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Question 1. Which NEC article specifically governs grounding and bonding of electrical systems? A) Article 210 B) Article 250 C) Article 310 D) Article 430 Answer: B Explanation: Article 250 of the NEC contains the requirements for grounding and bonding of electrical systems, including equipment grounding conductors and grounding electrodes. Question 2. In a three-phase, four-wire wye system, what is the voltage between any two line conductors if the line-to-neutral voltage is 120 V? A) 120 V B) 208 V C) 240 V D) 277 V Answer: B Explanation: Line-to-line voltage = √ 3 × line-to-neutral voltage = 1.732 × 120 V ≈ 208 V. Question 3. According to Ohm’s Law, what current will flow through a 10 Ω resistor connected to a 120 V source? A) 12 A B) 1.2 A C) 0.12 A D) 120 A
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Answer: B Explanation: I = V / R = 120 V / 10 Ω = 12 A. Question 4. Which of the following is the correct formula for calculating real power (P) in a single-phase AC circuit? A) P = V × I × cos θ B) P = V × I × sin θ C) P = V² / R D) P = I² × R Answer: A Explanation: Real power equals voltage times current times the power factor (cos θ). Question 5. A 1500 W motor operates at 240 V. What is its full-load current (FLC) assuming a power factor of 0.9 and efficiency of 85 %? A) 7.3 A B) 8.9 A C) 9.5 A D) 10.4 A Answer: B Explanation: P = V × I × PF × η → I = P / (V × PF × η) = 1500 W / (240 V × 0.9 × 0.85) ≈ 8.9 A. Question 6. Which type of conduit is permitted for outdoor wet locations in Maryland? A) Rigid Metal Conduit (RMC) only B) Electrical Metallic Tubing (EMT) only C) PVC Schedule 40 conduit
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A) A dedicated 240 V dryer circuit B) A 120 V receptacle for a workstation C) A 120 V receptacle for a refrigerator D) All of the above Answer: B Explanation: All 120 V, 15- or 20-A receptacles in garages must be GFCI-protected. Dedicated 240 V appliances are not required unless they serve a specific purpose. Question 10. The ampacity of a 3-conductor, 4-wire NM-B cable with #4 AWG aluminum conductors in a 75 °C column is: A) 55 A B) 65 A C) 70 A D) 85 A Answer: D Explanation: Table 310.15(B)(16) shows #4 AWG Al at 75 °C is rated for 85 A. Question 11. When calculating voltage drop, which factor is NOT included in the standard formula? A) Length of the conductor B) Conductor resistance per foot C) Power factor of the load D) Color of the insulation Answer: D Explanation: Insulation color has no effect on voltage drop calculations.
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Question 12. A transformer secondary is rated 240 V, 30 kVA. What is the full-load secondary current? A) 100 A B) 125 A C) 150 A D) 200 A Answer: B Explanation: I = kVA × 1000 / V = 30,000 VA / 240 V = 125 A. Question 13. Which NEC article governs the installation of electric vehicle charging equipment? A) Article 210 B) Article 625 C) Article 640 D) Article 690 Answer: B Explanation: Article 625 covers electric vehicle charging systems, including wiring methods and overcurrent protection. Question 14. In a commercial building, a fire alarm control panel requires a dedicated feeder. What is the minimum conductor size for a 20 A feeder using copper conductors in a 90 °C column? A) #12 AWG B) #10 AWG C) #8 AWG D) #6 AWG Answer: C
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A) 9
B) 12
C) 15
D) 20
Answer: C Explanation: Table 1 of Chapter 9 provides a maximum of 15 #12 AWG THHN conductors in 1-in. EMT. Question 18. In a hazardous (Class I, Division 2) location, which type of wiring method is permitted for power circuits? A) NM-B cable B) MC cable with PVC jacket C) Rigid Metal Conduit (RMC) only D) Flexible Metal Conduit (FMC) with flammable insulation Answer: C Explanation: Only raceways such as RMC, IMC, or steel conduit are permitted in Class I, Division 2 areas; NM-B and MC are not allowed. Question 19. What is the minimum clearance required between the top of a panelboard and the floor in a commercial installation? A) 30 in. B) 36 in. C) 42 in. D) No specific clearance, only working space is required. Answer: D Explanation: NEC 110.26 requires working space, not a fixed height clearance. The required clearances are based on the width and depth of the equipment, not a set distance from the floor.
