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Certification Guide
Question 1. Ohm’s Law states that voltage equals current multiplied by resistance. If a circuit has a resistance of 50 Ω and a current of 4 A, what is the voltage? A) 12 V B) 200 V C) 54 V D) 250 V Answer: B Explanation: V = I × R = 4 A × 50 Ω = 200 V. Question 2. Watt’s Law for a single‑phase circuit is P = V × I. A 120 V branch circuit supplies a load drawing 15 A. What is the power consumed? A) 1,800 W B) 2,000 W C) 1,500 W D) 2,400 W Answer: A Explanation: P = 120 V × 15 A = 1,800 W. Question 3. In a three‑phase, four‑wire wye system, the line‑to‑neutral voltage is 120 V. What is the line‑to‑line voltage? A) 120 V B) 208 V C) 240 V D) 277 V Answer: B Explanation: V_LL = √3 × V_LN = 1.732 × 120 V ≈ 208 V. Question 4. Which circuit configuration has the same current flowing through all components? A) Series B) Parallel C) Combination D) None of the above Answer: A Explanation: In a series circuit the same current passes through each element. Question 5. In a parallel circuit, if one branch fails open, what happens to the voltage across the remaining branches?
Certification Guide
A) Increases B) Decreases C) Remains the same D) Becomes zero Answer: C Explanation: All parallel branches share the same supply voltage, which is unchanged by an open branch. Question 6. Which symbol on a blueprint represents a single‑pole switch? A) ☐ B) ⏚ C) ⎓ D) ⎔ Answer: A Explanation: A single open rectangle (☐) denotes a single‑pole switch. Question 7. When using a digital multimeter to measure AC voltage, which setting should be selected? A) DC V B) AC V C) Resistance D) Continuity Answer: B Explanation: AC V mode measures alternating‑current voltage. Question 8. A conductor that allows electrons to move freely is called a: A) Insulator B) Semiconductor C) Conductor D) Resistor Answer: C Explanation: Conductors have low resistance and permit free electron flow. Question 9. According to NEC Article 100, “grounded conductor” means: A) The conductor connected to the earth B) The neutral conductor C) The equipment grounding conductor D) Any conductor that is bonded Answer: B
Certification Guide
Explanation: For equipment rated over 420 A, a minimum of 42 in. of clear working space is required. Question 14. The purpose of a grounding electrode system is to: A) Provide a low‑impedance path for fault current to earth B) Carry normal load current C) Isolate the neutral from earth D) Protect against over‑current devices Answer: A Explanation: Grounding electrodes safely dissipate fault currents into the earth. Question 15. According to NEC 250.66, a grounding electrode conductor (GEC) for a service entrance of 200 A must be at least what size? A) 6 AWG B) 8 AWG C) 10 AWG D) 4 AWG Answer: B Explanation: Table 250.66 requires a minimum of 8 AWG copper for a 200 A service. Question 16. Which of the following is NOT a permitted grounding electrode type? A) Ground rod B) Metal water pipe C) Concrete‑encased electrode D) Plastic conduit Answer: D Explanation: Plastic conduit cannot serve as a grounding electrode. Question 17. The equipment grounding conductor (EGC) size is selected based on: A) The ampacity of the circuit‑breaker B) The length of the run C) The voltage rating D) The conduit material Answer: A Explanation: Table 250.122 bases EGC size on the rating of the overcurrent protective device.
