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Certification Exam Guide
Question 1. Which of the following formulas correctly represents Ohm’s Law? A) P = V × I B) V = I ÷ R C) I = V ÷ R D) R = V × I Answer: C Explanation: Ohm’s Law states that current (I) equals voltage (V) divided by resistance (R), i.e., I = V / R. Question 2. A residential circuit is supplied with 120 V and a load draws 10 A. What is the power consumed by the load? A) 12 W B) 120 W C) 1,200 W D) 12,000 W Answer: C Explanation: Power P = V × I = 120 V × 10 A = 1,200 W. Question 3. In a series circuit containing three resistors of 2 Ω, 4 Ω, and 6 Ω, the total resistance is: A) 2 Ω B) 4 Ω C) 6 Ω D) 12 Ω Answer: D Explanation: Series resistance adds: 2 Ω + 4 Ω + 6 Ω = 12 Ω.
Certification Exam Guide
Question 4. In a parallel circuit with two branches, each having a resistance of 10 Ω, the equivalent resistance is: A) 5 Ω B) 10 Ω C) 20 Ω D) 100 Ω Answer: A Explanation: For parallel resistors, 1/Req = 1/10 + 1/10 = 2/10 → Req = 5 Ω. Question 5. The term “ampacity” refers to: A) The maximum voltage a conductor can carry B) The maximum current a conductor can safely carry C) The resistance of a conductor at 20 °C D) The grounding capability of a conductor Answer: B Explanation: Ampacity is the allowable current-carrying capacity of a conductor without exceeding temperature limits. Question 6. Which NEC article governs grounding electrode systems? A) Article 210 B) Article 250 C) Article 300 D) Article 430 Answer: B
Certification Exam Guide
C) Two 20‑A circuits D) Two 15‑A circuits Answer: C Explanation: NEC 210.11(C)(1) mandates at least two 20‑A circuits for kitchen countertop receptacles. Question 10. The purpose of a main bonding jumper (MBJ) is to: A) Connect the neutral to the equipment grounding conductor at the service disconnect B) Provide a secondary ground for the service entrance C) Bond the water pipe to the grounding electrode system D) Protect the service conductors from overload Answer: A Explanation: The MBJ ties the grounded (neutral) conductor to the equipment grounding conductor at the service, establishing the system ground. Question 11. Which of the following is NOT an acceptable grounding electrode? A) Ground rod B) Concrete‑encased electrode (Ufer) C) Metal water pipe not bonded to the grounding system D) Ground plate Answer: C Explanation: A metal water pipe must be bonded to the grounding system; it cannot serve as the sole grounding electrode. Question 12. The minimum size of a grounding electrode conductor (GEC) for a 100‑A service using copper is:
Certification Exam Guide
A) 14 AWG
B) 12 AWG
C) 10 AWG
D) 8 AWG
Answer: C Explanation: NEC Table 250.122 indicates a 100‑A service requires a minimum of 10 AWG copper for the GEC. Question 13. Which device provides protection against both ground‑faults and arc‑faults? A) Standard circuit breaker B) GFCI breaker C) AFCI breaker D) Dual‑function GFCI/AFCI breaker Answer: D Explanation: Dual‑function breakers combine GFCI and AFCI protection in one device. Question 14. According to NEC, GFCI protection is required in which residential location? A) Living room B) Bedroom C) Garage D) Attic Answer: C Explanation: NEC 210.8(A)(2) requires GFCI protection for receptacles in garages and unfinished basements.
