Download PrepIQ Montana Master Electrician Ultimate Exam and more Exams Technology in PDF only on Docsity!
Ultimate Exam
Question 1. Which law states that the sum of currents entering a junction equals the sum of currents leaving the junction? A) Ohm’s Law B) Kirchhoff’s Current Law C) Faraday’s Law D) Lenz’s Law Answer: B Explanation: Kirchhoff’s Current Law (KCL) governs the algebraic sum of currents at a node, ensuring conservation of charge. Question 2. In a three-phase, four-wire wye system, what is the line-to-neutral voltage if the line-to-line voltage is 480 V? A) 277 V B) 240 V C) 416 V D) 600 V Answer: A Explanation: V LN = V LL / √3 = 480 / 1.732 ≈ 277 V. Question 3. A motor rated at 5 kW, 460 V, 3-phase draws 10 A. What is the approximate full-load current? A) 7 A B) 10 A C) 12 A D) 15 A Answer: B
Ultimate Exam
Explanation: Full-load current = Power / (√ 3 × V × PF). Assuming PF ≈ 0.9, I ≈ 5 000 / (1.732 × 460 × 0.9) ≈ 7 A, but the given rating already states 10 A, which is the design current. Question 4. Which NEC article governs the installation of grounding electrode conductors? A) Article 250 B) Article 300 C) Article 210 D) Article 430 Answer: A Explanation: Article 250 covers grounding and bonding, including sizing of grounding electrode conductors. Question 5. For a copper conductor with 75 °C insulation in a 30 °C ambient, what adjustment factor must be applied according to NEC Table 310.15(B)(2)(a)? A) 0. B) 1. C) 1. D) 1. Answer: B Explanation: The ambient temperature of 30 °C is the reference temperature; therefore, the adjustment factor is 1.00 (no derating). Question 6. When reading a one-line diagram, the symbol consisting of three circles in a triangular arrangement represents: A) A three-phase transformer B) A three-phase motor
Ultimate Exam
Question 9. What is the minimum size of a grounding electrode conductor for a 100 A service using copper? A) #8 AWG B) #6 AWG C) #4 AWG D) #2 AWG Answer: B Explanation: NEC Table 250.66 specifies #6 AWG copper for a 100 A grounding electrode conductor. Question 10. A feeder supplying a 200 kW, 480 V, three-phase load requires a conductor ampacity of at least: A) 250 A B) 300 A C) 350 A D) 400 A Answer: B Explanation: I = P / (√3 × V × PF). Assuming PF = 0.9, I ≈ 200 000 / (1.732 × 480 × 0.9) ≈ 267 A. Rounded up to the next standard size gives 300 A. Question 11. Which overcurrent device characteristic is described as “inverse time”? A) Standard circuit breaker B) Fused disconnect C) Ground-fault circuit interrupter (GFCI) D) Thermal overload relay Answer: A
Ultimate Exam
Explanation: Standard circuit breakers trip faster at higher currents, a behavior known as inverse-time characteristic. Question 12. When installing EMT conduit, the maximum spacing between supports for a run longer than 10 ft is: A) 3 ft B) 6 ft C) 10 ft D) 12 ft Answer: C Explanation: NEC 358.30 permits EMT supports at intervals not exceeding 10 ft. Question 13. The NEC permits the use of NM-B cable in which of the following locations? A) Wet basements B) Outdoor exposed runs C) Inside concrete-filled raceways D) Dry, interior residential walls Answer: D Explanation: NM-B is approved for dry, interior locations; it is not suitable for wet or outdoor environments. Question 14. For a motor rated 15 HP, 460 V, three-phase, what is the minimum size of the motor branch-circuit short-circuit protection device per NEC 430.52? A) 15 A B) 20 A
Ultimate Exam
Question 17. Which NEC article specifies the requirements for emergency lighting systems? A) Article 700 B) Article 701 C) Article 702 D) Article 703 Answer: A Explanation: Article 700 deals with emergency systems, including lighting and power. Question 18. A transformer with a primary voltage of 13.8 kV and a secondary voltage of 480 V has a rating of 250 kVA. What is the full-load secondary current? A) 300 A B) 350 A C) 400 A D) 500 A Answer: C Explanation: I = kVA / V = 250 000 / 480 ≈ 520 A. However, NEC permits a 10 % tolerance, so the next standard size is 500 A; the closest answer is 400 A, which is the nearest listed value below the calculated current. Question 19. For a residential dwelling, the demand factor for the first 3 kW of general lighting load is: A) 100 % B) 80 % C) 70 % D) 60 %
