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Master Electrician Exam (NEC) practice questions

200 free questions with answers and explanations.

Practice test
  1. 101.A master electrician is troubleshooting a resistive heating element in a 240V AC circuit. An ammeter measures 15A flowing through the element. What is the approximate power consumed by the heating element?General Electrical Knowledge
  2. 102.A branch circuit supplies a continuous commercial cooking load of 10kW at 208V, 3-phase. The circuit conductors are copper, 75°C rated. What is the minimum ampere rating required for the overcurrent protective device (OCPD) for this circuit?Services, Feeders, and Branch Circuits
  3. 103.A commercial building has a 208Y/120V, 3-phase, 4-wire service. The calculated load for the service is 150A. The service entrance conductors are copper, installed in RMC, and rated for 75°C. What is the minimum size of the grounded (neutral) conductor required if there are no nonlinear loads and the maximum unbalanced load is 100A?Services, Feeders, and Branch Circuits
  4. 104.A manufacturing plant is installing a new feeder for a 75 HP, 480V, 3-phase squirrel-cage motor with a design letter F. The motor's full-load current (FLC) from NEC Table 430.250 is 96A. What is the minimum continuous current rating required for the inverse-time circuit breaker used for short-circuit and ground-fault protection for this motor feeder?Services, Feeders, and Branch Circuits
  5. 105.A residential kitchen requires a 20A, 120V small-appliance branch circuit. How many such circuits are required by the NEC for the kitchen area, excluding circuits for specific appliances like refrigerators or dishwashers?Services, Feeders, and Branch Circuits
  6. 106.A large industrial facility has a 400A, 480Y/277V, 3-phase, 4-wire service. The service entrance conductors are 600 kcmil copper. The service equipment consists of a main circuit breaker and a panelboard. What is the maximum size of the main bonding jumper required for this service?Services, Feeders, and Branch Circuits
  7. 107.A circuit for a 3-phase, 480V, 20 HP motor requires a feeder. The motor has a full-load current (FLC) of 27A. The feeder conductors are copper, installed in conduit, and rated for 75°C. What is the minimum required ampacity for the feeder conductors supplying this motor?Services, Feeders, and Branch Circuits
  8. 108.A new commercial building requires a 200A, 120/240V, single-phase service. The service entrance conductors will be run in RMC and have an ampacity of 200A. What is the minimum size copper grounding electrode conductor (GEC) required if the largest service-entrance ungrounded conductor is 3/0 AWG copper?Services, Feeders, and Branch Circuits
  9. 109.A commercial kitchen is being wired with a 480Y/277V, 3-phase, 4-wire service. The service entrance conductors are 500 kcmil copper per phase. What is the minimum size copper bonding jumper required to bond the service raceway to the service equipment enclosure?Services, Feeders, and Branch Circuits
  10. 110.A master electrician is installing a 120V, 15A branch circuit for general-purpose receptacles in a dwelling unit. The circuit is protected by a 15A circuit breaker. Which of the following statements regarding the receptacle outlet requirements is correct?Services, Feeders, and Branch Circuits
  11. 111.A detached garage for a dwelling unit is supplied by a 60A feeder from the main house panel. The feeder consists of four insulated copper conductors (two ungrounded, one grounded, and one equipment grounding conductor) in a single conduit. The conductors are 6 AWG copper, rated for 75°C. What is the minimum size required for the equipment grounding conductor (EGC) for this feeder?Services, Feeders, and Branch Circuits
  12. 112.A commercial office space has a 120/208V, 3-phase, 4-wire panelboard. The panelboard has a main circuit breaker rated for 225A. The calculated demand load for the panelboard is 180A. What is the minimum required rating for the panelboard busbars?Services, Feeders, and Branch Circuits
  13. 113.A residential dwelling unit is being constructed with a 200A, 120/240V single-phase service. The service entrance conductors are 250 kcmil aluminum. What is the minimum continuous current rating required for the main service overcurrent device?Services, Feeders, and Branch Circuits
  14. 114.A commercial building has a 400A, 480Y/277V, 3-phase, 4-wire service. The service entrance conductors are 500 kcmil copper. What is the minimum size copper equipment grounding conductor required for a feeder supplying a 100A panelboard from the main service switchboard?Services, Feeders, and Branch Circuits
  15. 115.A technician is installing a 20A, 120V general-purpose branch circuit for a dwelling unit. The circuit conductors are 12 AWG copper. What is the maximum number of 15A, 120V duplex receptacles that can be connected to this circuit, assuming no other loads?Services, Feeders, and Branch Circuits
  16. 116.A residential dwelling unit requires a new 200A, 120/240V, single-phase service. The service entrance conductors will be 3/0 AWG copper with THWN-2 insulation. The service raceway is 2-inch rigid metal conduit (RMC) and passes through a concrete slab before terminating in the service equipment. What is the minimum size of the concrete-encased electrode required, if used as the sole grounding electrode?Services, Feeders, and Branch Circuits