Certification Guide
Question 18. For a 20 A breaker, the minimum copper EGC size required is: A) 14 AWG B) 12 AWG C) 10 AWG D) 8 AWG Answer: B Explanation: Table 250.122 specifies 12 AWG copper for 20 A overcurrent devices. Question 19. When installing metal raceways, bonding is required at: A) Both ends B) Only the source end C) Only the load end D) No bonding is required Answer: A Explanation: Metal raceways must be bonded at both ends to ensure equipotential continuity. Question 20. NEC 300.5 requires a minimum burial depth of 24 in. for which type of conduit under residential driveways? A) Rigid metal conduit (RMC) B) Electrical metallic tubing (EMT) C) PVC conduit D) Flexible metal conduit (FMC) Answer: C Explanation: PVC conduit must be buried at least 24 in. under driveways unless protected by concrete. Question 21. The maximum number of conductors allowed in a 4 in.³ junction box for a single‑gate device (each conductor 2 in.³) is: A) 1 B) 2 C) 3 D) 4 Answer: B Explanation: Box fill = volume ÷ conductor fill. 4 in.³ ÷ 2 in.³ = 2 conductors. Question 22. In NEC 310.15(B)(3)(a), the adjustment factor for three current‑carrying conductors in a raceway is:
Certification Guide
Explanation: NEC 430.22 requires conductors to be sized at least 125 % of the motor’s FLC. Question 27. For a 3‑hp, 230 V single‑phase motor, the required overload protection must be set at: A) 115 % of FLC B) 125 % of FLC C) 150 % of FLC D) 200 % of FLC Answer: B Explanation: Overload protection for motors is set at 125 % of the motor’s FLC per NEC 430.32. Question 28. A 30 kVA transformer primary is protected by a 100 A fuse. The secondary is 240 V, 125 A. What is the minimum size of the secondary overcurrent protective device? A) 100 A B) 125 A C) 150 A D) 175 A Answer: B Explanation: The secondary OCPD must be rated at or above the secondary full‑load current (125 A). Question 29. The NEC requires a dedicated 240 V, 30 A circuit for a residential electric water heater. What is the minimum conductor size for copper? A) #10 AWG B) #8 AWG C) #6 AWG D) #4 AWG Answer: B Explanation: 30 A requires at least #10 AWG, but the 125 % rule for continuous loads (water heater) increases the required ampacity to 37.5 A, thus #8 AWG is needed. Question 30. In calculating dwelling unit lighting load, NEC uses 3 VA per square foot. A house of 2,000 ft² therefore requires a minimum lighting load of: A) 4,000 VA B) 5,000 VA C) 6,000 VA D) 7,500 VA Answer: C
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Explanation: 2,000 ft² × 3 VA/ft² = 6,000 VA. Question 31. According to NEC Article 220, the demand factor for the first 10 kW of a dwelling‑unit cooking appliance load is: A) 100 % B) 80 % C) 60 % D) 40 % Answer: B Explanation: NEC Table 220.55 provides a 80 % demand factor for the first 10 kW of cooking appliances. Question 32. For a 100 A service, the optional method of load calculation allows a reduction of: A) 10 % B) 15 % C) 20 % D) 25 % Answer: C Explanation: The optional method (NEC 220.82) permits a 20 % reduction for services 100 A or greater. Question 33. The allowable voltage drop for feeders serving lighting loads is limited to: A) 1 % B) 2 % C) 3 % D) 5 % Answer: B Explanation: NEC recommends a maximum of 2 % voltage drop for feeder circuits. Question 34. A 150 ft run of 12 AWG copper THHN carries 20 A at 120 V. Using K = 12.9, what is the voltage drop? (VD = 2 × K × L × I / CMA) A) 2.6 V B) 3.9 V C) 4.8 V D) 5.2 V Answer: B Explanation: CMA for #12 AWG = 65 MCM. VD = 2 × 12.9 × 150 × 20 / 65 ≈ 3.9 V.
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Answer: B Explanation: OSHA requires a minimum arc rating of 8 cal/cm² for arc‑rated clothing. Question 40. The lockout/tagout (LOTO) procedure requires verification that the equipment is: A) De‑energized B) Grounded C) Ground‑fault cleared D) Insulated Answer: A Explanation: Verification of de‑energization is the final LOTO step. Question 41. OSHA requires trench shoring when the trench depth exceeds: A) 4 ft B) 5 ft C) 6 ft D) 7 ft Answer: B Explanation: OSHA 1926.652 mandates protective systems for trenches deeper than 5 ft. Question 42. According to NFPA 70E, the approach distance for a live part rated 600 V or less is: A) 3 ft B) 4 ft C) 5 ft D) 6 ft Answer: B Explanation: The limited approach distance for 600 V or less is 4 ft. Question 43. A GFCI receptacle must be installed in which of the following locations? A) Unfinished basement B) Kitchen countertop C) Garage wall D) All of the above Answer: D Explanation: GFCI protection is required in all listed locations per NEC 210.8.