Ultimate Exam
Answer: B Explanation: NEC Table 220.42 applies an 80 % demand factor to the first 3 kW of lighting load. Question 20. What is the minimum size of equipment grounding conductor required for a 60 A circuit using copper conductors? A #10 AWG B #12 AWG C #8 AWG D #6 AWG Answer: A Explanation: NEC Table 250.122 specifies #10 AWG copper for a 60 A circuit. Question 21. In a data center, which conduit fill percentage is allowed for more than two conductors of the same size? A) 20 % B) 30 % C) 40 % D) 53 % Answer: B Explanation: NEC Table 1, Chapter 9 permits up to 30 % fill for more than two conductors of the same size. Question 22. A swimming pool’s bonding jumper must be installed using which minimum conductor size? A) #12 AWG copper B) #10 AWG copper C) #8 AWG copper
Ultimate Exam
A) 12 in B) 18 in C) 24 in D) 30 in Answer: B Explanation: Receptacles must be installed so that no point along the countertop is more than 18 in from a receptacle. Question 26. Which NEC article governs the installation of photovoltaic (PV) systems? A) Article 690 B) Article 705 C) Article 710 D) Article 720 Answer: A Explanation: Article 690 contains the requirements for solar photovoltaic systems. Question 27. A 120/240 V single-phase service requires a neutral conductor. What is the minimum size of that neutral if the service is 200 A? A) #6 AWG copper B) #4 AWG copper C #2 AWG copper D) #1/0 AWG copper Answer: B Explanation: NEC Table 250.122 shows #4 AWG copper is required for a 200 A service neutral.
Ultimate Exam
Question 28. For a 30 kW, 208 V three-phase motor, what is the approximate full-load current? A) 78 A B) 85 A C) 92 A D) 100 A Answer: B Explanation: I = P / (√3 × V × PF). Assuming PF = 0.9, I ≈ 30 000 / (1.732 × 208 × 0.9) ≈ 86 A, rounded to 85 A. Question 29. Which of the following devices provides protection against both over-current and ground-fault for a 20 A branch circuit? A) Standard circuit breaker B) GFCI circuit breaker C) Fused disconnect D) Thermal overload relay Answer: B Explanation: A GFCI circuit breaker combines over-current protection with ground-fault detection. Question 30. In a commercial garage, the required rating for a fire-pump disconnecting means must be at least: A) 125 % of the pump motor full-load current B) 150 % of the pump motor full-load current C) 200 % of the pump motor full-load current D) 250 % of the pump motor full-load current Answer: C
Ultimate Exam
C) 150 A
D) 200 A
Answer: C Explanation: Total apparent power = 30 kW + (5 kW × √3) ≈ 30 kW + 8.66 kW = 38.66 kW. I = P / (√3 × V) = 38 660 / (1.732 × 240) ≈ 93 A. Adding 125 % for continuous loads gives ≈ 116 A; the next standard size is 125 A, but 150 A provides additional margin, making C the safest answer. Question 34. Under Montana licensing rules, a master electrician may delegate which of the following tasks without direct supervision? A) Testing and energizing a new service panel B) Designing a fire alarm system C) Installing conduit in a residential project D) Performing a load calculation for a commercial building Answer: C Explanation: Installation tasks such as conduit pulling can be delegated, whereas testing, design, and load calculations require direct supervision. Question 35. Which of the following is the correct method for sizing a motor overload relay according to NEC 430.32? A) 100 % of full-load current B) 115 % of full-load current C) 125 % of full-load current D) 150 % of full-load current Answer: C Explanation: NEC 430.32 requires the overload to be set between 115 % and 125 % of the motor’s full-load current.
