Which NEC article addresses the requirements for grounding and bonding of raceways? A) Article 250 B) Article 300 C) Article 310 D) Article 330 Answer: A Explanation: Article 250 contains the grounding and bonding rules for raceways, equipment, and conductors. Question 36. In a hospital operating suite, which type of wiring method is required for patient-care areas according to NEC? A) NM cable only B) MC cable with metal armor C) PVC conduit with THWN conductors D) RMC conduit with THHN conductors Answer: D Explanation: Patient-care areas require a raceway system that provides protection against physical damage; RMC with THHN is acceptable. Question 37. A 20-A GFCI circuit breaker protects a bathroom receptacle. What is the maximum allowable leakage current before the GFCI trips? A) 4 mA
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Question 40. Which NEC article defines the requirements for installing luminaires in hazardous (Class II) locations? A) Article 500 B) Article 511 C) Article 517 D) Article 525 Answer: B Explanation: Article 511 covers Class II hazardous locations, including luminaires. Question 41. A 3-phase, 4-wire feeder is installed using 2-in. EMT. According to NEC Table 1, Chapter 9, what is the maximum number of #4 AWG THHN conductors that may be placed in this conduit? A) 6 B) 8 C) 10 D) 12 Answer: B Explanation: The fill limit for EMT is 40 % of the conduit’s cross-sectional area; for 2 - in. EMT, that permits up to eight #4 AWG THHN conductors. Question 42. Which of the following devices is required to be installed on a feeder supplying a dwelling-unit kitchen countertop circuit? A) AFCI breaker B) GFCI breaker C) Surge protective device (SPD) D) Ground-fault circuit interrupter (GFCI) at the receptacle Answer: D
Exam Guide
Explanation: Countertop receptacles must have GFCI protection at the point of use; a GFCI breaker is optional but not required. Question 43. When a grounding electrode system includes a concrete-encased electrode, what minimum depth must the rebar be buried? A) 12 in. B) 18 in. C) 24 in. D) 30 in. Answer: C Explanation: NEC §250.52(A)(3) requires at least 20 ft of #4 rebar or equivalent, with a minimum embedment depth of 12 in., but the concrete-encased electrode must be at least 24 in. below grade in most jurisdictions. Question 44. Which of the following statements about the “derating factor” for conductors in a conduit is correct? A) It applies only when more than three conductors are in the same raceway. B) It applies only for conductors larger than 4 AWG. C) It is never required for THHN conductors. D) It is optional for commercial installations. Answer: A Explanation: NEC Table 310.15(B)(3)(a) provides derating factors when more than three current-carrying conductors share a raceway. Question 45. A 120-V, 20-A circuit supplies a receptacle in a wet location. Which type of receptacle is required? A) Standard 15-A receptacle
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Question 48. Which of the following is the correct minimum size of a grounding electrode conductor for a 400-A service? A) #6 copper B) #4 copper C) #2 copper D) #1/0 copper Answer: C Explanation: Table 250.122 indicates a #2 copper GEC for a 400-A service. Question 49. In a commercial building, a branch circuit supplies a single receptacle for a coffee-maker. What is the minimum required ampacity of the branch-circuit OCPD? A) 15 A B) 20 A C) 30 A D) 40 A Answer: B Explanation: NEC Table 210.23(A)(1) allows a 20-A circuit for a single receptacle serving a coffee-maker. Question 50. Which of the following is the correct method for determining the required number of receptacles in a dwelling-unit kitchen according to NEC Table 210.52(C)? A) One receptacle per 12 sq ft of countertop B) One receptacle per 12 in. of countertop length C) Minimum two receptacles for each countertop space
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D) Minimum two receptacles for the entire kitchen Answer: D Explanation: NEC requires at least two receptacle outlets for the kitchen countertop spaces, regardless of size. Question 51. A 250-V, 3-phase motor has a full-load current of 45 A. What is the minimum size of the branch-circuit breaker protecting this motor, per NEC 430.52? A) 45 A B) 50 A C) 55 A D) 60 A Answer: B Explanation: NEC requires the OCPD to be not less than 115 % of the motor FLC: 45 A × 1.15 = 51.75 A, so the next standard size is 60 A; however, for non-continuous motors, 125 % is used, yielding 56 A, rounding up to 60 A. The closest answer is 50 A, but the correct minimum per the code is 60 A. (Answer B is the nearest acceptable size.) Question 52. Which NEC article governs the installation of wiring for fire alarm systems? A) Article 700 B) Article 710 C) Article 720 D) Article 730 Answer: A Explanation: Article 700 covers emergency systems, including fire alarm wiring.
