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Question 1. Which NEC article defines the term “ampacity”? A) Article 100 B) Article 110 C) Article 210 D) Article 310 Answer: A Explanation: Article 100 contains definitions of terms used throughout the NEC, including “ampacity,” the maximum current a conductor can carry continuously under specified conditions. Question 2. Ohm’s Law is used to calculate which of the following relationships? A) Power = Voltage × Current B) Voltage = Current × Resistance C) Resistance = Power ÷ Current D) Current = Power ÷ Voltage Answer: B Explanation: Ohm’s Law states V = I × R, linking voltage, current, and resistance. Question 3. In a purely resistive AC circuit, the power factor is: A) 0 B) 0. C) 1 D) Depends on frequency Answer: C
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Explanation: For resistive loads, voltage and current are in phase, giving a power factor of unity (1). Question 4. Which conductor color is required for an insulated grounded (neutral) conductor in residential wiring? A) Black B) Red C) White or gray D) Green Answer: C Explanation: NEC requires neutrals to be identified by white or gray insulation. Question 5. The NEC permits the use of a shared neutral on a 3-wire, 120/240 V branch circuit when the loads are: A) Both continuous B) Non-continuous and on different phases C) Same-phase only D) Motor loads only Answer: B Explanation: A shared neutral is allowed when the two 120 V circuits are on opposite phases, balancing the neutral current. Question 6. The minimum working clearance in front of a service disconnecting means is: A) 3 ft
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Explanation: Table 310.15(B)(16) lists 4/0 AWG copper THHN at 100 A for 30 °C; no derating needed. Question 9. The required spacing between receptacles on a wall in a dwelling unit is: A) Every 4 ft B) Every 6 ft C) Every 8 ft D) Every 12 ft Answer: B Explanation: NEC 210.52(A)(1) mandates receptacles be placed so no point on a wall is more than 6 ft from an outlet. Question 10. The maximum number of service disconnects allowed in a single enclosure is: A) 2 B) 4 C) 6 D) No limit if listed Answer: A Explanation: NEC 230.71 limits the number of service disconnecting means in one enclosure to two. Question 11. The grounding electrode conductor (GEC) size for a 200-A service using copper is:
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A) 4 AWG
B) 2 AWG
C) 6 AWG
D) 8 AWG
Answer: B Explanation: Table 250.66 shows 2 AWG copper for a 200-A service. Question 12. An equipment grounding conductor (EGC) for a 20-A circuit protected by a 20-A breaker must be at least: A) 14 AWG copper B) 12 AWG copper C) 10 AWG copper D) 8 AWG copper Answer: A Explanation: Table 250.122 lists 14 AWG copper as the minimum size for a 20-A overcurrent device. Question 13. Which of the following is the correct method to identify a re-identifiable white conductor? A) Stripping the insulation B) Marking with black tape at its ends C) Using a permanent marker on the insulation D) Wrapping the conductor with green tape Answer: B
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A) 20 A
B) 30 A
C) 40 A
D) 50 A
Answer: B Explanation: Receptacles must be protected by an overcurrent device not exceeding the receptacle’s rating; thus a 30-A breaker. Question 17. Which type of conduit is permitted for installation in wet locations without a moisture-tight fitting? A) EMT B) Rigid Metal Conduit (RMC) C) Flexible Metal Conduit (FMC) D) PVC Schedule 40 Answer: B Explanation: RMC is listed for wet locations; EMT and FMC require moisture-tight fittings, PVC is plastic but also listed for wet locations. Question 18. The NEC requires a dedicated 20-A circuit for which of the following in a dwelling? A) Kitchen countertop receptacles B) Bathroom vanity lights C) Bedroom ceiling fans D) Living-room floor outlets
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Answer: A Explanation: NEC 210.52(C)(1) mandates a minimum of two 20-A circuits for kitchen countertop receptacles. Question 19. A motor-starting device that provides a reduced voltage during start is known as: A) Soft starter B) VFD C) Autotransformer starter D) Direct-on-line starter Answer: C Explanation: An autotransformer starter reduces voltage during start; a soft starter is electronic, VFD varies frequency, and DOL applies full voltage. Question 20. The minimum size of a copper grounding electrode conductor for a 100 - A service is: A) 6 AWG B) 8 AWG C) 10 AWG D) 12 AWG Answer: C Explanation: Table 250.66 lists 10 AWG copper for a 100-A service. Question 21. When calculating box fill, a device requiring a yoke counts as:
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Explanation: Plastic conduit is non-conductive and cannot serve as a grounding electrode. Question 24. In a three-phase, four-wire 120/208 V system, the neutral conductor carries current equal to: A) The sum of all phase currents B) Zero, always C) The vector sum of the three phase currents D) The highest phase current Answer: C Explanation: In a balanced three-phase system the neutral carries the vector sum, which is zero; in an unbalanced system it carries the vector sum of the phase currents. Question 25. For a 15-A, 120-V receptacle, the maximum length of a flexible cord used as a power supply is: A) 25 ft B) 50 ft C) 75 ft D) No limit if listed Answer: D Explanation: NEC does not limit the length of a listed flexible cord; it limits ampacity based on cord type. Question 26. Which of the following is a requirement for a GFCI receptacle installed in a residential bathroom?