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Question 20. A 150 A feeder supplies a 3-phase, 4-wire load. What is the minimum size of the grounding electrode conductor (GEC) required? A) #8 AWG copper B) #6 AWG copper C) #4 AWG copper D) #2 AWG copper Answer: B Explanation: Table 250.122 indicates a #6 AWG copper GEC for a 100- 150 A feeder. Question 21. Which device must be installed at the service disconnect for a dwelling with a total calculated load of 200 A? A) A fused disconnect B) A main breaker rated at 200 A C) A main breaker rated at 225 A D) No device is required if the service entrance conductors are protected elsewhere. Answer: B Explanation: The service disconnect must be rated at least equal to the calculated load; a 200 A main breaker meets this requirement. Question 22. In a three-wire, single-phase 120/240 V circuit, what is the purpose of the neutral conductor? A) To provide a return path for 240 V loads B) To serve as a grounding conductor C) To carry unbalanced current from the two 120 V legs D) To reduce voltage drop on the hot conductors
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C) 150 % of the motor’s name-plate FLC D) 200 % of the motor’s name-plate FLC Answer: B Explanation: NEC 430.22 requires conductors to be sized at least 125 % of the motor’s full-load current. Question 26. Which NEC article addresses the installation of swimming pool equipment? A) Article 680 B Question 27. A 3-phase, 4-wire feeder is protected by a 100 A breaker. What is the minimum size copper feeder conductor allowed by NEC Table 310.15(B)(16) at 75 °C? A) #4 AWG B) #3 AWG C) #2 AWG D) #1 AWG Answer: A Explanation: #4 AWG Cu at 75 °C is rated for 85 A; however, for a 100 A breaker the next larger size #3 AWG (100 A) is required. The correct answer is #3 AWG. (Corrected) Answer: B Explanation: Table 310.15(B)(16) shows #3 AWG copper at 75 °C rated for 100 A, which matches the breaker size. Question 28. Which of the following is the correct maximum height for a receptacle installed in a kitchen countertop area?
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A) 30 in. above the countertop B) 48 in. above the countertop C) 60 in. above the countertop D) No height limit, only spacing requirements apply Answer: B Explanation: NEC 210.52(C)(1) requires at least one receptacle outlet to be installed no higher than 48 in. above the countertop. Question 29. In a commercial office building, a lighting circuit is supplied by a 20 A breaker. The total calculated load is 14 A. What is the permissible demand factor for the lighting load? A) 100 % B) 80 % C) 70 % D) 65 % Answer: B Explanation: For general lighting loads, NEC Table 220.42 allows a demand factor of 80 % for the first 3 kW and 100 % thereafter; for a single 20 A circuit the 80 % rule applies. Question 30. Which type of raceway is permitted for use in a wet, underground location? A) EMT B) Rigid Metal Conduit (RMC) C) Flexible Metal Conduit (FMC) D) Non-metallic conduit (PVC) only Answer: D
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C) A non-listed pull-out fuse holder D) Any device that can open the circuit Answer: B Explanation: NEC 430.102 requires the disconnecting means for a motor to be a listed fusible switch, circuit breaker, or non-fused switching device that is listed for the purpose. Question 34. For a 120 V, 15 A receptacle in a dwelling, what is the maximum length of a flexible cord that can be used without violating NEC voltage-drop limits (assume 3 % allowable)? A) 25 ft B) 50 ft C) 75 ft D) 100 ft Answer: B Explanation: Using the voltage-drop formula Vdrop = 2 × K × I × L / A, with K≈12 for 12 AWG Cu, I = 15 A, A = 2 mm² (≈ 12 AWG), solving for L gives approximately 50 ft for a 3 % drop. Question 35. Which NEC article governs the installation of fire alarm circuits? A) Article 210 B) Article 300 C) Article 760 D) Article 800 Answer: C Explanation: Article 760 deals with fire alarm systems, including wiring methods and power supplies.
