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Journeyman Electrician Exam (NEC) practice questions

215 free questions with answers and explanations.

Practice test
  1. 151.A residential electrician is installing a new 120-volt, 15-amp branch circuit for a bedroom using NM cable. What is the minimum size copper conductor required for this circuit, assuming it is not part of a bundle exceeding 24 inches in length and the ambient temperature is 30°C (86°F)?Wiring Methods and Materials
  2. 152.A motor control circuit uses a 120V AC supply. The control circuit conductors are installed in a raceway and are protected by a 15A overcurrent protective device. According to NEC 430.72(A), what is the minimum gauge (AWG) permitted for these control circuit conductors if they do not extend beyond the control enclosure?Control Devices and Motors
  3. 153.A licensed electrician is installing a new 200-amp service entrance for a commercial building. The service conductors will be routed through a raceway. According to NEC, what is the minimum size copper grounding electrode conductor (GEC) required for a service with ungrounded service conductors of 250 kcmil each?Wiring Methods and Materials
  4. 154.A motor control circuit uses a control transformer to step down 480V to 120V for the control power. The control transformer has a primary overcurrent protective device rated at 2.5A. The transformer's primary impedance is 5%. According to NEC 430.72(C), what is the maximum rating permitted for the primary overcurrent protective device when secondary overcurrent protection is not provided?Control Devices and Motors
  5. 155.A residential electrician is installing a new 20-amp, 120-volt branch circuit in a dwelling. The cable will pass through bored holes in wood studs. According to NEC 300.4(A)(1), what is the minimum distance the edge of the bored hole must be from the nearest edge of the wood member to avoid the need for protection by a steel plate or bushing?Wiring Methods and Materials
  6. 156.A commercial electrician is installing a new 480-volt, 3-phase motor feeder in a wet location. The feeder consists of 3/0 AWG THWN-2 copper conductors. What is the minimum allowable bend radius for 1-1/2 inch Rigid Metal Conduit (RMC) with these conductors, assuming a field bend without a one-shot bender?Wiring Methods and Materials
  7. 157.An electrician is installing a new 20-amp, 120-volt circuit for a dedicated refrigerator outlet in a commercial kitchen. The circuit will pass through a 2-hour fire-rated wall. What is the minimum fire rating required for the firestop system used to seal the penetration around the raceway?Wiring Methods and Materials
  8. 158.A commercial building requires a new 208-volt, 3-phase, 60-amp feeder circuit to a subpanel located 75 feet away. The circuit will use three 6 AWG THWN copper conductors for the phase conductors and one 10 AWG THWN copper conductor for the equipment grounding conductor. What is the minimum size of the equipment grounding conductor required for this feeder circuit?Wiring Methods and Materials
  9. 159.A residential electrician is installing a new 200-amp, 120/240-volt single-phase service entrance. The grounding electrode conductor (GEC) will connect to a ground rod. What is the minimum size for the GEC when connected to a ground rod, assuming the service conductors are 3/0 AWG copper?Wiring Methods and Materials
  10. 160.A 10 hp, 230V, three-phase motor is used in a continuous duty application. The motor is protected by an inverse-time circuit breaker for short-circuit and ground-fault protection. According to NEC Table 430.250, the FLC for a 10 hp, 230V, three-phase motor is 28A. What is the maximum allowable setting for the inverse-time circuit breaker, assuming the motor's starting current would not be sufficient to trip it at this setting?Control Devices and Motors
  11. 161.A commercial electrician is installing a new 20-amp, 120-volt branch circuit in a suspended ceiling. The circuit will use Type MC cable. What is the maximum distance the MC cable can be supported from a box or fitting where it terminates?Wiring Methods and Materials
  12. 162.A client is upgrading an existing motor control system for a 15 hp, 460V, three-phase motor. The existing system uses a mechanical contactor. The client wants to reduce maintenance and increase the lifespan of the control components. Which of the following devices would be most suitable to replace the mechanical contactor for switching the motor's power circuit?Control Devices and Motors
  13. 163.A 50 hp, 460V, three-phase motor is controlled by a full-voltage non-reversing (FVNR) starter. The motor nameplate indicates a service factor (SF) of 1.15. According to NEC Table 430.250, the motor's full-load current (FLC) is 65A. What is the maximum continuous current rating permitted for the motor's thermal overload protective device?Control Devices and Motors
  14. 164.An industrial electrician is installing a new control circuit in a hazardous location identified as Class II, Division 1. Which of the following wiring methods is generally permitted for this application?Wiring Methods and Materials
  15. 165.A technician is installing a new 200-amp, 240-volt single-phase feeder to a detached garage. The feeder consists of three 3/0 AWG copper conductors (two ungrounded, one neutral). What is the minimum size copper equipment grounding conductor (EGC) required for this feeder?Wiring Methods and Materials
