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Guide [MDJE]
Question 1. Which of the following equations correctly represents Ohm’s Law? A) P = V × I B) V = I × R C) I = V / P D) R = V × I Answer: B Explanation: Ohm’s Law states that voltage (V) equals current (I) multiplied by resistance (R). Question 2. In a series circuit, how does the current behave across each component? A) It increases after each component. B) It remains the same through all components. C) It decreases proportionally to resistance. D) It alternates between high and low values. Answer: B Explanation: Series circuits have a single path for current, so the same current flows through every component. Question 3. What is the primary difference between alternating current (AC) and direct current (DC)? A) AC flows only in one direction, DC changes direction. B) AC voltage remains constant, DC voltage varies sinusoidally. C) AC voltage reverses polarity periodically, DC voltage maintains a constant polarity. D) AC is used only for lighting, DC only for motors. Answer: C Explanation: AC periodically reverses polarity while DC maintains a single polarity. Question 4. A 150‑W incandescent lamp is connected to a 120‑V circuit. What is the current drawn by the lamp?
Guide [MDJE]
A) 0.8 A
B) 1.25 A
C) 12 A
D) 18 A
Answer: B Explanation: I = P / V = 150 W / 120 V = 1.25 A. Question 5. Which unit conversion is correct for 250 mA to amperes? A) 0.025 A B) 0.25 A C) 2.5 A D) 25 A Answer: B Explanation: 1 A = 1000 mA, so 250 mA = 0.25 A. Question 6. In a parallel circuit, the total voltage across each branch is: A) The sum of individual branch voltages. B) Equal to the source voltage. C) Half of the source voltage. D) Determined by the highest resistance branch. Answer: B Explanation: All parallel branches share the same voltage equal to the source voltage. Question 7. Which NEC article defines the requirements for grounded (neutral) conductors? A) Article 200 B) Article 210 C) Article 250
Guide [MDJE]
Answer: B Explanation: Article 250 contains the requirements for grounding electrode systems, equipment grounding, and bonding. Question 11. Which of the following is considered a grounding electrode? A) A metal water pipe in direct contact with earth. B) The neutral bus bar inside a panel. C) An equipment grounding conductor. D) A branch‑circuit hot conductor. Answer: A Explanation: Metal water pipes that are in direct contact with the earth can serve as grounding electrodes. Question 12. When calculating the load for a dwelling’s kitchen, which NEC demand factor is applied to the first 3 kW of cooking equipment? A) 100 % B) 75 % C) 50 % D) 25 % Answer: A Explanation: The first 3 kW of cooking appliances are counted at 100 % for the dwelling load calculation. Question 13. What is the minimum conduit fill percentage for a single conductor in a raceway? A) 10 % B) 20 % C) 40 % D) 53 %
Guide [MDJE]
Answer: B Explanation: NEC Chapter 9, Table 1 requires a minimum of 20 % fill for a single conductor. Question 14. In a metal conduit system, which of the following is required to maintain continuity of the equipment grounding conductor? A) Use of a separate grounding wire. B) Bonding each conduit section with a grounding bushing. C) Installing a GFCI at the panel. D) Using only PVC conduit. Answer: B Explanation: Metal conduit must be electrically continuous; grounding bushings or fittings ensure the conduit remains bonded. Question 15. Which raceway type is permitted for outdoor installation without a moisture barrier? A) EMT (Electrical Metallic Tubing) B) PVC (Non‑metallic) conduit C) RMC (Rigid Metal Conduit) D) NM cable Answer: C Explanation: Rigid Metal Conduit (RMC) is listed for outdoor use and provides protection against moisture. Question 16. According to NEC Table 314.16(B), a single-gang device box (3 in³) can accommodate how many #12 AWG insulated conductors? A) 2 B) 3 C) 4 D) 5
Guide [MDJE]
C) Garages with a dedicated 240‑V circuit. D) Wet locations such as bathrooms. Answer: B Explanation: NEC 210.12(A) mandates AFCI protection for all 120‑V, 15‑ and 20‑A branch circuits supplying bedroom outlets. Question 20. Which NEC article governs the installation of luminaires (lighting fixtures)? A) Article 300 B) Article 410 C) Article 430 D) Article 440 Answer: B Explanation: Article 410 contains the requirements for luminaires, including mounting, spacing, and protection. Question 21. For a 240‑V, 30‑A electric dryer, what is the minimum size of copper branch‑circuit conductor? A) 12 AWG B) 10 AWG C) 8 AWG D) 6 AWG Answer: B Explanation: A 30‑A dryer circuit requires at least 10 AWG copper per Table 310.15(B)(16). Question 22. Which of the following is the correct method to disconnect a water heater that is hard‑wired? A) Install a pull‑out disconnect box within 6 ft of the heater. B) Use a fused disconnect outside the building.
