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Contractor Ultimate Exam
Question 1. Which NEC article defines the term “grounded conductor”? A) Article 100 B) Article 250 C) Article 310 D) Article 430 Answer: A Explanation: Article 100 contains definitions for terms used throughout the NEC, including “grounded conductor”. Question 2. Ohm’s Law states that current equals voltage divided by resistance. Which formula correctly represents this relationship? A) I = V × R B) I = V / R C) I = R / V D) I = V² / R Answer: B Explanation: Ohm’s Law is I = V / R, where I is current, V is voltage, and R is resistance. Question 3. In a single-phase, 120/240 V residential service, what is the voltage between the two hot conductors? A) 120 V B) 240 V C) 208 V D) 277 V Answer: B Explanation: The two hot legs are 180° out of phase, giving a line-to-line voltage of 240 V. Question 4. When reading a wiring diagram, the symbol of a circle with three lines inside represents which device?
Contractor Ultimate Exam
A) Switch B) Receptacle C) Lamp (luminaire) D) Junction box Answer: C Explanation: The NEC symbol for a luminaire is a circle with three lines (representing a light source). Question 5. Which permit is typically required before installing a new service entrance in Wyoming? A) Electrical permit only B) Building permit only C) Both electrical and building permits D) No permit is required if the work is under 100 A Answer: C Explanation: Wyoming requires both a building permit (for structural work) and an electrical permit for service-entrance installations. Question 6. The first mandatory field inspection for a new residential service is usually performed after which step? A) Completion of the service disconnect B) Installation of the grounding electrode system C) Rough-in of the service-entrance conductors D) Final connection of the utility meter Answer: C Explanation: The rough-in inspection verifies correct sizing and routing of service-entrance conductors before they are covered. Question 7. A single-family dwelling has a calculated service load of 115 A. What is the minimum size of the service disconnect? A) 100 A
Contractor Ultimate Exam
D) 1 1/2 in. Answer: B Explanation: NEC Table 300.5 requires a minimum 3/4-in. conduit for 4 AWG copper conductors used in a 100 A service. Question 11. The purpose of the main bonding jumper (MBJ) is to: A) Connect the neutral to the grounding electrode conductor at the service disconnect B) Bond all equipment grounding conductors together C) Provide a low-impedance path for fault current to the utility transformer D) Both A and C Answer: D Explanation: The MBJ connects neutral to the grounding electrode system and creates a low-impedance fault path. Question 12. Which grounding electrode is NOT permitted as the sole grounding electrode for a detached garage? A) Concrete-encased electrode (Ufer) B) Ground rod C) Metal water pipe D) Metal underground tank Answer: B Explanation: A single ground rod is insufficient; at least two grounding electrodes are required for a detached structure. Question 13. A transformer supplying a 208 V, 3-phase load is rated at 75 kVA. What is the full-load current on the secondary? A) 208 A B) 208 V / √ C) 75,000 VA / (208 V × √3) D) 75,000 VA / 208 V
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Answer: C Explanation: Full-load current I = kVA / (V_LL × √3). Calculation: 75,000 VA / (208 V × 1.732) ≈ 209 A. Question 14. Overcurrent protection for a transformer secondary must be selected based on which NEC rule? A) 240.6(A) standard ampere rating table only B) 450.3(A) for transformers C) 430.32 for motor loads only D) 310.15(B)(16) temperature correction only Answer: B Explanation: NEC 450.3(A) governs overcurrent protection for transformers, using the transformer rating and conductors. Question 15. Temporary construction power for a site with a maximum demand of 200 kW should be supplied from a generator with a minimum rating of: A) 150 kW B) 200 kW C) 250 kW D) 300 kW Answer: C Explanation: NEC 590.4 requires a 125 % safety factor for temporary power, so 200 kW × 1.25 = 250 kW. Question 16. When calculating service load for a multi-family building, which demand factor is applied to the first 10 kW of lighting? A) 100 % B) 70 % C) 50 % D) 30 % Answer: B
Contractor Ultimate Exam
Question 20. The NEC maximum voltage drop recommended for feeder circuits is: 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. Question 21. A 250-ft run of 120/240 V, 20 A circuit uses 12 AWG copper THHN. What is the approximate voltage drop? (Use 2 % per 100 ft for 12 AWG). A) 1 % B) 2 % C) 5 % D) 10 % Answer: C Explanation: 250 ft ≈ 2.5 × 100 ft → 2 % × 2.5 = 5 % voltage drop. Question 22. GFCI protection is required for all of the following EXCEPT: A) Bathroom receptacles B) Outdoor receptacles C) Kitchen countertop receptacles D) Unfinished basement lighting fixtures Answer: D Explanation: NEC 210.8 requires GFCI for receptacles in listed locations; lighting fixtures are not covered. Question 23. AFCI protection is mandatory for which type of circuit in a dwelling unit?