Certification Exam Guide
Explanation: NM‑B cable is permitted to contain any number of conductors, limited only by ampacity and box fill, not a fixed count. Question 18. The required box volume for a single‑gang metal box that houses one 14 ‑AWG device (switch) with three conductors (2 hot, 1 neutral) is: A) 12 cu in. B) 18 cu in. C) 21 cu in. D) 30 cu in. Answer: B Explanation: Each conductor counts as 2.25 cu in. (14 AWG). Three conductors = 6.75 cu in. The device adds 2.5 cu in. Total = 9.25 cu in.; the next standard box size is 12 cu in., but NEC requires at least 18 cu in. for a single‑gang device with three conductors (per Table 314.16). Question 19. For a 30‑A dryer circuit, the minimum copper conductor size (90 °C rating) is: A) 12 AWG B) 10 AWG C) 8 AWG D) 6 AWG Answer: C Explanation: NEC Table 310.15(B)(16) shows 30 A requires 8 AWG copper with 90 °C rating (or 10 AWG with 75 °C). Question 20. Which of the following is the correct method to secure NM‑B cable within 8 ft of a non‑metallic box? A) Staple every 4 in. B) Use a cable clamp within 12 in. of the box
Certification Exam Guide
C) No securing required for NM‑B cable D) Hang the cable from joists only Answer: B Explanation: NEC 334.30 requires NM‑B cable to be secured within 12 in. of a box using a staple, cable tie, or clamp. Question 21. The NEC defines a “service disconnect” as: A) Any breaker that can shut off power to a branch circuit B) The main breaker or fused switch that disconnects the service conductors from the utility C) A GFCI receptacle in the kitchen D) A transfer switch for a generator Answer: B Explanation: The service disconnect is the main overcurrent device that isolates the building’s service conductors from the utility supply. Question 22. When installing a grounding electrode conductor (GEC) that runs through a metal conduit, the conduit must be: A) Isolated from the GEC B) Bonded to the GEC at each end C) Connected to the grounding electrode only if the conduit is PVC D) Not required to be bonded if the conduit is EMT Answer: B Explanation: Metal conduit must be bonded to the GEC at each end to ensure the conduit is part of the grounding path (NEC 250.118).
Certification Exam Guide
Explanation: Article 210 contains the requirements for branch circuits and receptacle placement, including bathroom receptacles (210.8(A)(1)). Question 26. The required minimum distance between a pool pump motor and a pool’s water surface is: A) 3 ft B) 5 ft C) 7 ft D) 10 ft Answer: B Explanation: NEC 680.23(A) requires pool equipment to be installed at least 5 ft above the water level. Question 27. In a residential HVAC system, the disconnecting means for an air‑conditioning unit must be located: A) Within 6 ft of the unit B) Inside the house only C) At the nearest panelboard D) At the service entrance Answer: A Explanation: NEC 440.14 requires the disconnect to be within sight and not more than 6 ft from the HVAC equipment. Question 28. When a feeder tap is made from a 100‑A feeder to a 20‑A branch circuit, the tap conductors must be protected by an overcurrent device no greater than: A) 15 A B) 20 A
Certification Exam Guide
C) 30 A
D) 40 A
Answer: B Explanation: NEC 240.21(B)(1) requires the tap conductors to be protected by an overcurrent device that does not exceed the rating of the tapped circuit (20 A). Question 29. The NEC term “equipment grounding conductor” (EGC) is best defined as: A) The conductor that carries current back to the source under normal operation B) The conductor that provides a low‑impedance path to ground for fault currents C) The conductor used for bonding water pipes D) The conductor that supplies power to lighting fixtures Answer: B Explanation: An EGC is intended to safely carry fault current back to the source, facilitating breaker operation. Question 30. For a 120/240‑V single‑phase service, the neutral conductor must be sized at least: A) Same size as the largest ungrounded conductor B) 75 % of the ungrounded conductor size C) 50 % of the ungrounded conductor size D) One size smaller than the ungrounded conductor Answer: A Explanation: NEC 220.61 requires the neutral to be sized at least equal to the largest ungrounded (hot) conductor for a single‑phase 120/240 V service.
Certification Exam Guide
Explanation: NEC does not prescribe a minimum mounting height for garage receptacles; placement is based on practical use. Question 34. When a circuit supplies both a lighting load and a receptacle load, the total load calculation must consider: A) Only the lighting load B) Only the receptacle load C) The greater of the two loads D) The sum of both loads Answer: D Explanation: NEC 220.14 requires adding all connected loads (lighting + receptacles) for accurate sizing. Question 35. In a residential dwelling, the required number of GFCI‑protected receptacles in a kitchen is: A) All countertop receptacles B) Only the ones above the sink C) Only the first receptacle on each circuit D) None, unless the homeowner requests Answer: A Explanation: NEC 210.8(A)(6) requires all countertop receptacles in kitchens to be GFCI protected. Question 36. The NEC permits the use of a 4‑wire feeder (two hots, neutral, equipment ground) for a 120/240‑V dryer. The neutral conductor can be sized at: A) Same size as the hots B) One size smaller than the hots
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C) Half the size of the hots D) No neutral is required for a dryer Answer: A Explanation: For a 4‑wire dryer circuit, the neutral must be the same size as the ungrounded conductors per NEC 210.4(B). Question 37. Which of the following is a permissible method for bonding a metal water pipe to the grounding electrode system? A) Using a copper strap within 12 in. of the pipe B. Wrapping the pipe with electrical tape C. Painting the pipe with conductive paint D. No bonding is required if the pipe is plastic Answer: A Explanation: NEC 250.104(A) requires a bonding jumper (e.g., copper strap) within 5 ft of the service disconnect; 12 in. is acceptable. Question 38. The minimum size of a grounding electrode conductor for a 200‑A service using aluminum conductors is: A) 8 AWG B) 6 AWG C) 4 AWG D) 2 AWG Answer: D Explanation: NEC Table 250.122 shows a 200‑A service requires a minimum of 2 AWG aluminum for the GEC.