  16. 166.A three-phase, 20 hp, 480V motor has a nameplate full-load current (FLA) of 27A. According to NEC Table 430.250, the FLC for a 20 hp, 480V, three-phase motor is 27A. What is the minimum continuous current rating required for the motor controller for this motor?Control Devices and Motors
  17. 167.A residential electrician is installing a new 200-amp, 120/240-volt single-phase service entrance for a single-family dwelling. The service conductors are 3/0 AWG copper. What is the minimum size copper grounding electrode conductor (GEC) required if the grounding electrode is a ground rod?Wiring Methods and Materials
  18. 168.A commercial building requires a new 208-volt, 3-phase, 60-amp feeder circuit to a subpanel. The circuit will be run using 1 AWG THHN copper conductors. What is the maximum number of current-carrying conductors allowed in a 1-inch trade size Rigid Metal Conduit (RMC) before derating factors must be applied?Wiring Methods and Materials
  19. 169.A technician is installing a new three-phase, 480V motor with a full-load current (FLA) of 65A. The motor is equipped with a separate thermal overload relay. According to NEC 430.32(A)(1), what is the maximum allowable setting for the thermal overload relay if the motor has a service factor of 1.15?Control Devices and Motors
  20. 170.A variable frequency drive (VFD) is used to control a 25 hp, 480V, three-phase motor. The VFD's output conductors to the motor are being sized. The motor has a nameplate FLA of 34A. According to NEC Article 430.122(A), what minimum ampacity is required for the conductors between the VFD and the motor?Control Devices and Motors
  21. 171.A commercial electrician is installing a new 20-amp, 120-volt branch circuit in a suspended ceiling. The circuit is run using Type MC cable. What is the maximum distance the MC cable can be supported from a box or conduit body?Wiring Methods and Materials
  22. 172.A residential electrician is installing a new 120-volt, 15-amp branch circuit for a bedroom. The circuit will use 14 AWG copper conductors. What is the minimum length of free conductor that must be left at each outlet, switch, and junction point for splices or the connection of fixtures or devices?Wiring Methods and Materials
  23. 173.A commercial electrician is installing a new 480-volt, 3-phase motor feeder in a wet location. The feeder consists of 3-inch rigid metal conduit (RMC). What is the minimum radius for a field bend in this RMC, assuming it does not contain lead-sheathed cables?Wiring Methods and Materials
  24. 174.An electrical contractor is installing a new 480-volt, 3-phase motor circuit using 1 AWG THHN copper conductors in a conduit. The circuit passes through a junction box where a splice is made. According to NEC 314.28(A)(2), what is the minimum length of the junction box if it is a straight pull (no offsets or angles)?Wiring Methods and Materials
  25. 175.A residential electrician is installing a new 20-amp, 120-volt branch circuit in a dwelling unit. The circuit will be run through a bored hole in a wood stud. What is the minimum distance required from the nearest edge of the stud to the bored hole for the cable, assuming no steel plate protection is used?Wiring Methods and Materials
  26. 176.A motor circuit requires a disconnecting means capable of opening the circuit to the motor and controller, and it must be lockable in the open position. According to NEC 430.102(A), where must the motor disconnect be located?Control Devices and Motors
  27. 177.A client is installing a new industrial process that requires precise, continuous control of motor speed and torque. The system needs to maintain constant output even with varying load conditions. Which motor control device is best suited for this application?Control Devices and Motors
  28. 178.A residential electrician is installing a new 120-volt, 15-amp branch circuit for a bedroom. The circuit will use 14 AWG copper conductors. What is the minimum size equipment grounding conductor (EGC) required for this circuit?Wiring Methods and Materials
  29. 179.A maintenance technician is replacing a flexible cord on a portable 277-volt industrial machine. The machine requires a grounding conductor. According to NEC 400.22(B), what is the color that must be used for the grounding conductor in a flexible cord?Wiring Methods and Materials
  30. 180.A technician is installing a new 480-volt, 3-phase motor circuit using 4 AWG copper conductors in a conduit. The circuit will supply a motor that draws 80 amps continuous. What is the minimum required temperature rating of the conductor insulation for this application, assuming the conductors are not exposed to temperatures exceeding 30°C (86°F) ambient?Wiring Methods and Materials
  31. 181.A maintenance technician is replacing a flexible cord on a portable 277-volt industrial machine. The machine requires a grounding conductor. What color insulation is typically used for the grounding conductor in a flexible cord for this application, according to NEC?Wiring Methods and Materials
  32. 182.A motor control circuit is designed to operate a 5 hp, 460V, three-phase motor. The control circuit uses a 120V transformer to supply power to the control devices. What type of control scheme typically provides inherent undervoltage protection for the motor?Control Devices and Motors