Contractor Ultimate Exam
A) 15-A or 20-A 120-V branch circuits supplying outlets in living rooms B) 30-A circuits feeding electric dryers C) 15-A circuits feeding outdoor lighting D) All 120-V circuits regardless of location Answer: A Explanation: NEC 210.12(A) requires AFCI on 15-A and 20-A circuits supplying outlets in dwelling unit living areas. Question 24. Which raceway type is permitted for direct burial without a conduit? A) EMT B) RMC C) PVC Schedule 40 D) UF cable in the trench Answer: D Explanation: UF (Underground Feeder) cable is rated for direct burial and does not require conduit. Question 25. The maximum fill for a conduit containing more than two conductors of the same size is: A) 40 % B) 31 % C) 53 % D) 60 % Answer: B Explanation: NEC Table 1, Chapter 9 limits conduit fill to 31 % for three or more conductors. Question 26. When using EMT, the minimum conduit wall thickness for a 1-in. trade size is: A) 0.035 in.
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C) NEMA 4
D) NEMA 6
Answer: C Explanation: Damped locations require NEMA 4 (or higher) enclosures for luminaires. Question 30. The required burial depth for a 20-A PVC conduit carrying residential feeder circuits under a driveway is: A) 12 in. B) 18 in. C) 24 in. D) 30 in. Answer: B Explanation: NEC 300.5(D) mandates a minimum of 18 in. burial for PVC conduit under a driveway. Question 31. A 20-A branch circuit supplying a kitchen countertop receptacle must be protected by which type of breaker? A) Standard thermal-magnetic B) GFCI-type C) AFCI-type only D) Dual-function AFCI/GFCI Answer: B Explanation: NEC 210.8(A)(6) requires GFCI protection for all kitchen countertop receptacles. Question 32. Which of the following is NOT a permissible method for grounding a metal conduit system? A) Using a grounding electrode conductor attached to the conduit B) Installing a grounding strap at each conduit bend C) Bonding the conduit to the equipment grounding conductor at each box D) Relying solely on the conduit’s continuity without additional bonding
Contractor Ultimate Exam
Answer: D Explanation: NEC requires a dedicated grounding conductor or bonding straps; conduit continuity alone is insufficient. Question 33. A 30-kW, 208-V three-phase motor requires a full-load current of approximately 83 A. What size copper conductors (THHN) should be used for the branch circuit, assuming 75 °C rating? A) 4 AWG B) 2 AWG C) 1/0 AWG D) 2/0 AWG Answer: B Explanation: Table 310.15(B)(16) shows 2 AWG copper THHN rated at 115 A (75 °C), which exceeds the 83 A requirement. Question 34. The NEC requires a short-circuit and ground-fault protective device (SCGFPD) for motor circuits of what rating or less? A) 30 A B) 50 A C) 100 A D) 250 A Answer: C Explanation: NEC 430.32 requires an SCGFPD for motor circuits rated 100 A or less. Question 35. When wiring a magnetic starter for a three-phase motor, the control circuit must be protected by a fuse or breaker of what rating relative to the motor’s full-load current? A) Not more than 150 % of full-load current B) Not more than 250 % of full-load current C) Not more than 100 % of full-load current D) Not more than 200 % of full-load current
Contractor Ultimate Exam
Question 39. Redundant grounding in a hospital operating suite is required to ensure: A) Lower voltage drop on lighting circuits B) Continuity of the grounding path during a fault on any equipment C) Faster operation of emergency generators D) Compatibility with non-metallic conduit systems Answer: B Explanation: Redundant grounding provides a continuous low-impedance path even if one grounding electrode fails, critical for patient safety. Question 40. The required bonding grid for a swimming pool must be installed at what maximum spacing? A) 4 ft B) 6 ft C) 8 ft D) 10 ft Answer: B Explanation: NEC 680.26(A) requires a bonding grid with conductors spaced no more than 6 ft apart. Question 41. A standby generator supplying a building’s essential loads must be sized to provide at least what percentage of the calculated load? A) 80 % B) 90 % C) 100 % D) 110 % Answer: C Explanation: NEC 702.3(A) requires the generator to be capable of meeting 100 % of the essential load.
Contractor Ultimate Exam
Question 42. Which type of transfer switch is required for a generator that supplies both the building’s essential loads and optional loads? A) Non-automatic transfer switch (NATS) only B) Automatic transfer switch (ATS) only C) Either NATS or ATS, as long as it is listed for the application D) No transfer switch is required if the generator is directly wired to a panel Answer: C Explanation: NEC permits either a listed NATS or ATS for generator connections, provided the switch is rated for the load. Question 43. The NEC requires a minimum of how many disconnecting means for a motor controller cabinet that houses three separate motor starters? A) One per motor starter B) One per motor controller cabinet only C) Two total, regardless of number of starters D) No disconnecting means if the cabinet is locked Answer: A Explanation: Each motor must have a dedicated disconnecting means per NEC 430.102. Question 44. When selecting a fuse for a motor overload relay, the fuse rating must be: A) Equal to the motor’s full-load current B) Between 125 % and 150 % of the motor’s full-load current C) No greater than 200 % of the motor’s full-load current D) No more than 250 % of the motor’s full-load current Answer: D Explanation: NEC 430.32 permits an overload fuse up to 250 % of the motor’s full-load current.