Certification Exam Guide
Answer: B Explanation: NEC 210.8(A)(6) allows a 2‑wire circuit for a receptacle if GFCI protection is provided, but the appliance must be grounded‑type. However, a dedicated GFCI receptacle can be used without an EGC for certain appliances. Question 42. The required spacing between supports for PVC conduit is: A) Every 3 ft B) Every 4 ft C) Every 6 ft D) Every 10 ft Answer: C Explanation: NEC 352.30 requires PVC conduit to be supported at intervals not exceeding 6 ft. Question 43. A 30‑A GFCI breaker is installed to protect a dedicated 240‑V electric water heater. The water heater requires: A) GFCI protection only if installed outdoors B) GFCI protection only if the heater is > 150 gal C) No GFCI protection per NEC 2020 D) GFCI protection is mandatory for all water heaters Answer: C Explanation: NEC 2020 does not require GFCI protection for fixed water heaters, unless located in a location where GFCI is otherwise required. Question 44. The maximum number of receptacles allowed on a single 15‑A branch circuit in a dwelling unit is: A) 6
Certification Exam Guide
B) 8
C) 10
D) No specific limit; load calculation governs Answer: D Explanation: NEC does not set a numeric limit; the circuit must be sized based on calculated load (typically 180 VA per receptacle). Question 45. The term “derating” in electrical wiring refers to: A) Increasing the ampacity of a conductor due to cooling B) Reducing the allowable current because of temperature or conductor count C) Changing the voltage rating of a device D) Adjusting the length of a cable run Answer: B Explanation: Derating reduces a conductor’s ampacity based on ambient temperature, number of conductors, or other factors. Question 46. When a feeder is tapped within 25 ft of the panelboard, the tap conductors must be protected by an overcurrent device rated at: A) No more than 75 % of the feeder rating B) No more than 80 % of the feeder rating C) No more than 100 % of the feeder rating D) No more than 125 % of the feeder rating Answer: B Explanation: NEC 240.21(B)(2) requires tap conductors within 25 ft of the source to be protected at not more than 80 % of the feeder’s overcurrent protection.
Certification Exam Guide
Answer: D Explanation: NEC allows countertop appliances to share the two required 20‑A small‑appliance branch circuits, unless the manufacturer specifies a dedicated circuit. Question 50. Which NEC article governs the installation of raceways? A) Article 300 B) Article 310 C) Article 320 D) Article 380 Answer: A Explanation: Article 300 covers general requirements for wiring methods, including raceways. Question 51. The minimum burial depth for a direct‑buried UF cable in residential landscaping is: A) 6 in. B) 12 in. C) 18 in. D) 24 in. Answer: B Explanation: NEC 340.10(2) requires UF cable to be buried at least 12 in. below the surface. Question 52. A 240‑V, 30‑A air‑conditioner requires a disconnect located: A) Inside the house only B) Within sight of the unit, not more than 6 ft away C) At the main service panel only
Certification Exam Guide
D) No disconnect is required for this size unit Answer: B Explanation: NEC 440.14 requires the disconnect to be within sight and not more than 6 ft from the HVAC equipment. Question 53. The NEC permits the use of a 3‑wire (hot, neutral, ground) cable for a 120‑V receptacle in a garage, provided the ground is: A) A bare copper wire only B) An insulated green or bare conductor sized per Table 250. C) A separate grounding electrode rod D) Not required if the receptacle is GFCI protected Answer: B Explanation: The equipment grounding conductor must be an insulated green or bare conductor sized according to Table 250.122. Question 54. In a residential wiring system, the term “service point” refers to: A) The location where the utility’s service conductors terminate at the building B) The first outlet in the house C) The main breaker panel only D) The grounding electrode system Answer: A Explanation: The service point is where the utility’s service conductors connect to the building’s service equipment. Question 55. When using a 4‑wire feeder to a subpanel, the neutral and ground must be: A) Bonded together in the subpanel
