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Question 1. Which formula correctly expresses Ohm’s Law? Answer: A Explanation: Ohm’s Law is V = I × R, relating voltage, current, and resistance. Question 2. In a series circuit, the total resistance is: A) The sum of individual resistances B) The reciprocal of the sum of reciprocals C) Always equal to the smallest resistor D) Independent of the number of resistors Answer: A Explanation: Series resistances add directly: R_total = R1 + R2 + … Question 3. For a purely resistive AC load, the power factor is: A) 0 B) 0. C) 1 D) – 1 Answer: C Explanation: Resistive loads have voltage and current in phase, giving PF = 1. Question 4. The reactance of an inductor is proportional to: A) Frequency and inductance B) Frequency only C) Inductance only D) Inverse of frequency Answer: A Explanation: XL = 2πfL, so it increases with both frequency and inductance. Question 5. In a balanced three‑phase wye system, the line voltage is:
A) √3 times the phase voltage B) √3 divided by the phase voltage C) Equal to the phase voltage D) Twice the phase voltage Answer: A Explanation: V_L = √3 × V_Ph for a wye‑connected balanced system. Question 6. Kirchhoff’s Current Law (KCL) states that at any node: A) Sum of currents entering = sum leaving B) Sum of voltages around a loop = 0 C) Power is conserved D) Resistance is constant Answer: A Explanation: KCL is the principle of charge conservation at a junction. Question 7. When using a multimeter to measure resistance, the circuit must be: A) Powered on B) De‑energized and isolated C) Connected to ground D) In parallel with a load Answer: B Explanation: Measuring resistance on a live circuit can damage the meter and give false readings. Question 8. A continuity test on a multimeter will indicate a short if the resistance is: A) Greater than 1 MΩ B) Exactly 0 Ω C) Less than 10 Ω D) Infinite Answer: C
C) Is always on standby D) Is only used during emergencies Answer: A Explanation: Continuous loads run for ≥3 hours and require conductor sizing at 125 % of load. Question 13. The minimum working space width in front of a panelboard is: A) 24 in. B) 30 in. C) 36 in. D) 48 in. Answer: C Explanation: NEC 110.26 requires at least 36 in. of clear width. Question 14. The required headroom clearance above electrical equipment is: A) 6 ft B) 6 ft 6 in. C) 7 ft D) 8 ft Answer: B Explanation: NEC 110.26 requires a minimum of 6 ft 6 in. from the floor to the underside of equipment. Question 15. To calculate a residential service size, the NEC requires: A) 100 % of the calculated load B) 125 % of the calculated load C) 150 % of the calculated load D) 200 % of the calculated load Answer: B Explanation: Service conductors must be sized for 125 % of the calculated load.
Question 16. The largest allowable conduit fill for a single conductor in a raceway is: A) 20 % B) 30 % C) 40 % D) 53 % Answer: B Explanation: For a single conductor, the fill limit is 53 % of the conduit’s cross‑section; however, the NEC limits it to 30 % for a single insulated conductor to avoid overheating. Question 17. When multiple conductors are bundled, the ampacity correction factor at 75 °C is: A) 1. B) 0. C) 0. D) 0. Answer: B Explanation: For 4–6 conductors in a raceway, NEC Table 310.15(B)(3)(a) gives a 0.80 factor. Question 18. The color code for a grounded (neutral) conductor in a 120/240 V system is: A) Black B) Red C) White D) Green Answer: C Explanation: White (or gray) indicates a neutral conductor. Question 19. A 4‑wire feeder to a subpanel must have: A) Two hots, one neutral, no ground B) Two hots, one neutral, one equipment grounding conductor C) Three hots, one neutral
Question 23. THHN conductors are rated for use in: A) Only wet locations B) Only dry locations C) Both wet and dry locations, up to 90 °C D) Only in conduit Answer: C Explanation: THHN is rated 90 °C in dry and 75 °C in wet locations, and may be used in conduit. Question 24. The ampacity of a 12‑AWG copper conductor with 75 °C insulation in a raceway with three other conductors is: A) 20 A B) 25 A C) 30 A D) 35 A Answer: B Explanation: Base ampacity is 30 A; with 4 conductors the correction factor is 0.80, giving 24 A (rounded up to 25 A per NEC tables). Question 25. The maximum number of 90‑degree bends allowed between pull points in a conduit run is: A) 4 B) 6 C) 8 D) 10 Answer: B Explanation: NEC 358.30 permits up to 6 bends (equivalent to 360°) before a pull point is required. Question 26. The required box fill for a single‑gang device box containing one switch, one ground, and one hot conductor is:
A) 2 cu in. B) 4 cu in. C) 6 cu in. D) 8 cu in. Answer: B Explanation: Each conductor counts as 1 cu in.; the device counts as 2 cu in.; total = 1+1+2 = 4 cu in. Question 27. NM‑B cable must be installed: A) In conduit in all locations B) Only where it is protected from physical damage C) Only outdoors D) Only in metal raceways Answer: B Explanation: NM‑B (Romex) can be exposed where it’s protected from damage, such as in walls. Question 28. Armored Cable (AC) is permitted for: A) Wet locations only B) Exposed work in dry locations C) Direct burial D) All of the above Answer: B Explanation: AC is for dry, exposed locations; it is not rated for wet or direct‑buried use. Question 29. The short‑circuit current rating (SCCR) of a panelboard must be at least: A) 10 kA B) 20 kA C) 30 kA D) 42 kA Answer: C
A) 2 ft apart B) 3 ft apart C) 4 ft apart D) 6 ft apart Answer: C Explanation: NEC 210.52(C) requires receptacles not more than 4 ft apart measured along the countertop. Question 34. A single‑pole 15‑A breaker can protect a 14‑AWG copper branch circuit because: A) 14‑AWG is rated for 15 A at 60 °C B) 14‑AWG is rated for 20 A C) Breaker rating is irrelevant D) 14‑AWG is only for 30 A circuits Answer: A Explanation: 14‑AWG copper is rated 15 A at 60 °C, matching the breaker size. Question 35. The required disconnecting means for a 5 kW, 240‑V air‑conditioning unit must be: A) A fuse only B) A 30 A circuit breaker C) A 20 A circuit breaker D) A 15 A circuit breaker Answer: B Explanation: FLC ≈ 5 kW/240 V = 20.8 A; NEC requires the breaker not exceed 125 % of FLC, so a 30 A breaker is appropriate. Question 36. The primary overcurrent protection for a 10 kVA, 480‑V transformer must be rated at least: A) 15 A B) 20 A C) 25 A
D) 30 A
Answer: D Explanation: Primary full‑load current = (10 kVA)/(√ 3 × 480 V) ≈ 12 A; NEC requires protection not less than 125 % → 15 A, but standard sizes lead to a 20 A breaker; however the next standard size that meets 125 % is 20 A. (Answer adjusted to 20 A) Answer: B Explanation: 125 % of 12 A = 15 A; the next standard breaker is 20 A. Question 37. A standby generator supplying emergency power must be connected through: A) A direct‑wired circuit B) A transfer switch C) A standard circuit breaker only D) An outlet receptacle Answer: B Explanation: NEC 702.11 requires a listed transfer switch to isolate utility power. Question 38. The minimum size of conductors for a 30‑A single‑phase motor (FLC 28 A) using 75 °C THHN is: A) 10 AWG B) 8 AWG C) 6 AWG D) 4 AWG Answer: B Explanation: Table 310.16 gives 40 A for 8 AWG at 75 °C; this exceeds the motor’s 125 % requirement (35 A). Question 39. Motor overload protection must be set to protect the motor at: A) 80 % of FLC B) 100 % of FLC C) 115 % of FLC D) 150 % of FLC
A) 14 AWG
B) 12 AWG
C) 10 AWG
D) 8 AWG
Answer: B Explanation: 20‑A circuits require 12 AWG copper per NEC 240.4(D). Question 44. The required clearance from a service disconnect to the nearest combustible material is: A) 1 ft B) 2 ft C) 3 ft D) 4 ft Answer: B Explanation: NEC 110.12(A) requires a minimum of 2 ft clearance. Question 45. A conduit fill of 40 % is permitted for: A) One conductor only B) Two conductors only C) Three or more conductors D) No situation; maximum is 30 % Answer: C Explanation: NEC Table 1 allows 40 % fill for three or more conductors. Question 46. The NEC defines “accessible” as: A) Capable of being reached without removing barriers B) Capable of being reached only with a ladder C) Capable of being reached after removing a cover plate D) Capable of being reached only by a qualified person
Answer: A Explanation: “Accessible” means without using tools or removing parts of the building. Question 47. The minimum size of a grounding electrode conductor for a 200‑A service using copper is: A) 8 AWG B) 6 AWG C) 4 AWG D) 2 AWG Answer: C Explanation: Table 250.66 specifies 4 AWG copper for a 200‑A service. Question 48. For a 3‑phase, 4‑wire feeder supplying a subpanel, the neutral must be: A) Isolated from ground at the subpanel B) Bonded to ground at the subpanel C) Not present D) Connected to the equipment grounding conductor Answer: A Explanation: The neutral is isolated in the subpanel; grounding is provided by a separate EGC. Question 49. The NEC requires that a receptacle in a bathroom be GFCI protected and have a minimum rating of: A) 15 A, 125 V B) 20 A, 125 V C) 15 A, 250 V D) 20 A, 250 V Answer: A Explanation: NEC 210.8(A)(1) requires 15‑ or 20‑A, 125‑V receptacles with GFCI in bathrooms; 15 A is the minimum.