Guide [MDJE]
C) No disconnect required if the heater is under 1500 W. D) Install a GFCI breaker at the panel. Answer: A Explanation: NEC 422.31 requires a readily accessible disconnect within 6 ft of the appliance for hard‑wired water heaters. Question 23. A single‑phase, 3‑hp motor operates at 230 V. What is the approximate full‑load current (FLC) using NEC Table 430.250? A) 5 A B) 8 A C) 12 A D) 16 A Answer: B Explanation: Table 430.250 shows a 3‑hp, 230‑V, 1‑phase motor has an FLC of about 8 A. Question 24. When selecting a conduit size for three #8 AWG THHN conductors, which conduit diameter is the minimum that meets the 40 % fill rule? A) ½‑in. EMT B) ¾‑in. EMT C) 1‑in. EMT D) 1¼‑in. EMT Answer: B Explanation: Three #8 THHN occupy 0.040 in² each; total 0.12 in². ½‑in. EMT has a 40 % fill area of 0.122 in², just meeting the limit, but NEC requires rounding up, so ¾‑in. EMT is the safe minimum. Question 25. Which of the following statements about NM (Romex) cable is true? A) It may be installed in wet locations. B) It is permitted in conduit for protection.
Guide [MDJE]
C) 50 ft D) 75 ft Answer: C Explanation: NEC 690.13 requires the DC disconnect to be within 50 ft of the PV array or as close as practicable. Question 29. Which of the following is a permissible method for grounding a metal conduit system serving a detached garage? A) Connecting the conduit to the building’s main grounding electrode. B) Installing a separate grounding electrode at the garage and bonding the conduit to it. C) Using a GFCI breaker in the main panel only. D) No grounding is required for detached structures. Answer: B Explanation: Detached structures must have their own grounding electrode system bonded to the metal conduit. Question 30. What is the minimum size of grounding electrode conductor (GEC) required for a 100 ‑A service? A) #12 AWG copper B) #10 AWG copper C) #8 AWG copper D) #6 AWG copper Answer: B Explanation: NEC Table 250.66 indicates a #10 AWG copper GEC for services up to 100 A. Question 31. In a three‑wire, 120/240‑V single‑phase system, which conductor is identified by white insulation? A) Ungrounded (hot) conductor B) Grounded (neutral) conductor
Guide [MDJE]
C) Equipment grounding conductor D) Reserved for a future circuit Answer: B Explanation: White (or gray) insulation identifies the neutral (grounded) conductor. Question 32. When installing a receptacle in a bathroom, which protection is required? A) AFCI only B) GFCI only C) Both AFCI and GFCI D) No special protection needed Answer: B Explanation: NEC 210.8(A)(1) mandates GFCI protection for all bathroom receptacles. Question 33. A 30‑A, 240‑V circuit supplies a residential air‑conditioning unit. What is the minimum size of copper feeder conductor? A) 12 AWG B) 10 AWG C) 8 AWG D) 6 AWG Answer: C Explanation: Per Table 310.15(B)(16), a 30‑A circuit requires at least 8 AWG copper. Question 34. Which of the following is NOT a permitted use for a 12‑AWG aluminum conductor? A) Branch‑circuit wiring in a dwelling. B) Service entrance conductors. C) Grounding electrode conductors.
Guide [MDJE]
D) Article 408 Answer: B Explanation: Article 392 covers the installation of cable trays. Question 38. For a 120‑V, 15‑A receptacle in a garage, which protection devices are required? A) GFCI only B) AFCI only C) Both GFCI and AFCI D) No special protection Answer: A Explanation: NEC 210.8(A)(2) requires GFCI protection for garage receptacles; AFCI is not required. Question 39. Which of the following best describes the purpose of a main bonding jumper (MBJ)? A) To connect the neutral to the grounding electrode system at the service. B) To provide a backup overcurrent device. C) To isolate the service neutral from the earth. D) To protect against short circuits in branch circuits. Answer: A Explanation: The MBJ bonds the service neutral to the grounding electrode system, establishing a reference to earth. Question 40. An electrician needs to install a 3‑wire, 120/240‑V service for a new residential home. What is the minimum size of the grounding electrode conductor (copper) for a 200‑A service? A) #8 AWG B) #6 AWG C) #4 AWG
Guide [MDJE]
D) #2 AWG
Answer: C Explanation: Table 250.66 specifies #4 AWG copper for services 151 A to 200 A. Question 41. Which of the following is a requirement for a listed GFCI receptacle installed in a wet location? A) It must be recessed at least 6 in. from the surface. B) It must have a weather‑proof cover rated for the location. C) It must be installed on a dedicated circuit. D) It must be connected to a separate neutral. Answer: B Explanation: GFCI receptacles in wet locations must be protected by an in‑use (weather‑proof) cover. Question 42. When sizing a feeder to a subpanel that will serve a 20‑A kitchen circuit, a 30‑A lighting circuit, and a 15‑A dryer circuit, what is the minimum feeder ampacity after applying demand factors? A) 40 A B) 50 A C) 60 A D) 70 A Answer: B Explanation: Apply NEC demand factors: 100 % of the first 3 kW of cooking (≈12.5 A), 100 % of dryer (15 A), 100 % of lighting (30 A). Total ≈57.5 A; using the next standard size, 60 A. However, after demand factor adjustments (e.g., 80 % for lighting), the calculated load reduces to about 50 A, making 50 A the minimum standard feeder size. Question 43. Which of the following is the correct method for installing a grounding electrode conductor to a concrete‑encased electrode (Ufer)? A) Clamp the GEC to the rebar before concrete is poured.
