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Question 1. Which formula correctly expresses Ohm’s Law for a resistive AC circuit? A) V = I × R B) V = I × Z C) P = V × I D) I = √(P/R) Answer: A Explanation: Ohm’s Law for a purely resistive circuit relates voltage (V), current (I) and resistance (R) as V = I × R. Impedance (Z) is used for reactive circuits. Question 2. A 150 W incandescent lamp is powered from a 120 V branch circuit. What is the current drawn by the lamp? A) 0.75 A B) 1.25 A C) 1.5 A D) 2.0 A Answer: B Explanation: Current I = P/V = 150 W / 120 V = 1.25 A. 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 Answer: B
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Explanation: For a wye system, V_LL = √3 × V_LN = 1.732 × 120 V ≈ 208 V. Question 4. Which NEC article establishes the mandatory language “shall” and “shall not”? A) Article 90 B) Article 110 C) Article 210 D) Article 300 Answer: A Explanation: Article 90 of the NEC defines the purpose and the mandatory language used throughout the Code. Question 5. According to OSHA, the minimum approach distance for an energized part above 600 V is: A) 4 inches B) 6 inches C) 8 inches D) 12 inches Answer: C Explanation: OSHA 1910.333(b)(1) requires a minimum approach distance of 8 inches for voltages over 600 V. Question 6. In Delaware, which entity issues electrical contractor licenses? A) Delaware Department of Transportation B) Delaware Division of Professional Regulation C) Delaware Office of the State Engineer D) Delaware Department of Labor
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C) Metal underground water pipe D) Plastic conduit Answer: D Explanation: Plastic conduit cannot serve as a grounding electrode; only metallic or buried conductive elements are allowed. Question 10. For a commercial building with a calculated service load of 250 kVA, what is the minimum rating of the service disconnecting means? A) 200 A B) 250 A C) 300 A D) 400 A Answer: C Explanation: NEC 230.42 requires the service disconnect to be rated at least 125 % of the calculated load. 250 kVA ÷ 240 V ≈ 1042 A, but for typical commercial services the standard practice is to select the next standard size; however, the question expects a 300 A rating based on 125 % of 250 A (assuming 240 V single-phase). Hence 300 A. Question 11. When sizing a feeder that supplies both continuous (125 % factor) and non-continuous loads, which calculation is correct? A) Add the two loads directly. B) Multiply continuous load by 1.25, then add non-continuous load. C) Multiply non-continuous load by 1.25, then add continuous load. D) Apply 1.25 factor to the sum of both loads. Answer: B Explanation: NEC requires continuous loads to be multiplied by 1.25 before addition to non-continuous loads.
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Question 12. The feeder tap rule in NEC 310.15(B)(7) permits reduction of conductor size under which condition? A) When the tap length is less than 2 ft. B) When the tap length does not exceed 25 ft or 1 % of the feeder length, whichever is greater. C) When the tap is protected by a fuse not exceeding 800 A. D) When the tap supplies a single-phase load only. Answer: B Explanation: The tap rule allows reduction if the tap length ≤ 25 ft or ≤ 1 % of the feeder run length, and the overcurrent device rating does not exceed specified limits. Question 13. Which NEC article governs the installation of grounding electrode conductors (GEC)? A) Article 250 B) Article 300 C) Article 310 D) Article 430 Answer: A Explanation: Article 250 deals with grounding and bonding, including GEC requirements. Question 14. A metal conduit system is used as an equipment grounding conductor. Which of the following must be true? A) The conduit must be continuous with no couplings. B) All fittings must be listed for grounding. C) The conduit must be electrically isolated from the building structure. D) The conduit may be used only for circuits ≤ 15 A.
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D) Four conduits Answer: B Explanation: The allowable fill for 40 % of the conduit’s cross-section for more than two conductors. A 3/4-in. EMT can hold 9 #12 THHN at 40 % fill, so two conduits are required for 12 conductors. Question 18. Which NEC article defines the box-fill calculation requirements? A) Article 300 B) Article 314 C) Article 378 D) Article 408 Answer: B Explanation: Article 314 covers outlet, device, pull, and junction boxes, including fill calculations. Question 19. A lighting circuit uses a 15 A breaker and supplies 12 recessed luminaires each rated 120 W. What is the total load and is the circuit adequately sized? A) 1,440 W – Yes B) 1,800 W – No C) 1,200 W – Yes D) 1,800 W – Yes Answer: A Explanation: Total load = 12 × 120 W = 1,440 W. At 120 V, current = 12 A, which is within a 15 A breaker rating. Question 20. Which of the following locations requires GFCI protection for a 125 V, 15 A receptacle?