D) Only bonded if the conduit is underground Answer: B Explanation: NEC 250.118 requires bonding of metal raceways at each box using a bonding jumper or approved method. Question 54. A lighting circuit that supplies dimmable LED fixtures must use which type of breaker? A) Standard thermal magnetic only B) AFCI‑type only C) GFCI‑type only D) Either standard or AFCI, depending on location Answer: D Explanation: AFCI is required in dwelling living areas; otherwise a standard breaker is acceptable. Question 55. The minimum clearance between a panelboard and a combustible wall is: A) 1 ft B) 2 ft C) 3 ft D) 4 ft Answer: B Explanation: NEC 110.12(A) requires 2 ft clearance from the front of the panel to any combustible material. Question 56. The NEC permits the use of aluminum conductors for feeder circuits if they are: A) 90 °C rated and have the appropriate ampacity adjustment B) Only used in service entrance only C) Not allowed for any feeder use D) Only used in underground raceways Answer: A Explanation: Aluminum conductors must be rated for 90 °C and sized per Table 310.15(B)(16) with appropriate adjustments.
Question 57. The required rating for a GFCI breaker protecting a 20‑A kitchen countertop circuit is: A) 15 A B) 20 A C) 30 A D) 40 A Answer: B Explanation: The breaker must match the circuit’s overcurrent rating; a 20‑A GFCI breaker is used. Question 58. A conduit that is listed for underground use must be: A) Rigid metal conduit (RMC) only B) PVC or RMC with proper markings C) EMT only D) Any metal conduit Answer: B Explanation: PVC conduit and RMC are both listed for direct burial when marked accordingly. Question 59. The NEC requires that a receptacle in a laundry area be GFCI protected because: A) All receptacles in a dwelling require GFCI B) Laundry areas are considered wet locations C) Only 240‑V receptacles need GFCI D) None of the above Answer: B Explanation: NEC 210.8(A)(6) mandates GFCI for laundry receptacles due to the presence of water. Question 60. The minimum conductor size for a 120‑V, 30‑A circuit supplying a water heater is: A) 12 AWG B) 10 AWG C) 8 AWG
Question 64. The NEC requires that a receptacle in a commercial office space be installed at a height of: A) 12 in. above the floor B) 18 in. above the floor C) 30 in. above the floor D) No specific height, as long as it is accessible Answer: D Explanation: NEC does not prescribe a specific height for commercial receptacles; accessibility is the key. Question 65. For a 240‑V, 50‑A welder circuit, the required conduit size for three 6‑AWG THHN conductors is: A) 1/2‑in. EMT B) 3/4‑in. EMT C) 1‑in. EMT D) 1‑1/4‑in. EMT Answer: B Explanation: 6‑AWG THHN has an area of 0.0507 in²; three conductors total 0.152 in². 3/4‑in. EMT allows 40 % fill (0.213 in²), so it is sufficient. Question 66. The minimum rating for a disconnecting means for a single‑phase, 3‑wire, 120/240‑V, 60 ‑A service is: A) 50 A B) 60 A C) 70 A D) 80 A Answer: B Explanation: The disconnect must be rated equal to or greater than the service overcurrent device, i.e., 60 A.
Question 67. A circuit supplying a bathroom exhaust fan must have: A) GFCI protection only B) AFCI protection only C) Both GFCI and AFCI protection D) Neither, unless the fan is > 150 W Answer: A Explanation: NEC 210.8(A)(1) requires GFCI for bathroom receptacles; fans on a dedicated circuit are not required to have GFCI unless they are on a receptacle. Question 68. The NEC allows the use of a single‑pole breaker to protect a multi‑wire branch circuit (MWBC) only if: A) The breakers are not tied together B) The breakers are handle‑tied or a two‑pole breaker is used C) The circuit is under 15 A D) The neutral is larger than the hots Answer: B Explanation: MWBC hots must be disconnectable simultaneously; handle‑tied or two‑pole breakers provide this. Question 69. For a fire alarm system, the minimum conductor size for the power circuit 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 fire alarm power circuits. Question 70. The required spacing between outlets on a garage wall is: A) 6 ft B) 8 ft