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Question 36. A 3-phase motor rated 5 hp, 460 V, 4-pole, 60 Hz requires a disconnect. What is the minimum size of the disconnecting means? A) 20 A B) 30 A C) 40 A D) 50 A Answer: B Explanation: NEC 430.30 requires a disconnect rated at least 125 % of the motor’s full-load current. A 5 hp 460 V motor has an FLC ≈ 23 A; 125 % of 23 A ≈ 28.8 A, so a 30 A disconnect is the minimum. Question 37. Which of the following is the correct color code for a 120 V, 3 - wire circuit that includes a grounded (neutral) conductor? A) Black, white, green B) Red, black, white C) Black, red, green D) White, gray, green Answer: A Explanation: For a 120 V circuit, the hot is black, neutral is white, and equipment grounding conductor is green (or bare). Question 38. In a commercial kitchen, what is the required rating for a receptacle that supplies a 20 A countertop cooking appliance? A) 15 A, 125 V B) 20 A, 125 V C) 20 A, 250 V D) 30 A, 125 V Answer: B
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C) Relying on the metal conduit itself as the equipment grounding path D) Using a separate insulated ground wire run parallel to the conduit Answer: A Explanation: Grounding screws are not a recognized method for grounding conduit; the conduit must be electrically continuous or a dedicated grounding conductor must be installed. Question 42. A 250 V, 10 kW electric heater is installed in a commercial space. What size circuit breaker is required for this heater? A) 40 A B) 45 A C) 50 A D) 60 A Answer: C Explanation: Heater current = 10,000 W / 250 V = 40 A. NEC requires OCPD ≥125 % of continuous load → 40 A × 1.25 = 50 A. Therefore a 50 A breaker is required. Question 43. Which of the following devices must be installed in a dwelling’s kitchen to protect against arc-faults? A) AFCI circuit breaker for all 120 V branch circuits B) GFCI receptacle for each countertop outlet C) AFCI receptacle for each countertop outlet D) Both AFCI breaker and GFCI receptacle for each countertop outlet Answer: A Explanation: NEC 210.12(A) requires AFCI protection for all 120 V, single-phase, 15- and 20-A branch circuits supplying outlets in dwelling unit kitchens.
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Question 44. In a residential panel, how many spaces must be left clear on either side of a circuit breaker for maintenance? A) 1 space B) 2 spaces C) 3 spaces D) No clearance required Answer: B Explanation: NEC 408.4 requires a minimum of two spaces (one on each side) clear of other breakers to provide adequate working space. Question 45. Which of the following is the correct minimum size for a grounding electrode conductor connected to a 200 A service? A) #8 AWG copper B) #6 AWG copper C) #4 AWG copper D) #2 AWG copper Answer: C Explanation: Table 250.66 indicates a #4 AWG copper GEC is required for a 200 A service. Question 46. A 12 kW, 240 V solar photovoltaic (PV) array is to be interconnected. What is the minimum size of the PV circuit’s overcurrent protective device? A) 20 A B) 30 A C) 40 A D) 50 A Answer: B
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C) Size the feeder based on the largest single load only D) Use the 100 % demand factor per NEC Table 220. Answer: B Explanation: NEC requires a 125 % demand factor for continuous loads such as commercial kitchen equipment. Question 48. What is the maximum distance a flexible cord may run from a receptacle to a portable tool without violating NEC voltage-drop limits (assume 3 % allowable, 14 AWG copper, 120 V, 12 A load)? A) 25 ft B) 50 ft C) 75 ft D) 100 ft Answer: B Explanation: Using the voltage-drop formula, a 14 A load on 14 AWG copper (K≈12) yields a maximum length of about 50 ft for a 3 % drop. Question 49. Which NEC article governs the installation of emergency power systems? A) Article 700 B) Article 710 C) Article 725 D) Article 740 Answer: A Explanation: Article 700 covers emergency systems, including generators and transfer equipment.
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Question 50. A 30 A, 240 V circuit supplies a water heater. The heater has a name-plate rating of 5500 W. Is the circuit appropriately sized? A) Yes, because the heater draws 22.9 A, which is below 30 A B) No, because the heater requires a 25 A breaker C) Yes, because the heater’s current is 30 A after applying the 125 % factor D) No, because the heater must be on a 40 A circuit Answer: A Explanation: Current = 5500 W / 240 V = 22.9 A. A 30 A breaker provides adequate protection and meets the 125 % continuous load requirement (22.9 A × 1.25 ≈ 28.6 A < 30 A). Question 51. Which of the following is the correct minimum size for a copper grounding electrode conductor for a 400 A service? A) #6 AWG B) #4 AWG C) #2 AWG D) #1/0 AWG Answer: D Explanation: Table 250.66 requires a #1/0 AWG copper GEC for services 301 A- 400 A. Question 52. For a conduit system installed in a 2-hour fire-rated wall, which of the following is required? A) Use of EMT only B) Use of fire-rated conduit such as RMC or IMC C) No special requirements, standard conduit is acceptable D) Conduit must be filled with fire-resistive sealant Answer: B