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Question 44. A 20‑amp AFCI breaker protects which type of circuit? A) Branch circuits for lighting only B) Any 120 V branch circuit in dwelling units C) Only dedicated appliance circuits D) Only outdoor circuits Answer: B Explanation: NEC 210.12 requires AFCI protection for all 120 V dwelling‑unit branch circuits. Question 45. For a multi‑wire branch circuit (MWBC) sharing a neutral, the breakers must be: A) Single‑pole only B) Ganged or handle‑tied C) Two‑pole of different ratings D) No special requirement Answer: B Explanation: NEC 210.4(B) requires simultaneous disconnect for MWBCs. Question 46. The minimum size of a grounding electrode conductor (GEC) for a 400 A service using copper is: A) #6 AWG B) #4 AWG C) #2 AWG D) #1/0 AWG Answer: C Explanation: Table 250.66 calls for #2 AWG copper for a 400 A service. Question 47. When using conduit as a grounding electrode, the minimum size of the conduit must be: A) 1/2 in. EMT B) 3/4 in. EMT C) 1 in. EMT D) 1 ¼ in. EMT Answer: B Explanation: NEC 250.52(A)(3) permits 3/4 in. EMT as a grounding electrode.
Certification Guide
Question 52. A 120/240 V, 3‑wire split‑phase service requires how many grounded conductors? A) One B) Two C) Three D) None Answer: A Explanation: The neutral is the single grounded conductor in a split‑phase system. Question 53. For a 3‑phase, 4‑wire wye system, the neutral conductor is required when: A) All loads are balanced B) Any single‑phase loads are present C) Only three‑phase loads are used D) The system is 120/208 V only Answer: B Explanation: A neutral provides a return for unbalanced single‑phase loads. Question 54. The NEC permits the use of aluminum conductors for service entrance conductors provided they are: A) 90 °C rated B) 75 °C rated C) 60 °C rated D) Any rating is acceptable Answer: B Explanation: Aluminum service conductors must be rated for at least 75 °C (NEC 310.15(B)(16)). Question 55. When a conductor is installed in a raceway that contains more than three current‑carrying conductors, the ampacity must be multiplied by the adjustment factor found in: A) Table 310.15(B)(3)(a) B) Table 310.12 C) Table 310.15(B)(2)(a) D) Table 310.15(B)(3)(b) Answer: A Explanation: Table 310.15(B)(3)(a) provides the adjustment factors for more than three current‑carrying conductors.
Certification Guide
Question 56. The minimum size of an equipment grounding conductor for a 100 A feeder using copper is: A) #12 AWG B) #10 AWG C) #8 AWG D) #6 AWG Answer: C Explanation: Table 250.122 specifies #8 AWG copper for a 100 A circuit. Question 57. Which NEC article addresses the installation of receptacles in kitchens? A) 210.52 B) 210.52(C) C) 210.52(B) D) 210.52(A) Answer: B Explanation: NEC 210.52(C) specifies the required number and spacing of kitchen countertop receptacles. Question 58. A 30 A, 240 V dryer circuit must be protected by a breaker sized at: A) 20 A B) 30 A C) 35 A D) 40 A Answer: B Explanation: The branch‑circuit OCPD must be rated at or above the dryer’s rated current (30 A). Question 59. The NEC allows a 20 % reduction in the calculated load for a dwelling‑unit service if the total calculated load is greater than: A) 10 kVA B) 15 kVA C) 20 kVA D) 25 kVA Answer: C Explanation: NEC 220.82 permits a 20 % reduction when the calculated load exceeds 20 kVA. Question 60. The required clearances for a panelboard installed in a confined space are increased by: A) 1 ft B) 2 ft C) 3 ft D) 4 ft
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Answer: C Explanation: NEC 210.52(A)(1) requires receptacles in hallways to be no more than 6 ft above the floor; the minimum mounting height is typically 18 in. Question 65. When a circuit supplies both a motor and a lighting load, the branch‑circuit conductor must be sized based on: A) The larger of motor FLC or lighting load B) The sum of motor FLC and lighting load C) 125 % of the motor FLC only D) 100 % of the lighting load only Answer: B Explanation: Conductors must handle the total continuous load; motor FLC is multiplied by 125 % and added to the lighting load. Question 66. A conduit run is 50 ft long, using #4 AWG copper THHN. The conduit is exposed to 40 °C ambient temperature. What is the corrected ampacity? (Base ampacity for #4 AWG is 85 A). A) 78 A B) 80 A C) 85 A D) 90 A Answer: B Explanation: Temperature correction factor at 40 °C for 75 °C conductors is 0.94. 85 A × 0.94 ≈ 80 A. Question 67. The NEC permits the use of a “tap” to connect a branch circuit to a feeder without a separate disconnect if the tap meets: A) 240.15(B) requirements B) 240.21(A) requirements C) 240.21(B) requirements D) 310.15(B)(16) requirements Answer: C Explanation: NEC 240.21(B) allows taps under specific conditions without a separate disconnect.