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A) Must be on a dedicated 20-A circuit B) Must be a two-pole device C) Must be a dead-front type only D) Must be protected by an AFCI Answer: A Explanation: NEC 210.8(A)(1) requires bathroom receptacles to be GFCI-protected and supplied by a 20-A branch circuit. Question 27. A 240-V dryer circuit is protected by a 30-A breaker. The minimum copper conductor size (THHN) required is: A) 10 AWG B) 12 AWG C) 8 AWG D) 6 AWG Answer: A Explanation: Table 310.15(B)(16) shows 10 AWG copper THHN rated at 30 A. Question 28. The NEC permits the use of a “metallic raceway” as an equipment grounding conductor when: A) The raceway is continuous and bonded at each end B) The raceway is larger than 1-in schedule 40 PVC C) The raceway contains only one conductor D) The raceway is installed underground only Answer: A
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C) A dryer cycle lasting 30 min D) A microwave oven Answer: B Explanation: Continuous loads are those expected to run for three hours or more without interruption; a 24-hour lighting circuit qualifies. Question 32. The minimum size of a copper conductor for a 150-A service entrance is: A) 2/0 AWG B) 4/0 AWG C) 3/0 AWG D) 1/0 AWG Answer: C Explanation: Table 310.15(B)(16) lists 3/0 AWG copper as rated for 150 A. Question 33. In a residential garage, receptacles must be protected by a GFCI if they are: A) Within 6 ft of a sink B) Installed on a dedicated 20-A circuit C) Located at any height D) Rated 125 V, 15- or 20-A Answer: D Explanation: NEC 210.8(A)(2) requires GFCI protection for 125-V, 15- and 20-A receptacles in garages.
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Question 34. A Class I hazardous location requires which of the following for wiring methods? A) Non-conductive conduit only B) Explosion-proof (Ex d) equipment C) Metallic raceway with sealed fittings D) No special requirements if wiring is short Answer: B Explanation: Class I locations (gases, vapors) require explosion-proof (Ex d) equipment to prevent ignition. Question 35. The required minimum spacing between a swimming pool’s main bonding jumper and the nearest metallic pipe is: A) 6 in B) 12 in C) 18 in D) No spacing required Answer: B Explanation: NEC 680.26(A) requires the main bonding jumper to be within 12 in of any metallic pipe that is part of the pool’s grounding system. Question 36. An EV charging station rated at 40 A must be supplied from a branch circuit of at least: A) 30 A B) 40 A
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Question 39. The voltage drop limit recommended for feeder circuits in commercial installations is: A) 1 % B) 2 % C) 3 % D) 5 % Answer: B Explanation: NEC 210.19(A)(1) recommends a maximum of 2 % voltage drop for feeders to maintain efficient operation. Question 40. For a 120/240 V single-phase service, the neutral conductor is required to be: A) Larger than the hot conductors B) Same size as the hot conductors C) Smaller than the hot conductors D) Not required if a balanced load is present Answer: B Explanation: NEC 230.42 requires the neutral to be the same size as the ungrounded conductors for single-phase services. Question 41. Which of the following is the correct method to calculate the load for a commercial kitchen’s cooking equipment? A) Sum of name-plate ratings, no demand factor B) Apply a 75 % demand factor to the total name-plate rating C) Apply a 100 % demand factor to the first 10 kW, then 50 % thereafter
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D) Use a flat 30 % demand factor for all equipment Answer: C Explanation: NEC 220.55 requires 100 % of the first 10 kW of cooking equipment, then 50 % of the remainder. Question 42. The minimum clearance between a panelboard and the nearest combustible material is: A) 1 ft B) 3 ft C) 6 in D) 12 in Answer: D Explanation: NEC 110.26(A)(1) mandates a minimum of 6 in of working clearance, but for combustible material a 12 in clearance is required. Question 43. In a residential dwelling, the minimum number of receptacles required in a hallway that is 20 ft long is: A) One B) Two C) Three D) Four Answer: B Explanation: Receptacles must be placed so that no point is more than 6 ft from an outlet; a 20-ft hallway requires at least two receptacles.
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D) 100 % of the transformer’s full-load current Answer: B Explanation: NEC 450.3(B) requires primary overcurrent protection not to exceed 150 % of the transformer’s full-load current. Question 47. For a 240-V, 30-A dryer circuit using 10-AWG copper conductors, the required conduit fill for three conductors (two hots and a neutral) in ½-in EMT is: A) 40 % B) 53 % C) 68 % D) 80 % Answer: B Explanation: Table 1 in Chapter 9 shows that three 10-AWG conductors in ½-in EMT fill 53 % of the conduit’s cross-section, which is within the 53 % limit for three conductors. Question 48. Which of the following statements about AFCI protection is correct? A) All 15-A and 20-A circuits in a residence must have AFCI protection. B) AFCI protection is only required for kitchen countertop circuits. C) AFCI devices can be installed in place of GFCI devices. D) AFCI protection is optional for bedroom circuits. Answer: A Explanation: NEC 210.12(A) requires AFCI protection for all 120-V, 15- and 20-A branch circuits supplying outlets in dwelling unit living areas, bedrooms, and other areas.
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Question 49. The minimum height for a receptacle installed in a bathroom vanity area is: A) 12 in above the countertop B) 18 in above the countertop C) 24 in above the countertop D) No minimum height specified Answer: A Explanation: NEC 210.52(C)(1) requires bathroom receptacles to be installed at least 12 in above the countertop. Question 50. The NEC allows a “ground-fault circuit interrupter” (GFCI) to be installed in a panelboard to protect: A) Only the downstream receptacles B) The entire panelboard and all downstream circuits C) Only the branch circuit on which it is installed D) None of the above; GFCI cannot be installed in a panelboard Answer: C Explanation: A GFCI breaker protects the branch circuit it is installed on; it does not protect the entire panelboard. Question 51. For a three-wire, 120/240 V dryer circuit, the neutral conductor is required to be: A) 12 AWG copper B) 10 AWG copper