  33. 183.A commercial electrician is installing a new 20-amp, 120-volt branch circuit in a suspended ceiling. The circuit is run using Type MC cable. What is the maximum distance between supports for the MC cable in a horizontal run?Wiring Methods and Materials
  34. 184.A client requires a motor control system that allows for extremely fine control over the motor's acceleration and deceleration ramps, as well as maintaining precise speed under varying loads. The motor is a 75 hp, 480V, three-phase squirrel cage induction motor. Which control device is best suited for this application?Control Devices and Motors
  35. 185.A residential electrician is installing a new 20-amp, 120-volt branch circuit in a dwelling unit. The circuit is routed through a series of nonmetallic boxes. What is the minimum length of free conductor required at each box for making connections or splices?Wiring Methods and Materials
  36. 186.A technician is troubleshooting a three-phase motor that consistently fails to start, producing only a humming sound, and drawing excessive current. The motor's thermal overloads trip almost immediately. All supply voltages are balanced and correct. Which of the following is the most likely cause of this issue?Control Devices and Motors
  37. 187.An industrial electrician is installing a new control circuit in a hazardous location identified as Class II, Division 1. Which wiring method is generally permitted for this installation, assuming the area is dusty and potentially explosive?Wiring Methods and Materials
  38. 188.A journeyman electrician is installing a new 480-volt, 3-phase, 75 kVA transformer to supply a 208Y/120-volt panel. The transformer primary conductors are protected by fuses. What is the maximum rating of the primary overcurrent protection if the transformer's impedance is less than 6%?Equipment and Devices
  39. 189.A journeyman electrician is installing a 20-ampere branch circuit for general-purpose receptacles in a new dwelling unit garage. How many such branch circuits are minimally required for this garage by the NEC?Equipment and Devices
  40. 190.A technician is installing a 20-ampere, 120-volt general-purpose branch circuit in a commercial building. The circuit will supply receptacles. What is the minimum continuous load permitted on this branch circuit, assuming it is protected by an overcurrent device rated for 100% continuous operation?Equipment and Devices
  41. 191.A journeyman electrician is installing a new 277-volt LED luminaire in a commercial warehouse. The luminaire is rated for a continuous operation of 5.5 amperes. The branch circuit supplying this luminaire is protected by a 20-ampere circuit breaker. What is the minimum continuous load permitted on this branch circuit?Equipment and Devices
  42. 192.A technician is installing a new 120-volt, 15-ampere general-purpose duplex receptacle in a dry location within a dwelling unit. Which NEMA configuration is appropriate for this receptacle?Equipment and Devices
  43. 193.A journeyman electrician is designing an electrical system for a new commercial kitchen. The kitchen includes multiple fixed electric cooking appliances. What is the demand factor that can be applied to four fixed electric cooking appliances rated 4 kW or more each, according to NEC Table 220.55?Equipment and Devices
  44. 194.A journeyman electrician is installing a new 120-volt, 15-ampere general-purpose receptacle in a dwelling unit hallway. What is the minimum required free conductor length that must be left at the outlet box for making connections?Equipment and Devices
  45. 195.A client requests a new 120-volt, 15-ampere duplex receptacle to be installed in a dwelling unit basement, which is not a habitable room. What type of overcurrent protection, if any, is specifically required for this receptacle by the NEC?Equipment and Devices
  46. 196.A technician is troubleshooting a motor control circuit where a limit switch is used to detect the position of a conveyor belt. What is the primary function of this limit switch in the control circuit?Equipment and Devices
  47. 197.A journeyman electrician is installing control wiring for a motor control center. The control circuit conductors are protected by a 15-ampere overcurrent device. What is the minimum allowable ampacity of a No. 18 AWG control circuit conductor, assuming it is insulated with 75°C rated insulation and used for Class 1 control circuits?Equipment and Devices
  48. 198.A journeyman electrician is installing a new 3-phase, 480-volt, 30-horsepower squirrel-cage induction motor. What is the full-load current (FLA) of this motor according to NEC Table 430.250?Equipment and Devices
  49. 199.A journeyman electrician is installing a 300-ampere, 208Y/120-volt service for a commercial building. The service conductors are 3/0 AWG copper with THHN insulation. What is the minimum size grounding electrode conductor (GEC) required if the service entrance conductors are not paralleled?Equipment and Devices
  50. 200.A journeyman electrician is inspecting a new installation of a 400-ampere, 208Y/120-volt service. What is the maximum permitted height of the operating handle of the service disconnecting means when in its highest position?Equipment and Devices