Free NCCER Commercial Electrician Assessment Practice Questions

Sample Practice Questions

Try these 10 sample questions from the NCCER Commercial Electrician Assessment practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1An electrician must work close enough to an exposed power circuit to contact it with a tool. If the crew chooses OSHA's deenergization method of shock protection, which paired action is required before the work?

   1. A.Deenergize the circuit and ground it.Correct answer: A
   2. B.Deenergize the circuit and tag its controls.
   3. C.Deenergize the circuit and inspect its conductors.
   4. D.Deenergize the circuit and label its disconnect.

   Explanation: OSHA states, "No employer shall permit an employee to work in such proximity to any part of an electric power circuit that the employee could contact the electric power circuit in the course of work, unless the employee is protected against electric shock by deenergizing the circuit and grounding it or by guarding it effectively by insulation or other means." The chosen deenergization route requires both deenergizing and grounding; tagging, inspection, and labeling address different tasks.

   Reference: OSHA 29 CFR 1926.416 — General requirements — 29 CFR 1926.416(a)(1)

2. 2To measure the voltage across a resistive load in a test circuit, how should an electrician connect a voltmeter relative to that load?

   1. A.In parallel with the loadCorrect answer: A
   2. B.In series with the load
   3. C.Across the source and the load in series
   4. D.In place of the load

   Explanation: DOE states, "Voltmeters are connected in parallel with the load (RL) being measured." A parallel connection measures the potential difference across the load.

   Reference: DOE Fundamentals Handbook: Electrical Science, Volume 4 — Test Instruments & Measuring Devices, Voltmeters, p. 5

3. 3An electrician checks the ampacity of a conductor for a commercial branch circuit. Which rating definition matches OSHA's electrical terminology?

   1. A.Continuous current under use conditions without exceeding the temperature rating.Correct answer: A
   2. B.Short-duration current under use conditions without exceeding the temperature rating.
   3. C.Continuous current under use conditions without exceeding the insulation voltage rating.
   4. D.Continuous current under reference conditions without considering temperature rating.

   Explanation: OSHA defines ampacity as "The current in amperes a conductor can carry continuously under the conditions of use without exceeding its temperature rating." Duration, actual use conditions, and temperature limit are all part of this definition.

   Reference: OSHA 29 CFR 1926.449 — Definitions applicable to this subpart — 29 CFR 1926.449, Ampacity

4. 4An electrician sizes a bonding conductor to assure continuity among metal enclosures on a construction project. Under OSHA's bonding rule, which current must that conductor safely carry?

   1. A.The fault current that may be imposed.Correct answer: A
   2. B.The normal continuous load current.
   3. C.The equipment's starting inrush current.
   4. D.The ordinary leakage current to ground.

   Explanation: OSHA states, "If bonding conductors are used to assure electrical continuity, they shall have the capacity to conduct any fault current which may be imposed." The sizing target is prospective fault current, rather than normal load, inrush, or leakage.

   Reference: OSHA 29 CFR 1926.404 — Wiring design and protection — 29 CFR 1926.404(f)(9)

5. 5A commercial cable tray will carry communication-signal cables alongside low-voltage power cables. Under NEMA's cable-installation guidance, what is the highest voltage for which these cables are allowed in the same tray?

   1. A.50 VCorrect answer: A
   2. B.30 V
   3. C.120 V
   4. D.240 V

   Explanation: NEMA states, "Communication signal and power cables with voltage 50 V or less are allowed in the same cable tray." Fifty volts is the published upper limit. Thirty volts is below it, while 120 and 240 exceed it.

   Reference: NEMA BI-50016-2024 Cable Tray Installation Guidelines — Section 4.2(e), p. 42

6. 6A normally open magnetic contactor in a motor starter receives power at its coil. What happens to its armature and main power contacts?

   1. A.The armature pulls in and the main contacts close.Correct answer: A
   2. B.The armature pulls in and the main contacts open.
   3. C.The armature releases and the main contacts close.
   4. D.The armature releases and the main contacts open.

   Explanation: DOE states, "When the coil is energized, the electromagnet attracts the armature and closes the electrical contacts." With this normally open main contact, coil energization pulls in the armature and closes the power circuit.

   Reference: DOE Fundamentals Handbook: Electrical Science, Volume 4 — Electrical Distribution Systems, Motor Controllers, p. 17, Magnetic Controller

7. 7For a new conductor run in a hot, wet industrial area, which three application factors does OSHA expressly require its insulation type to suit?

   1. A.Voltage, operating temperature, and location of use.Correct answer: A
   2. B.Voltage, supply frequency, and location of use.
   3. C.Ampacity, operating temperature, and location of use.
   4. D.Voltage, operating temperature, and circuit length.

   Explanation: OSHA states, "The conductor insulation shall be of a type that is suitable for the voltage, operating temperature, and location of use." Each wrong triple substitutes another real electrical design factor for one of these insulation suitability factors. This judgment is distinct from q-0057, which now tests a wire-table area ratio.

   Reference: OSHA 29 CFR 1926.405 — Wiring Methods and Equipment — 29 CFR 1926.405(f), Conductors for general wiring

8. 8An electrician checks attachment plugs and connectors for a commercial installation. Which pair of ampere ratings does OSHA specifically name in its dead-front construction requirement?

   1. A.15 A and 30 A
   2. B.15 A and 20 ACorrect answer: B
   3. C.20 A and 30 A
   4. D.30 A and 50 A

   Explanation: OSHA states, "All 15- and 20-ampere attachment plugs and connectors shall be constructed so that there are no exposed current-carrying parts except the prongs, blades, or pins." The named ratings are 15 A and 20 A, with dead-front termination covers required by the same paragraph.

   Reference: OSHA 29 CFR 1910.305 — Wiring Methods and Equipment — 29 CFR 1910.305(j)(2)(i)

9. 9A maintenance electrician replaces the component that supplies starting conditions and then limits operating current for a fluorescent lamp. Which lighting component provides both functions?

   1. A.Fluorescent lamp ballastCorrect answer: A
   2. B.Fluorescent lamp starter
   3. C.Lamp circuit capacitor
   4. D.Lamp ignition device

   Explanation: The DOE definition states, "“fluorescent lamp ballast” means a device that is used to start and operate fluorescent lamps by providing a starting voltage and current and limiting the current during normal operation." A ballast provides both stated functions; a starter or ignitor initiates discharge, and a circuit capacitor may adjust power factor, but none is the named ballast.

   Reference: U.S. Department of Energy — Fluorescent Lamp Ballasts — Fluorescent Lamp Ballasts webpage, opening definition paragraph

10. 10A facility electrician reviews fire alarm circuit power classifications under OSHA's electrical special-systems rule. Which pair does the rule use for fire alarm circuits?

    1. A.Power-limited and nonpower-limited circuits.Correct answer: A
    2. B.Initiating-device and notification-appliance circuits.
    3. C.Class A and Class B pathway circuits.
    4. D.Addressable and conventional system circuits.

    Explanation: OSHA states, "Fire alarm circuits shall be classified either as nonpower limited or power limited." The other pairs are real fire-alarm design distinctions, but they are not the electrical power-limitation classification in this paragraph.

    Reference: OSHA 29 CFR 1910.308, Special Systems — 29 CFR 1910.308(d)(1)