Contractor Ultimate Exam
A) 40 A
B) 45 A
C) 50 A
D) 60 A
Answer: C Explanation: NEC 422.13 requires the overcurrent device to be not less than 125 % of the water heater’s rating, so a 45-A heater needs a 50-A breaker. Question 49. The NEC permits the use of a single-pole breaker to protect a 240 - V, 2-wire circuit only if: A) The circuit supplies a single-phase motor B) The circuit supplies a 120/240-V receptacle C) The circuit supplies a 240-V load with no neutral D) The circuit supplies a 120-V lighting circuit Answer: C Explanation: A single-pole breaker can protect a 240-V, 2-wire (no neutral) circuit because it only disconnects one hot leg; both legs must be tied together via a common trip or handle tie. Question 50. Which NEC article governs the installation of fire alarm wiring? A) Article 300 B) Article 760 C) Article 210 D) Article 430 Answer: B Explanation: Article 760 covers fire alarm systems, including wiring methods and protection. Question 51. The minimum conduit fill for a single 4-AWG THHN conductor is: A) 31 % B) 40 %
Contractor Ultimate Exam
C) 53 %
D) 75 %
Answer: D Explanation: For a single conductor, the fill is limited to 53 % of the conduit’s internal cross-section; however, NEC Table 1, Chapter 9 permits up to 53 % for one conductor. Since the question asks “minimum,” the answer is 53 %; but the provided options include 75 % which is for a single 14-AWG or smaller conductor. The correct answer based on size 4-AWG is 53 %. Therefore, answer C. Question 52. Which of the following is the correct method for grounding a metal raceway that serves as the equipment grounding conductor? A) Ground the raceway at each outlet box only B) Install a grounding strap within 12 in. of each box C) Bond the raceway to the service grounding electrode at the service entrance only D) No additional bonding is required if the raceway is continuous Answer: B Explanation: NEC 250.118 requires bonding straps within 12 in. of each box when the raceway serves as the EGC. Question 53. A 120/240-V, 3-wire service for a mobile home requires a disconnecting means that must be: A) A 2-pole breaker with a separate neutral disconnect B) A 2-pole breaker with a built-in neutral disconnect C) A 3-pole breaker D) A fusible switch only Answer: B Explanation: Mobile home services must have a 2-pole breaker that also disconnects the neutral (NEC 230.71). Question 54. The minimum burial depth for a 4-AWG copper grounding electrode conductor installed in direct burial is: A) 12 in.
Contractor Ultimate Exam
D) No special protection required Answer: B Explanation: NEC 210.8(A)(6) requires GFCI protection for kitchen countertop receptacles. Question 58. When using MC cable in a wet location, the cable must be: A) Listed for wet locations B) Installed in conduit only C) Covered with a waterproof jacket D) Replaced with UF cable Answer: A Explanation: MC cable must be listed for wet locations (e.g., MC-WT) to be used directly in such environments. Question 59. The maximum number of conductors allowed in a 1-in. EMT without exceeding the 40 % fill limit is: A) 8 B) 12 C) 16 D) 20 Answer: B Explanation: Using Table 1, Chapter 9, a 1-in. EMT has an internal area of 0.860 in². Forty-percent fill is 0.344 in². A 12-AWG THHN has an area of 0.0133 in², so 0.344 / 0.0133 ≈ 25 conductors. However, the 40 % limit is for more than two conductors; the actual answer depends on the conductor size. Since the question does not specify size, the safest answer is B (12) as a typical maximum for mixed sizes. Question 60. For a 250-V, three-phase motor rated 10 HP, the full-load current is approximately: A) 12 A B) 23 A
Contractor Ultimate Exam
C) 35 A
D) 48 A
Answer: B Explanation: Approximate FLC = (HP × 746) / (√3 × V × efficiency). Assuming 90 % efficiency: (10 × 746) / (1.732 × 250 × 0.9) ≈ 23 A. Question 61. A VFD installed in a commercial building must be protected against voltage surges by: A) A standard breaker only B) Surge protective device (SPD) listed for the VFD C) A fuse rated at 150 % of VFD current D) No additional protection is required Answer: B Explanation: NEC 430.101 requires VFDs to have an SPD listed for the equipment. Question 62. Which of the following is a permissible method for extending a grounding electrode system? A) Using a 12-AWG copper conductor tied to the water pipe only B) Connecting a grounding electrode conductor to a metal underground storage tank C) Running a 4-AWG aluminum conductor without a bonding jumper D) Using a flexible metal conduit without a bonding strap Answer: B Explanation: Metal underground tanks are acceptable grounding electrodes (NEC 250.52(A)(3)). Question 63. In a Class II, Division 1 hazardous location, which wiring method is acceptable for power circuits? A) PVC conduit only B) Rigid metal conduit (RMC) with proper fittings C) NM-B cable in conduit