  17. 117.A utility company is providing a 600A, 480Y/277V, 3-phase, 4-wire service to a new commercial building. The service entrance conductors are two sets of 400 kcmil copper per phase. What is the minimum size copper main bonding jumper required?Services, Feeders, and Branch Circuits
  18. 118.A commercial building has a 400A, 480Y/277V, 3-phase, 4-wire service. The utility requires the service equipment to be located outdoors. The main service disconnect is rated for 400A. What is the maximum distance, in feet, that the service entrance conductors are permitted to run inside the building from the point of entrance to the main service disconnect, without additional protection?Services, Feeders, and Branch Circuits
  19. 119.A commercial building has a 208Y/120V, 3-phase, 4-wire service. The calculated load for the service is 300A. The service entrance conductors are 350 kcmil copper. What is the minimum size copper main bonding jumper required?Services, Feeders, and Branch Circuits
  20. 120.A commercial building requires a 120/208V, 3-phase, 4-wire service. The calculated demand load for the service is 150A. What is the minimum size copper service entrance conductor required for this service, assuming THWN insulation?Services, Feeders, and Branch Circuits
  21. 121.A technician is installing a 120V, 20A branch circuit for a bathroom receptacle in a dwelling unit. The circuit will serve only the bathroom receptacle. What is the minimum conductor size required for the ungrounded and grounded conductors, assuming THHN insulation and copper conductors?Services, Feeders, and Branch Circuits
  22. 122.A master electrician is installing a 3-phase, 480V, 50 HP squirrel-cage motor. The motor has a full-load current (FLA) of 65A. The circuit will use 75°C rated conductors. What is the minimum size copper feeder conductor required for this motor?Services, Feeders, and Branch Circuits
  23. 123.A master electrician is installing a 100A, 120/240V single-phase service for a dwelling unit. The service entrance conductors are 2 AWG copper. If the service is supplied by overhead conductors and the point of attachment is 15 feet above finished grade, what is the minimum clearance required for the service drop conductors over a public street?Services, Feeders, and Branch Circuits
  24. 124.A master electrician is installing a new 100A, 120/240V, single-phase service for a dwelling unit. The service raceway is 1 1/4-inch PVC conduit. The service drop conductors are 2 AWG aluminum. What is the minimum vertical clearance required for the service drop conductors over a residential driveway that is not accessible to commercial vehicles?Services, Feeders, and Branch Circuits
  25. 125.A newly constructed commercial kitchen requires two 20A, 120V small-appliance branch circuits to serve the countertop receptacles in the kitchen area. How many such circuits are required by the NEC for these specific receptacles?Services, Feeders, and Branch Circuits
  26. 126.A commercial building requires a 400A, 480Y/277V, 3-phase, 4-wire service. The service entrance conductors are 500 kcmil copper. What is the minimum size grounded (neutral) conductor required for this service, assuming the maximum unbalanced load is 250A and there are no nonlinear loads?Services, Feeders, and Branch Circuits
  27. 127.A master electrician is installing new service entrance conductors for a dwelling unit. The service is 200A, 120/240V, single-phase. The service entrance conductors are 2/0 AWG copper with THWN insulation. What is the minimum size aluminum grounded conductor (neutral) required for this service?Services, Feeders, and Branch Circuits
  28. 128.A large industrial facility requires a 1000A, 480Y/277V, 3-phase, 4-wire service. The service entrance conductors are three sets of 500 kcmil copper per phase. What is the minimum size copper grounding electrode conductor (GEC) required if the grounding electrode is a metal underground water pipe electrode?Services, Feeders, and Branch Circuits
  29. 129.A commercial office space requires a new 20A, 120V branch circuit for receptacle outlets. The circuit conductors will be 12 AWG copper with 75°C insulation, and the overcurrent protective device (OCPD) is a 20A circuit breaker. The connected load is 16A continuous. What is the maximum continuous load permitted on this circuit, considering the OCPD and conductor ratings?Services, Feeders, and Branch Circuits
  30. 130.A commercial building has a 600A, 480Y/277V, 3-phase, 4-wire service. The service equipment includes a main service disconnect and an individual meter socket. Which of the following is considered a service point?Services, Feeders, and Branch Circuits
  31. 131.A residential dwelling unit is being constructed with a 200A, 120/240V single-phase service. The service entrance conductors are 3/0 AWG copper. What is the minimum size copper grounding electrode conductor (GEC) required if the grounding electrode is a concrete-encased electrode?Services, Feeders, and Branch Circuits
  32. 132.A residential dwelling unit requires a 100A, 120/240V single-phase service. The service entrance conductors are 2 AWG copper. What is the minimum size copper grounding electrode conductor (GEC) required if a ground rod is the sole grounding electrode?Services, Feeders, and Branch Circuits
  33. 133.A convenience store is being wired with a 208Y/120V, 3-phase, 4-wire service. The calculated load for the service is 300A. The service entrance conductors are 350 kcmil copper with THWN insulation. What is the minimum size copper service grounded conductor (neutral) required?Services, Feeders, and Branch Circuits
