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Question 1. Which NEC article governs the installation of grounding electrode systems? A) Article 250 B) Article 310 C) Article 210 D) Article 430 Answer: A Explanation: Article 250 of the NEC specifies the requirements for grounding and bonding, including grounding electrode systems. Question 2. The minimum size copper grounding electrode conductor for a 100 - amp service is: A) #12 AWG B) #10 AWG C) #8 AWG D) #6 AWG Answer: B Explanation: Table 250.66 requires a #10 AWG copper conductor for a 100-A service. Question 3. In a three-wire, single-phase, 120/240-V system, the neutral must be: A) Connected to ground at every outlet B) Isolated from ground except at the service disconnect C) Run in a separate conduit from the hot conductors D) Sized the same as the ungrounded conductors Answer: B Explanation: The neutral is bonded to ground only at the service equipment to prevent multiple return paths. Question 4. Which type of conduit is permitted for use in wet locations? A) Rigid Metal Conduit (RMC) only
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B) Electrical Metallic Tubing (EMT) only C) PVC Schedule 40 conduit D) Flexible Metal Conduit (FMC) only Answer: C Explanation: PVC Schedule 40 is rated for wet locations; RMC and EMT are also allowed, but PVC is the most common answer. Question 5. The maximum number of 14-AWG THHN conductors allowed in a single ¾-in. EMT without derating is: A) 2 B) 3 C) 4 D) 5 Answer: C Explanation: Table 312.2 permits up to 4 conductors of 14 AWG in a ¾-in. EMT before applying fill limits. Question 6. A circuit breaker rated at 125 % of the continuous load is required for which type of load? A) Lighting only B) Motors running less than 3 hours continuously C) Any load that operates for 3 hours or more continuously D) Non-continuous loads only Answer: C Explanation: NEC 210.20(A) requires breakers to be sized at least 125 % of continuous loads (≥3 h). Question 7. The color code for a 120-V AC circuit's grounded (neutral) conductor is: A) Black B) Red C) White
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Question 11. The minimum height for a receptacle outlet in a dwelling kitchen countertop is: A) 12 in. above the countertop B) 15 in. above the countertop C) 18 in. above the countertop D) 24 in. above the countertop Answer: B Explanation: NEC 210.52(C)(1) requires countertop receptacles to be no more than 20 in. above the surface; 15 in. is typical. Question 12. For a three-phase, four-wire 120/208-V system, the phase voltage between any two hot conductors is: A) 120 V B) 208 V C) 240 V D) 277 V Answer: B Explanation: In a 120/208-V three-phase system, line-to-line voltage is 208 V. Question 13. The purpose of a GFCI is to protect against: A) Over-current B) Over-voltage C) Ground faults D) Short circuits Answer: C Explanation: Ground-Fault Circuit Interrupters detect imbalances between hot and neutral currents, protecting against ground faults. Question 14. Which of the following is NOT a permitted method for grounding a service-entrance conductor? A) Direct burial copper rod
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B) Concrete-encased electrode C) Metal water pipe not bonded within 5 ft of the service disconnect D) Aluminum structural steel frame Answer: D Explanation: Structural steel may be used only if it is part of the grounding electrode system and properly bonded; otherwise, it is not a permitted grounding electrode. Question 15. The maximum length of a flexible cord used as a permanent wiring method is: A) 25 ft B) 50 ft C) 75 ft D) No specific limit, but it must not be used as a permanent wiring method Answer: D Explanation: Flexible cords are not permitted for permanent wiring; they are for temporary or portable equipment. Question 16. The minimum conduit fill for a single insulated conductor in a raceway is: A) 25 % B) 31 % C) 40 % D) 53 % Answer: B Explanation: NEC Table 1, Chapter 9 requires a minimum of 31 % fill for a single conductor. Question 17. A 30-amp, 240-V dryer circuit must be protected by a breaker sized at: A) 25 A B) 30 A C) 35 A
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Explanation: Dangerous (hazardous) locations are those with flammable or explosive atmospheres. Question 21. The required ampacity of a feeder conductor that supplies a 40 - amp continuous load, with a demand factor of 0.8, is: A) 32 A B) 40 A C) 50 A D) 62 A Answer: C Explanation: Continuous load × 125 % = 40 A × 1.25 = 50 A. Demand factor is irrelevant for continuous loads. Question 22. Which of the following is the correct method to identify a 4-wire, 120/240-V residential service conductor in the field? A) Red, Black, White, Green B) Black, White, Blue, Yellow C) Red, Blue, Yellow, Green D) Black, Red, White, Green Answer: D Explanation: Typical identification uses two hot conductors (black, red), a neutral (white), and a ground (green). Question 23. The maximum distance a receptacle can be from the point of attachment on a branch circuit in a dwelling unit is: A) 30 ft B) 50 ft C) 75 ft D) 100 ft Answer: B Explanation: NEC 210.24 limits the length of a branch-circuit to 50 ft for receptacle outlets in dwelling units.