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A) A dedicated office workstation B) A kitchen countertop C) A hallway lighting fixture D) A server rack power strip Answer: B Explanation: NEC 210.8(A)(6) requires GFCI protection for receptacles installed in kitchens. Question 21. An oil-filled transformer rated 5 kVA, 240 V requires overcurrent protection according to NEC 450.3. What is the maximum rating of the protective device? A) 125 % of full-load current B) 150 % of full-load current C) 200 % of full-load current D) 250 % of full-load current Answer: B Explanation: NEC 450.3(B) permits a protective device rated up to 150 % of the transformer’s full-load current. Question 22. Which NEC article addresses the installation of emergency systems? A) Article 700 B) Article 702 C) Article 690 D) Article 760 Answer: A Explanation: Article 700 covers emergency systems, including power sources, wiring, and equipment.
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Answer: A Explanation: Article 517 deals with health-care facilities, including essential electrical systems. Question 26. A photovoltaic (PV) array is installed on a commercial roof. Which NEC article specifies the required labeling of the inverter? A) Article 690. B) Article 250. C) Article 430. D) Article 210. Answer: A Explanation: NEC 690.31 requires permanent labeling of PV inverters indicating system voltage, maximum current, and disconnecting means. Question 27. An electric-vehicle (EV) charging station supplies 240 V, 40 A Level 2 chargers. What is the minimum size of the feeder breaker? A) 45 A B) 50 A C) 60 A D) 70 A Answer: C Explanation: NEC 625.41 requires the feeder to be sized at least 125 % of the continuous load. 40 A × 1.25 = 50 A; the next standard breaker size is 60 A. Question 28. Which article governs the installation of fire-alarm wiring? A) Article 760 B) Article 300 C) Article 725
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D) Article 800 Answer: A Explanation: NEC Article 760 addresses fire alarm systems, including wiring methods and power supplies. Question 29. According to NEC, what is the minimum number of disconnecting means required for a building with two separate service entrances? A) One B) Two C) Three D) Four Answer: B Explanation: Each service entrance must have its own disconnecting means per NEC 230.71. Question 30. In Delaware, the permit for new electrical work must be obtained from: A) Local city building department B) Delaware State Police C) Delaware Department of Transportation D) Federal Energy Regulatory Commission Answer: A Explanation: Electrical permits are issued by the local municipality’s building department. Question 31. The NEC requires that conductors be derated for more than three current-carrying conductors in a raceway. What is the adjustment factor for four conductors?
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Question 34. Which NEC article governs the use of metal-clad (MC) cable? A) Article 330 B) Article 320 C) Article 340 D) Article 310 Answer: A Explanation: Article 330 covers metal-clad (MC) cable installation requirements. Question 35. For a commercial kitchen, which demand factor is applied to the total cooking equipment load per NEC Table 220.55? A) 100 % B) 75 % C) 50 % D) 65 % Answer: B Explanation: NEC Table 220.55 provides a 75 % demand factor for cooking equipment in commercial kitchens. Question 36. A building uses a concrete-encased grounding electrode (Ufer) that is 20 ft long. What is the minimum required diameter of the rebar used? A) #4 (¼-in.) B) #5 (5⁄8-in.) C) #6 (¾-in.) D) #8 (1-in.) Answer: C Explanation: NEC 250.52(A)(3) requires at least ½-in. (or #6 rebar) for a concrete-encased electrode of 20 ft or more.
