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Journeyman Electrician Exam (NEC) practice questions

215 free questions with answers and explanations.

Practice test
  1. 1.A client's existing electrical service blueprint shows a symbol consisting of a circle with a diagonal line through it, crossed by another diagonal line. What does this symbol typically represent?General Electrical Knowledge and Plan Reading
  2. 2.A client reports that a 120V circuit designed for general lighting always trips its 15A overcurrent protective device shortly after being turned on, even though the total connected load (sum of lamp wattages) is only 1200W. All lamps are incandescent. What is the MOST likely cause for the tripping?General Electrical Knowledge and Plan Reading
  3. 3.A technician is installing a new 240V, 10kW electric water heater. The circuit is protected by a 50A overcurrent device. What is the approximate operating current of the water heater at its rated power?General Electrical Knowledge and Plan Reading
  4. 4.A three-phase transformer supplies a balanced resistive load. The line-to-line voltage is 480V, and each phase current is 10A. What is the total apparent power (S) delivered by the transformer?General Electrical Knowledge and Plan Reading
  5. 5.A temporary construction site requires power for portable tools and lighting. The temporary feeder conductors are run overhead. What is the minimum vertical clearance required for these conductors above areas other than public streets, alleys, roads, or driveways, according to NEC?Special Occupancies, Equipment, and Conditions
  6. 6.A client is installing a new electric vehicle (EV) charger in a detached garage. The charger is rated for 48A continuous load. The supply conductors from the main panel in the house to a subpanel in the garage are 75 feet long. Assuming copper conductors are used and sized for 75°C terminals, what is the minimum standard AWG size required for the feeder conductors to the subpanel, according to NEC 210.19(A)(1) and 215.2(A)(1)?General Electrical Knowledge and Plan Reading
  7. 7.A client's single-phase heating element draws 50A at 240V. If the circuit conductors are sized for this load and the voltage drop is calculated to be 3% of the supply voltage, what is the actual voltage at the heating element?General Electrical Knowledge and Plan Reading
  8. 8.A new outdoor swimming pool is being installed at a residential property. The pool's circulation pump motor is rated for 2 horsepower (hp), 230 volts, single-phase. What is the minimum size, in AWG, of the copper equipment grounding conductor required for this motor circuit, assuming the overcurrent protective device is sized at 125% of the motor FLC?Special Occupancies, Equipment, and Conditions
  9. 9.A newly installed emergency lighting system in a hospital operating room must be supplied by an emergency power source. According to the NEC, what is the maximum time allowed for the emergency power source to supply illumination and power upon failure of the normal supply?Special Occupancies, Equipment, and Conditions
  10. 10.A client requests a new dedicated 120V circuit for a hot tub pump with a nameplate rating of 18A. The circuit will be run through a conduit in the ground for 75 feet. The electrician plans to use copper conductors. What is the minimum required ampacity for the branch circuit conductors, considering NEC requirements for continuous loads?General Electrical Knowledge and Plan Reading
  11. 11.A commercial kitchen is classified as a Class I, Division 1 hazardous location due to the presence of flammable vapors from cooking processes. An explosionproof enclosure is used for electrical equipment. According to NEC Article 500, what is the primary design characteristic of an explosionproof enclosure that makes it suitable for this location?Special Occupancies, Equipment, and Conditions
  12. 12.A technician is troubleshooting a 120V AC circuit that has two loads connected in parallel. Load 1 draws 5A and Load 2 draws 8A. What is the total current drawn from the source?General Electrical Knowledge and Plan Reading
  13. 13.A health care facility is installing a new X-ray machine. The branch circuit supplying the X-ray equipment must be supplied by a minimum of how many separate feeders or branch circuits?Special Occupancies, Equipment, and Conditions
  14. 14.A health care facility requires the installation of a new receptacle in a patient care area where patients are subject to involuntary movement. According to NEC Article 517, what type of receptacle is specifically required for this application?Special Occupancies, Equipment, and Conditions
  15. 15.A technician is performing a diagnostic on a three-phase motor. Using a clamp-on ammeter, the technician measures the phase currents as follows: Phase A = 40A, Phase B = 38A, Phase C = 42A. What does this indicate about the motor's load condition?General Electrical Knowledge and Plan Reading
  16. 16.An electrician is reviewing blueprints for a commercial office building. The legend indicates that a dashed line with three short perpendicular lines (─ ─ ─ ─ ─ ╪ ╪ ╪) represents a specific type of wiring. What does this symbol typically denote in electrical blueprints?General Electrical Knowledge and Plan Reading