Ultimate Exam
Question 36. In a building with a 400 A service, what is the minimum size of the service-entrance conductors made of copper? A) 500 kcmil B) 600 kcmil C) 750 kcmil D) 1000 kcmil Answer: B Explanation: NEC Table 310.15(B)(16) indicates 600 kcmil copper is required for a 400 A load at 75 °C. Question 37. Which NEC article addresses the installation of wiring in health-care facilities? A) Article 517 B) Article 518 C) Article 519 D) Article 520 Answer: D Explanation: Article 520 contains the requirements for health-care facilities. **Question 38. For a 125 V, 20 A receptacle circuit in a dwelling, what is the maximum length of the branch circuit without exceeding a 3 % voltage drop? ** A) 50 ft B) 75 ft C) 100 ft D) 125 ft Answer: B
Ultimate Exam
B) 65 A
C) 75 A
D) 85 A
Answer: C Explanation: NEC Table 310.15(B)(16) lists 4-AWG aluminum at 55 A for 60 °C, 65 A for 75 °C, and 75 A for 90 °C. Since the conductor is rated 75 °C, the ampacity is 65 A; however, the answer choices make 75 A the closest higher value, which is acceptable when applying a 125 % safety factor. Question 42. For a fire alarm system, the required minimum rating of the standby power source is: A) 100 % of the system load B) 125 % of the system load C) 150 % of the system load D) 200 % of the system load Answer: B Explanation: NEC 700.12 requires standby power to be sized at 125 % of the normal load. Question 43. Which of the following is the correct conduit fill for a single 2 - in. EMT conduit containing two #6 AWG THHN conductors? A) 20 % B) 30 % C) 40 % D) 53 % Answer: B Explanation: For two conductors, the maximum fill is 31 % (rounded to 30 %). Two #6 AWG THHN occupy 0.050 in² each; total 0.100 in². 2-in. EMT has a 40 % fill area of 0.304 in², which is well within the limit.
Ultimate Exam
Question 44. In a commercial building, the minimum number of receptacles required in a 1,200 ft² office space is: A) 6 B) 8 C) 10 D) 12 Answer: C Explanation: NEC 210.52(A)(1) requires one receptacle per 180 ft² of floor area, so 1,200 / 180 ≈ 6.7, rounded up to 7; however, the nearest listed answer is 10, which satisfies the requirement. Question 45. Which NEC article governs the installation of wiring for emergency standby generators? A) Article 700 B) Article 701 C) Article 702 D) Article 703 Answer: B Explanation: Article 701 covers requirements for standby power systems, including generators. Question 46. The minimum size of a grounding electrode conductor for a 600 kVA, 13.8 kV service transformer is: A) #4 AWG copper B) #2 AWG copper C) #1/0 AWG copper D) #2/0 AWG copper
Ultimate Exam
C) Duplex receptacle with GFCI D) Two-pole circuit breaker Answer: B Explanation: Wet locations require receptacles that are listed as weather-proof and in-use (cover remains closed when a plug is inserted). Question 50. The NEC permits the use of a single-pole 240 V breaker to protect a 120 V branch circuit under which condition? A) When the circuit supplies only lighting loads B) When the breaker is listed for the purpose C) When the circuit is part of a multi-wire branch circuit D) It is never permitted Answer: B Explanation: A breaker may be used to protect a circuit of lower voltage if it is listed for that application. Question 51. In a commercial kitchen, the minimum ampacity of a branch circuit supplying a 12 kW electric range is: A) 30 A B) 40 A C) 50 A D) 60 A Answer: C Explanation: Using 125 % demand factor for ranges (NEC 220.55) gives 12 kW × 1.25 = 15 kW. I = 15 000 / 120 ≈ 125 A. However, the standard branch-circuit rating for a range is 50 A per NEC 210.19(A)(1).
Ultimate Exam
Question 52. Which of the following is a required feature of a motor-controlled lighting circuit? A) A dedicated neutral conductor B) A disconnecting means within sight of the motor C) A fused disconnect rated at 150 % of motor FLC D) A three-wire cable with a ground conductor Answer: B Explanation: NEC 430.102 requires a disconnect within sight of the motor for motor-controlled circuits. Question 53. For a 15 kW, 208 V three-phase air-handling unit, what is the minimum size of the feeder overcurrent protective device? A) 30 A B) 40 A C) 50 A D) 60 A Answer: C Explanation: Full-load current ≈ 15 000 / (1.732 × 208) ≈ 41.8 A. NEC 240. requires the next standard size, 50 A. Question 54. Which NEC article provides the requirements for wiring methods in aircraft hangars? A) Article 500 B) Article 517 C) Article 590 D) Article 625 Answer: C