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Question 24. For a fire alarm system, the minimum conductor size for Class A wiring is: A) #14 AWG copper B) #12 AWG copper C) #10 AWG copper D) #8 AWG copper Answer: B Explanation: NEC 760.41 requires a minimum of #12 AWG copper for Class A fire alarm circuits. Question 25. Which of the following devices must be installed on all 125-V, single-phase, 15- and 20-amp receptacles in a bathroom? A) AFCI B) GFCI C) Surge protector D) Circuit breaker Answer: B Explanation: NEC 210.8(A)(1) mandates GFCI protection for bathroom receptacles. Question 26. The purpose of a “dead-front” on a panelboard is to: A) Prevent accidental contact with live parts B) Provide a mounting surface for breakers C) Allow for heat dissipation D) Indicate the panel’s rating Answer: A Explanation: A dead-front shields live bus bars and terminals from accidental touch. Question 27. In a three-wire, single-phase circuit, the neutral conductor must be sized at least:
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D) Is protected by a separate service disconnect Answer: B Explanation: Dedicated circuits are allocated for a specific appliance or equipment, such as a refrigerator or a water heater. Question 31. The temperature rating for THHN conductors is: A) 60 °C B) 75 °C C) 90 °C D) 105 °C Answer: C Explanation: THHN insulation is rated for 90 °C in dry locations. Question 32. Which of the following is the correct formula to calculate voltage drop for a single-phase circuit? A) Vd = 2 × K × I × L / CM B) Vd = K × I × L / CM² C) Vd = 2 × K × I × L / CM² D) Vd = K × I × L / CM Answer: A Explanation: Voltage drop (Vd) = 2 × K (resistivity constant) × current × length ÷ circular mil area (CM) for single-phase. Question 33. Which NEC article addresses the installation of emergency systems? A) Article 700 B) Article 210 C) Article 430 D) Article 620 Answer: A Explanation: Article 700 covers emergency systems, including power sources and wiring requirements.
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Question 34. A “multi-wire branch circuit” (MWBC) must have its ungrounded conductors: A) Same color B) Opposite phases C) Same phase D) No specific requirement Answer: B Explanation: MWBCs share a neutral and must have ungrounded conductors on opposite phases to balance the neutral current. Question 35. The NEC requires that conduit fill shall not exceed what percentage for more than two conductors? A) 25 % B) 31 % C) 40 % D) 53 % Answer: C Explanation: Table 1, Chapter 9 specifies a maximum of 40 % conduit fill when three or more conductors are present. Question 36. For a motor rated 5 hp, 230 V, 3-phase, the minimum size of the branch-circuit breaker is: A) 15 A B) 20 A C) 30 A D) 40 A Answer: C Explanation: NEC Table 430.52 lists a 30 A breaker for a 5-hp, 230 V, 3-phase motor.
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C) 25 ft of the point where the service conductors enter the building D) No distance limitation Answer: B Explanation: NEC 230.71 requires the service disconnect to be within 10 ft of the service entrance point. Question 41. Which of the following is the correct definition of “ampacity”? A) The maximum voltage a conductor can safely carry B) The maximum current a conductor can carry without exceeding its temperature rating C) The resistance of a conductor per foot D) The power factor of a load Answer: B Explanation: Ampacity is the current-carrying capacity of a conductor under specified conditions. Question 42. The NEC permits the use of aluminum conductors for service-entrance conductors provided they are: A) 100 % sized compared to copper B) 125 % sized compared to copper C) 150 % sized compared to copper D) No size adjustment required Answer: B Explanation: Aluminum conductors must be sized 125 % of the equivalent copper conductor for the same ampacity. Question 43. Which type of fire alarm system requires its wiring to be installed in a separate raceway from power wiring? A) Conventional system B) Addressable system C) Mass notification system D) None; they may share the same raceway if separated by a barrier
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Answer: D Explanation: NEC 760.41 allows fire alarm circuits to share a raceway with power conductors if the conductors are separated by a physical barrier or the raceway is listed for both. Question 44. The required size of a grounding electrode conductor for a 400 - amp service is: A) #6 AWG copper B) #4 AWG copper C) #2 AWG copper D) #1/0 AWG copper Answer: D Explanation: Table 250.66 indicates #1/0 AWG copper for a 400-A service. Question 45. For a 120-V, 20-amp receptacle circuit, the maximum number of receptacles allowed is: A) 8 B) 10 C) 12 D) No specific limit, as long as load calculations are satisfied Answer: D Explanation: NEC does not set a numeric limit; the number of receptacles is governed by load calculations and spacing requirements. Question 46. Which of the following is the correct method to identify a 4-wire, 277/480-V three-phase system? A) Black, Red, Blue, White B) Brown, Orange, Yellow, Green C) L1, L2, L3, N D) A, B, C, D Answer: C