  17. 17.A client requires power for a new industrial machine with a nameplate rating of 10 kVA, 3-phase, 480V, and a power factor of 0.8 lagging. What is the approximate real power (kW) drawn by this machine?General Electrical Knowledge and Plan Reading
  18. 18.A client's single-phase AC circuit has an RMS voltage of 120V and a peak current of 17A. Assuming a purely resistive load, what is the approximate RMS current in this circuit?General Electrical Knowledge and Plan Reading
  19. 19.An industrial facility has several large 3-phase motors. A technician observes that Motor A draws 40A, Motor B draws 30A, and Motor C draws 50A on each phase. If these motors are connected to a common 3-phase feeder, what is the approximate total current on one phase of the feeder, assuming balanced loads and no diversity factor applied?General Electrical Knowledge and Plan Reading
  20. 20.A client's industrial facility has a 480V, 3-phase, 3-wire delta electrical service. If a balanced resistive load draws 30A from each line, what is the total apparent power (S) consumed by the load?General Electrical Knowledge and Plan Reading
  21. 21.A circuit has a total resistance of 25 Ω and is connected to a 120 V AC source. What is the total power dissipated by the circuit?General Electrical Knowledge and Plan Reading
  22. 22.A client is installing a new solar photovoltaic (PV) system on a commercial building. The PV array has a maximum system voltage of 500V. What is the minimum size of the equipment grounding conductor (EGC) for a PV circuit with 40A overcurrent protection, using copper conductors?Special Occupancies, Equipment, and Conditions
  23. 23.A client wants to install a new electric oven with a nameplate rating of 12 kW at 240V. According to the National Electrical Code (NEC), what is the minimum standard overcurrent protective device (OCPD) rating required for this appliance if it's considered a non-continuous load?General Electrical Knowledge and Plan Reading
  24. 24.A client has a 3-phase, 4-wire, 208Y/120V electrical service. What is the phase-to-phase voltage between any two of the ungrounded (hot) conductors?General Electrical Knowledge and Plan Reading
  25. 25.A three-phase motor draws 20A per phase at 480V and has a power factor of 0.85. What is the approximate apparent power (S) drawn by the motor?General Electrical Knowledge and Plan Reading
  26. 26.A newly constructed health care facility is installing luminaires in a patient care area where medical personnel interact directly with the patient. What type of branch circuit overcurrent protection is generally required for these luminaires, according to NEC?Special Occupancies, Equipment, and Conditions
  27. 27.A commercial building is being wired, and the electrician is reviewing the electrical blueprints. A specific symbol appears repeatedly, showing a circle with a diagonal line passing through it and an 'S' inside the circle. What does this symbol typically represent?General Electrical Knowledge and Plan Reading
  28. 28.A residential service entrance conductor is being installed for a single-family dwelling with an estimated load of 150A. According to NEC Table 250.66, what is the minimum size aluminum Grounding Electrode Conductor (GEC) required if it is the sole connection to the grounding electrode system?General Electrical Knowledge and Plan Reading
  29. 29.A technician is troubleshooting a series circuit containing three resistors: R1 = 10 Ω, R2 = 15 Ω, and R3 = 25 Ω. If the total voltage applied to the circuit is 100 V, what is the voltage drop across resistor R2?General Electrical Knowledge and Plan Reading
  30. 30.A client is planning a new commercial kitchen. The blueprints indicate a 3-phase, 4-wire, 208Y/120V service. A significant part of the load consists of cooking equipment. What type of load calculation method is generally used for commercial kitchens under the NEC?General Electrical Knowledge and Plan Reading
  31. 31.A technician is installing a new 480Y/277V, 3-phase, 4-wire feeder to supply a lighting panel. The panel has a total non-continuous lighting load of 150A per phase. What is the minimum required ampacity for the feeder overcurrent protective device (OCPD), assuming no demand factors or other loads?General Electrical Knowledge and Plan Reading
  32. 32.A marina service equipment is supplying power to a floating dock. The individual branch circuits for boat slips extend from the service equipment. According to NEC Article 555, what is the maximum permissible voltage for a single-phase branch circuit supplying power to a boat at a floating dock?Special Occupancies, Equipment, and Conditions
  33. 33.A residential service calculation includes a 5.5 kW electric clothes dryer. According to NEC Article 220.54, what is the demand load for this dryer when performing a service calculation for a single-family dwelling?General Electrical Knowledge and Plan Reading
  34. 34.A large concert venue, classified as a place of assembly, requires a permanently installed emergency lighting system. How long must the emergency lighting system be able to maintain illumination upon loss of normal power?Special Occupancies, Equipment, and Conditions