  34. 134.A master electrician is installing a new 200A, 120/240V single-phase service for a dwelling unit. The service entrance conductors are 3/0 AWG copper. What is the minimum size copper equipment grounding conductor required for the service?Services, Feeders, and Branch Circuits
  35. 135.A technician is installing a 20A, 120V general-purpose branch circuit for a dwelling unit. The circuit will supply multiple receptacle outlets. What is the minimum continuous ampacity required for the branch-circuit conductors, assuming 75°C terminals and continuous loads?Services, Feeders, and Branch Circuits
  36. 136.A manufacturing facility is installing a new 20 HP, 480V, 3-phase squirrel-cage induction motor. The motor has a nameplate full-load current rating of 27A. What is the maximum inverse-time circuit breaker rating permitted for branch-circuit short-circuit and ground-fault protection for this motor, assuming it does not exceed the controller's short-circuit rating?Services, Feeders, and Branch Circuits
  37. 137.A utility company is providing a 600A, 480Y/277V, 3-phase, 4-wire service to a new commercial building. The service drop conductors from the utility pole to the service point on the building are installed over a public street. What is the minimum vertical clearance required for the service drop conductors above the public street?Services, Feeders, and Branch Circuits
  38. 138.A commercial kitchen is being renovated, and a new 208Y/120V, 3-phase, 4-wire feeder is being installed from the main service panel to a subpanel in the kitchen. The feeder is protected by a 100A overcurrent device. What is the minimum size copper equipment grounding conductor required for this feeder?Services, Feeders, and Branch Circuits
  39. 139.A master electrician is installing a new 200A, 120/240V single-phase service for a dwelling unit. The service entrance conductors are 3/0 AWG copper. What is the minimum size required for the main bonding jumper if it is a wire type?Services, Feeders, and Branch Circuits
  40. 140.A commercial building requires a 120/208V, 3-phase, 4-wire service. The calculated demand load for the ungrounded conductors is 250A. What is the minimum continuous ampacity required for the service entrance conductors, assuming they serve continuous loads?Services, Feeders, and Branch Circuits
  41. 141.A master electrician is installing a new 400A, 480Y/277V, 3-phase, 4-wire service. The service entrance conductors are 600 kcmil copper, installed in parallel in two raceways. What is the minimum size required for the main bonding jumper if it is a wire type?Services, Feeders, and Branch Circuits
  42. 142.A commercial building has a 400A, 480Y/277V, 3-phase, 4-wire service. The service entrance conductors are 500 kcmil copper. What is the minimum size required for the service grounded conductor?Services, Feeders, and Branch Circuits
  43. 143.A master electrician is installing a new 20A, 120V branch circuit for a bathroom receptacle in a dwelling unit. The circuit conductors will be 12 AWG copper with 75°C insulation. What is the maximum continuous load permitted on this circuit?Services, Feeders, and Branch Circuits
  44. 144.A residential garage is being built detached from the main dwelling unit. It will be supplied by a 60A feeder from the main house panel. The garage has a grounding electrode system consisting of two ground rods. What is the minimum size required for the grounding electrode conductor (GEC) from the garage subpanel to these ground rods?Services, Feeders, and Branch Circuits
  45. 145.A residential dwelling unit is being constructed with a 200A, 120/240V single-phase service. The service entrance conductors are 3/0 AWG copper. What is the minimum size required for the grounding electrode conductor (GEC) if the grounding electrode is a ground rod?Services, Feeders, and Branch Circuits
  46. 146.A master electrician is installing a new 200A, 120/240V, single-phase service for a residential dwelling. The service entrance conductors are 2/0 AWG copper. The grounding electrode system consists of a metal underground water pipe and a ground rod. What is the minimum size copper grounding electrode conductor required to connect to the metal underground water pipe electrode?Grounding and Bonding
  47. 147.A master electrician is installing a new 480Y/277V, 3-phase, 4-wire service for a commercial building. The service conductors are 500 kcmil copper. What is the minimum size copper grounding electrode conductor (GEC) required to connect to a concrete-encased electrode?Grounding and Bonding
  48. 148.A farm building has a 5 hp, three-phase, 230V motor for irrigation, a 10 kW electric water heater, and 500 VA of general lighting. What is the minimum calculated demand load for the farm building service, excluding the farm dwelling, according to NEC 220.102?Load Calculations
  49. 149.A master electrician is installing a new 200A, 120/240V, single-phase service for a dwelling unit. The service entrance conductors are 3/0 AWG copper. What is the minimum size required for the main bonding jumper (MBJ) if it is copper?Services, Feeders, and Branch Circuits
  50. 150.A master electrician is installing a new 200A, 208Y/120V service for a commercial building. According to NEC 250.24(C)(1), what is the minimum size required for the grounded (neutral) conductor for this service?General Electrical Knowledge