Guide [MDJE]
B) They detect series and parallel arcing conditions. C) They are required for all 240‑V circuits. D) They must be installed at every receptacle. Answer: B Explanation: AFCI breakers are designed to detect both series and parallel arc‑fault conditions. Question 47. The maximum number of conductors allowed in a ½‑in. EMT conduit for #12 THHN, assuming 40 % fill, is: A) 4 B) 5 C) 6 D) 7 Answer: C Explanation: ½‑in. EMT has a 40 % fill area of 0.122 in². Each #12 THHN is 0.0133 in². 0.122 ÷ 0. ≈ 9, but only 6 conductors are allowed per NEC Table 1 for a single conduit size. Therefore, 6 is the correct maximum. Question 48. Which NEC article governs the installation of electric signs? A) Article 300 B) Article 600 C) Article 610 D) Article 620 Answer: B Explanation: Article 600 covers the requirements for electric signs and outline lighting. Question 49. In a residential dwelling, what is the minimum height for a receptacle installed in a kitchen countertop area? A) 12 in. above the countertop
Guide [MDJE]
B) 15 in. above the countertop C) 18 in. above the countertop D) No minimum height required Answer: C Explanation: NEC 210.52(C)(1) requires countertop receptacles to be no more than 20 in. above the countertop surface; the common practice is 18 in. Question 50. When a feeder supplies more than three current‑carrying conductors, which NEC table provides the adjustment factors? A) Table 310.15(B)(2)(a) B) Table 310.15(B)(3)(a) C) Table 310. D) Table 310. Answer: B Explanation: Table 310.15(B)(3)(a) lists ampacity adjustment factors for more than three current‑carrying conductors. Question 51. A 20‑A GFCI breaker protects a branch circuit that feeds a bathroom vanity light and a receptacle. Which of the following is true? A) The GFCI protection is unnecessary for the light. B) The GFCI must be installed at the receptacle, not the breaker. C) The breaker provides required protection for both devices. D) An AFCI is also required for this circuit. Answer: C Explanation: A GFCI breaker protects all downstream devices on the circuit, satisfying the requirement for the receptacle and providing protection for the light. Question 52. Which of the following is the proper method to identify a 4‑wire feeder in a conduit when only the outer sheath color is visible?
Guide [MDJE]
A) AFCI only B) GFCI only C) Both AFCI and GFCI D) No special protection Answer: B Explanation: NEC 210.8(A)(10) requires GFCI protection for laundry room receptacles. Question 56. When installing a conduit in a concrete wall, what is the minimum cover depth for PVC conduit containing up to three 4‑AWG conductors? A) 6 in. B) 12 in. C) 18 in. D) 24 in. Answer: B Explanation: NEC Table 300.5 specifies a minimum cover of 12 in. for PVC conduit with up to three 4 ‑AWG conductors. Question 57. Which of the following devices must be installed on a branch circuit that supplies a garage door opener? A) GFCI receptacle only B) AFCI breaker only C) Both GFCI and AFCI D) No special device required Answer: A Explanation: NEC 210.8(A)(2) requires GFCI protection for garage receptacles, which includes garage door opener circuits. Question 58. For a 3‑phase, 4‑wire, 208‑V system, what color is typically used for the neutral conductor?
Guide [MDJE]
A) Black B) Red C) White D) Green Answer: C Explanation: White (or gray) is the standard color for neutral in both single‑ and three‑phase systems. Question 59. Which NEC article governs the installation of fire alarm circuits? A) Article 300 B) Article 760 C) Article 770 D) Article 800 Answer: B Explanation: Article 760 covers fire alarm systems, including wiring methods and protection. Question 60. A 240‑V, 30‑A dryer circuit uses 10‑AWG copper conductors. If the ambient temperature is 40 °C, what is the corrected ampacity? A) 30 A (no correction) B) 35 A C) 28 A D) 25 A Answer: C Explanation: At 40 °C, the 75 °C column requires a 90 % correction factor; 30 A × 0.9 = 27 A, rounded up to 28 A. Question 61. Which of the following is a permitted method for securing NM cable to a stud? A) Staples placed every 4 in.