  35. 35.A fire alarm control panel (FACP) is being installed in a new commercial building. The 24V DC fire alarm circuits are routed within the building. What is the minimum required rating for the conductors used for these fire alarm circuits, as specified by NEC Article 760?Special Occupancies, Equipment, and Conditions
  36. 36.A solar photovoltaic (PV) array is installed on a residential rooftop. The array consists of multiple modules connected in series and parallel. What is the minimum required size for the equipment grounding conductor (EGC) for a PV array circuit that has an overcurrent protective device rated at 40 amperes, if the conductors are copper?Special Occupancies, Equipment, and Conditions
  37. 37.A client has a 240V resistive heating element with a current draw of 20A. What is the resistance of the heating element?General Electrical Knowledge and Plan Reading
  38. 38.A technician is troubleshooting a specific type of AC motor that has brushes and a commutator. This motor is known for its high starting torque and speed control capabilities. Which type of motor is the technician likely working on?General Electrical Knowledge and Plan Reading
  39. 39.A commercial building has a 480Y/277V, 3-phase, 4-wire electrical service. A new 3-phase motor rated at 20 HP (Horsepower) is being installed. Assuming the motor's full-load current (FLC) for 480V is 27A (from NEC Table 430.250) and a power factor of 0.85, what is the approximate apparent power (kVA) drawn by this motor?General Electrical Knowledge and Plan Reading
  40. 40.A temporary power installation is set up for a construction site. The temporary feeders and branch circuits are run as open conductors. According to NEC Article 590, what is the minimum clearance required for these open conductors above areas accessible to pedestrians only?Special Occupancies, Equipment, and Conditions
  41. 41.A technician is comparing two conductors, one made of copper and the other of aluminum, both with the same cross-sectional area and length. Which statement accurately describes their electrical resistance?General Electrical Knowledge and Plan Reading
  42. 42.A technician observes that a DC motor runs slower than its rated speed and draws higher than normal current. The power supply voltage is confirmed to be correct. What is the MOST likely electrical issue causing this behavior?General Electrical Knowledge and Plan Reading
  43. 43.A technician is installing a fire alarm control panel (FACP) in a commercial occupancy. The power-limited fire alarm (PLFA) circuit conductors are run in a raceway. What is the minimum permissible separation required between these PLFA circuit conductors and Class 1, nonpower-limited fire alarm (NPLFA), or medium-power network-powered broadband communications circuits in the same raceway, according to NEC?Special Occupancies, Equipment, and Conditions
  44. 44.A client requests a dedicated 20A, 120V circuit for a new medical imaging device. The device manufacturer specifies a maximum voltage drop of 3% at the farthest receptacle, which is 150 feet from the panel. Assuming the circuit uses copper conductors, which AWG conductor size is the minimum required to meet this voltage drop requirement? (Assume a conductor temperature of 75°C and ignore any voltage drop in the service entrance conductors.)General Electrical Knowledge and Plan Reading
  45. 45.An assembly hall with an occupancy of 500 people requires an emergency lighting system. The emergency system is supplied by a generator. According to NEC Article 700, what is the maximum permissible time for the emergency lighting to come on after the normal power supply fails?Special Occupancies, Equipment, and Conditions
  46. 46.A client has a 480V, 3-phase, 3-wire delta system. What is the phase-to-neutral voltage available from this system?General Electrical Knowledge and Plan Reading
  47. 47.A client is installing a new 240V, single-phase motor with a nameplate FLA (Full Load Amperes) of 25A. According to NEC Article 430.22, what is the minimum conductor ampacity required for the motor branch circuit conductors, assuming no other adjustments or corrections?General Electrical Knowledge and Plan Reading
  48. 48.A new service for a multi-family dwelling requires a demand load calculation. The dwelling unit has a 12 kW electric range, a 4 kW electric dryer, and a 10 kW central electric heating system. According to NEC Article 220, what is the demand load for the electric range, after applying the appropriate demand factor?General Electrical Knowledge and Plan Reading
  49. 49.A commercial building utilizes a solar photovoltaic (PV) system with a maximum system voltage of 600V. The PV array is installed on the roof and the DC conductors run in metal conduit through an attic space to an inverter located on the ground floor. What is the minimum required temperature rating for these DC conductors, assuming they are within the scope of NEC Article 690?Special Occupancies, Equipment, and Conditions
  50. 50.A client's single-phase AC motor draws 15 A at 240 V with a power factor of 0.8 lagging. What is the approximate real power (P) consumed by the motor?General Electrical Knowledge and Plan Reading