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Question 50. The voltage rating for a standard NM-B (Romex) cable is: A) 300 V B) 600 V C) 900 V D) 1200 V Answer: B Explanation: NM-B cable is rated for 600 V. Question 51. Which type of conduit is specifically listed for use in fire-rated assemblies without additional fireproofing? A) Rigid Metal Conduit (RMC) B) EMT C) Flexible Metal Conduit (FMC) D) PVC Schedule 40 Answer: A Explanation: RMC is non-combustible and can be used in fire-rated assemblies as listed. Question 52. The NEC requires that all exposed live parts of a panelboard be: A) Painted black B) Marked with “Live” signs C) Covered with a dead-front D) Connected to a surge protector Answer: C Explanation: A dead-front prevents accidental contact with live bus bars. Question 53. For a 120/240-V, single-phase, 3-wire feeder supplying a detached garage, the neutral must be: A) Isolated from ground at the garage panel B) Bonded to ground at both the service and garage panel C) Only bonded at the service disconnect
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D) Not required at all Answer: C Explanation: The neutral is bonded to ground only at the first means of disconnect (the service). Question 54. The minimum size of a grounding electrode conductor for a 150 - amp service using a ground rod is: A) #8 AWG copper B) #6 AWG copper C) #4 AWG copper D) #2 AWG copper Answer: B Explanation: Table 250.66 indicates #6 AWG copper for a 150-A service. Question 55. A “lockout-tagout” (LOTO) procedure is primarily intended to protect workers from: A) Electrical shock only B) Mechanical hazards only C) Unexpected energization or startup of equipment D) Arc flash only Answer: C Explanation: LOTO ensures that equipment cannot be inadvertently energized or started while work is performed. Question 56. The required minimum clearance between a ladder and a live overhead conductor is: A) 4 ft B) 6 ft C) 8 ft D) 10 ft Answer: C
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Question 60. Which of the following is the correct labeling requirement for a circuit that supplies only a bathroom vanity light? A) “Bathroom Light” B) “Bathroom – Lighting” C) “Lighting – Bathroom” D) Any label is acceptable as long as it is legible Answer: B Explanation: NEC 210.4 requires a descriptive label indicating the area and purpose; “Bathroom – Lighting” satisfies this. Question 61. The minimum size of a feeder conductor supplying a 60-amp, 240 - V load, using copper with 75 °C insulation, is: A) #6 AWG B) #8 AWG C) #10 AWG D) #12 AWG Answer: B Explanation: #8 AWG copper at 75 °C is rated for 55 A; however, for a 60-A load, the next size up (#6 AWG) is required. Correct answer is #6 AWG. Correction: Answer: A Explanation: #6 AWG copper at 75 °C provides 65 A, satisfying the 60-A requirement. Question 62. A “dedicated grounding electrode conductor” must be installed when: A) The service equipment is located in a detached building B) The grounding electrode is a metal water pipe C) A separate grounding electrode is used for a generator D) The grounding electrode is a concrete-encased electrode Answer: C
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Explanation: Generators require a dedicated grounding electrode conductor separate from the building’s main grounding system. Question 63. Which of the following is the correct method to terminate a grounding electrode conductor to a concrete-encased electrode? A) Clamp to the rebar with a listed grounding clamp B) Wrap around the rebar and solder C) Use a twist-on connector D) No connection required if the electrode is within 6 ft of the service panel Answer: A Explanation: NEC 250.70(A)(2) requires a listed grounding clamp to connect to the rebar. Question 64. The NEC requires that any circuit supplying a kitchen countertop receptacle be protected by a GFCI. This protection can be provided by: A) A GFCI breaker in the panel only B) A GFCI receptacle only C) Either a GFCI breaker or a GFCI receptacle D) Neither; only AFCI is required Answer: C Explanation: NEC 210.8(A)(6) allows either a GFCI breaker or a GFCI receptacle for protection. Question 65. The allowable voltage drop for feeder circuits supplying lighting loads is limited to: A) 1 % B) 2 % C) 3 % D) 5 % Answer: C Explanation: NEC recommends a maximum of 3 % voltage drop for feeders and branch circuits combined.