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Question 68. The term “dead‑front” on a panelboard means: A) The front cover is missing B) No live parts are exposed when the panel is closed C) The panel is de‑energized D) The panel is locked with a padlock Answer: B Explanation: A dead‑front prevents accidental contact with energized components. Question 69. A 300 mm² (≈ 1 /0 AWG) copper conductor is used as a grounding electrode conductor. According to NEC, the maximum length of this GEC without splicing is: A) 50 ft B) 100 ft C) 150 ft D) No limit if continuous Answer: D Explanation: NEC does not limit the length of a continuous grounding electrode conductor. Question 70. Which of the following is NOT a permitted method for grounding a metal water pipe that serves as a grounding electrode? A) Directly clamping the pipe to the GEC B) Using a listed grounding clamp C) Using a non‑listed screw‑type clamp D) Connecting with a listed irreversible connector Answer: C Explanation: Only listed grounding clamps or irreversible connectors are permitted. Question 71. The NEC requires that a receptacle in a laundry area be GFCI‑protected. The minimum ampere rating for this receptacle is: A) 15 A B) 20 A C) 30 A D) 40 A Answer: B Explanation: Laundry receptacles must be 20 A, GFCI‑protected per 210.8(A)(7).
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Question 76. A 240 V, 30 A feeder supplies a 120 V, 20 A subpanel. The feeder must be protected by a breaker sized at: A) 20 A B) 25 A C) 30 A D) 35 A Answer: C Explanation: The feeder OCPD must be at least the ampacity of the feeder, which is 30 A. Question 77. When calculating the load for a dwelling‑unit, the general lighting load is based on: A) 1 VA per ft² B) 2 VA per ft² C) 3 VA per ft² D) 4 VA per ft² Answer: C Explanation: NEC 220.12 uses 3 VA per square foot for general lighting. Question 78. Which of the following is a permissible method for protecting a conduit that is installed outdoors and subject to physical damage? A) Installing in PVC only B) Using metal conduit with a protective cover C) Burying at 12 in. depth D) No protection required Answer: B Explanation: Metal conduit (e.g., EMT, RMC) can be protected with a physical cover for outdoor exposure. Question 79. The NEC requires that a grounding electrode conductor be bonded to the service disconnecting means at which location? A) At the service entrance only B) At the equipment grounding terminal only C) Both at the service entrance and at the equipment grounding terminal D) No bonding required Answer: C Explanation: NEC 250.30 requires bonding at the service equipment and any other equipment grounding terminals.
Certification Guide
Question 80. For a 120/240 V, 3‑wire service, the neutral conductor must be connected to: A) The ground bar only B) The service neutral bar only C) Both ground and neutral bars D) Neither; it floats Answer: B Explanation: The service neutral is connected only to the neutral bus; the ground bus is separate. Question 81. A 45 A, 240 V electric range requires a minimum branch‑circuit breaker size of: A) 40 A B) 45 A C) 50 A D) 60 A Answer: D Explanation: NEC 210.19(A)(1) requires a minimum of 125 % of the range rating: 45 A × 1.25 = 56.25 A → next standard size 60 A. Question 82. Which NEC article governs the installation of fire alarm systems? A) 700 B) 701 C) 702 D) 703 Answer: A Explanation: Article 700 covers emergency systems, including fire alarm wiring. Question 83. The minimum size of a grounding electrode conductor for a 600 A service using aluminum is: A) #2 AWG B) #4 AWG C) #6 AWG D) #8 AWG Answer: B Explanation: Table 250.66 calls for #4 AWG aluminum for a 600 A service.