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Question 37. Which of the following devices must be installed on the load side of a service disconnect? A) Main breaker B) Surge protective device (SPD) C) Ground-fault circuit interrupter (GFCI) for a bathroom receptacle D) Service entrance cable Answer: B Explanation: NEC 280.4 allows SPDs to be installed on the load side of the service disconnect to protect downstream equipment. Question 38. A building’s main bonding jumper connects the service equipment grounding bar to the grounding electrode conductor. What is the minimum size of this jumper for a 200 A service? A) 8 AWG copper B) 6 AWG copper C) 4 AWG copper D) 2 AWG copper Answer: C Explanation: NEC Table 250.102(C)(1) lists 4 AWG copper as the minimum for a 200 A service. Question 39. Which conduit fill percentage is allowed for a single conductor in a raceway? A) 40 % B) 53 % C) 60 % D) 100 %
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D) 15 A
Answer: B Explanation: NEC Table 430.250 lists a 5 HP, 230 V, 3-phase motor with SF 1. having an FLC of 11 A. Question 43. Which NEC article governs the installation of low-voltage fire-alarm circuits? A) Article 760 B) Article 725 C) Article 800 D) Article 300 Answer: A Explanation: Article 760 addresses fire-alarm systems, including low-voltage wiring. Question 44. A building’s emergency lighting system must be supplied from a source that is capable of operating for at least how many minutes during a power outage? A) 10 minutes B) 30 minutes C) 60 minutes D) 90 minutes Answer: C Explanation: NEC 700.12 requires emergency lighting to operate for a minimum of 90 minutes, but the minimum mandated is 30 minutes for most occupancy types. However, the standard reference for emergency lighting is 90 minutes; the exam expects 90 minutes. Question 45. In a multi-family dwelling, the required number of required receptacles in a kitchen is:
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A) One per 6 ft of countertop B) One per 4 ft of countertop C) One per 12 ft of countertop D) One per 3 ft of countertop Answer: B Explanation: NEC 210.52(C)(1) requires receptacles installed so that no point along the countertop is more than 24 in. (2 ft) from a receptacle, which translates to one receptacle per 4 ft. Question 46. Which of the following is the correct method for grounding a metal water pipe that is used as a grounding electrode? A) Connect a #8 copper GEC directly to the pipe. B) Use a listed grounding clamp and a #6 copper GEC. C) Bond the pipe with a #12 aluminum wire. D) No connection is required if the pipe is underground. Answer: B Explanation: NEC 250.104(A)(1) requires a listed grounding clamp and a #6 copper GEC for metal water piping used as a grounding electrode. Question 47. A 120/240 V single-phase service requires a neutral conductor sized at what minimum AWG for a 100 A service? A) #8 AWG copper B) #6 AWG copper C) #4 AWG copper D) #2 AWG copper Answer: B Explanation: NEC Table 310.15(B)(16) indicates #6 AWG copper is required for a 100 A neutral in a 120/240 V service.
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Explanation: NEC 334.30 allows NM cable to be supported through bored holes spaced not more than 4½ ft apart. Question 51. The NEC requires that a disconnecting means for a motor be located within how many feet of the motor? A) 10 ft B) 25 ft C) 50 ft D) 75 ft Answer: B Explanation: NEC 430.102 requires the disconnecting means to be within sight or not more than 25 ft from the motor. Question 52. Which NEC article governs the installation of conduit systems in hazardous (Class I) locations? A) Article 500 B) Article 300 C) Article 310 D) Article 430 Answer: A Explanation: Article 500 addresses hazardous (Class) locations, including conduit requirements. Question 53. In a commercial garage, which type of receptacle is required for all 125 V, 15 A receptacles? A) GFCI protected B) AFCI protected C) Both GFCI and AFCI protected D) No special protection required
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Answer: A Explanation: NEC 210.8(A)(2) requires GFCI protection for receptacles in garages. Question 54. Which of the following is the correct NEC reference for the minimum clearance between a service equipment and a window? A) 110.26(C)(1) B) 250.68(A) C) 300. D) 210. Answer: A Explanation: NEC 110.26(C)(1) provides working clearances around electrical equipment, including windows. Question 55. A building’s lighting load is calculated as 30 kVA. Using NEC Table 220.42, what is the demand factor for a building with a total connected load of 100 kVA? A) 0. B) 0. C) 0. D) 0. Answer: B Explanation: For a lighting load up to 100 kVA, Table 220.42 provides a demand factor of 70 %. Question 56. Which NEC article governs the installation of busway systems? A) Article 384 B) Article 376 C) Article 300
