Free NCCER Industrial Electrician Knowledge Assessment Practice Questions

Sample Practice Questions

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

1. 1While preparing to service an industrial motor, an electrician must isolate its electrical energy. Which device is an energy-isolating device under OSHA's lockout rule?

   1. A. A selector switch
   2. B. A disconnect switch
   3. C. A start push button
   4. D. A control-circuit interlock

   Answer: B

   Explanation: The definition includes "a disconnect switch" and excludes push buttons, selector switches, and other control-circuit devices. The disconnect switch physically isolates the motor supply.

   Reference: OSHA 29 CFR 1910.147: Control of Hazardous Energy — 1910.147(b), Energy isolating device

2. 2An electrician selects a fitting and support for a 3/4-trade-size EMT run. What trade size must those components be marked for under Steel Tube Institute guidance?

   1. A. Trade size 1/2
   2. B. Trade size 3/4
   3. C. Trade size 1
   4. D. Trade size 1 1/2

   Answer: B

   Explanation: The Institute says, "Fittings and raceway support shall be used only with conduit of the trade size indicated on the fitting or raceway support or its smallest unit shipping container." For this 3/4 EMT run, both selected components must be intended for trade size 3/4.

   Reference: Steel Tube Institute: Fittings for Use with RMC, IMC and EMT — Fittings for Use with RMC, IMC and EMT, Size and raceway type

3. 3A DC control load lies between test points TP2 and TP3. TP1 is at the supply positive terminal ahead of the feeder; TP4 is at the supply return behind the feeder. Feeder voltage drop is nonzero. Which probe pair measures voltage directly across the load?

   1. A. TP1 and TP4
   2. B. TP1 and TP2
   3. C. TP2 and TP3
   4. D. TP3 and TP4

   Answer: C

   Explanation: DOE states, "Voltmeters are connected in parallel with the load (RL) being measured." TP2 and TP3 are the two load terminals. TP1–TP4 spans the source, whereas TP1–TP2 and TP3–TP4 span feeder segments.

   Reference: DOE Fundamentals Handbook: Electrical Science, Volume 4 — ES-14, page 5, Voltmeters

4. 4An electrician plans a steel conduit run with closed raceway between two pull points. Under the maximum stated by the Steel Tube Institute for the National Electrical Code, what is the greatest total change of direction allowed in that span?

   1. A. 180 degrees
   2. B. 270 degrees
   3. C. 360 degrees
   4. D. 450 degrees

   Answer: C

   Explanation: The Steel Tube Institute states, "the National Electric Code® allows up to 360 degrees between pulling points." The question asks for the upper limit, so a 450-degree total exceeds it and the smaller totals are not the stated maximum.

   Reference: Steel Tube Institute: Bending — Bending, General Information

5. 5At an industrial establishment with qualified-person maintenance and supervision, an electrician plans listed single-conductor cable in a ladder cable tray. What is the smallest permitted cable size?

   1. A. No. 2 AWG
   2. B. No. 1 AWG
   3. C. No. 1/0 AWG
   4. D. No. 2/0 AWG

   Answer: C

   Explanation: OSHA states, "Single conductor cable; the cable shall be No. 1/0 or larger and shall be of a type listed and marked on the surface for use in cable trays." No. 1/0 AWG is the smallest size allowed under these specified industrial conditions.

   Reference: OSHA 29 CFR 1910.305: Wiring methods, components, and equipment for general use — 29 CFR 1910.305(a)(3)(ii) and (ii)(A)

6. 6A three-wire DC system supplies premises wiring in an industrial facility. Which conductor does OSHA require to be grounded?

   1. A. The neutral conductor
   2. B. The positive conductor
   3. C. The negative conductor
   4. D. The equipment conductor

   Answer: A

   Explanation: OSHA states, "All 3-wire dc systems shall have their neutral conductor grounded." The conductor serving as the neutral is the required grounded conductor for the stated system.

   Reference: OSHA 29 CFR 1910.304: Wiring design and protection — 29 CFR 1910.304(g)(1)(i)

7. 7A feeder protective device will interrupt the grounded circuit conductor during an overcurrent event, outside the motor-running-overload exception. How must its contacts open the circuit conductors to comply with OSHA?

   1. A. All circuit conductors simultaneously
   2. B. Grounded conductor before ungrounded conductors
   3. C. Ungrounded conductors before grounded conductor
   4. D. Each conductor in a separate switching interval

   Answer: A

   Explanation: OSHA says an overcurrent device may interrupt the grounded conductor only if "all conductors of the circuit are opened simultaneously." Grounded-first, ungrounded-first, and staggered opening sequences do not meet that simultaneous condition.

   Reference: OSHA 29 CFR 1910.304: Wiring design and protection — 29 CFR 1910.304(f)(1)(ii)

8. 8An electrician is checking the expected field speed of a 60 Hz, four-pole AC motor. What synchronous speed should be used?

   1. A. 900 rpm
   2. B. 1,200 rpm
   3. C. 1,800 rpm
   4. D. 3,600 rpm

   Answer: C

   Explanation: The DOE handbook says synchronous speed "can be found by using Equation (12-2)." The displayed equation on ES-12 page 5 is 120f/P, with P defined as the total number of poles. A 60-Hz four-pole field therefore turns at 120 × 60 / 4 = 1,800 rpm.

   Reference: DOE Fundamentals Handbook: Electrical Science, Volume 4 — AC Motor Theory, Eq. 12-2, page 5

9. 9An industrial control circuit needs a transformer with a relatively low volt-ampere rating to supply a stable control voltage. Which type is described by that function?

   1. A. A distribution transformer
   2. B. A control transformer
   3. C. An instrument current transformer
   4. D. An instrument potential transformer

   Answer: B

   Explanation: DOE states: "Control transformers are generally used in electronic circuits that require constant voltage or constant current with a low power or volt-amp rating." The alternatives serve distribution or instrument-measurement functions instead.

   Reference: DOE Fundamentals Handbook: Electrical Science, Volume 4 — Transformers, Transformer Types, Control Transformer, page 18

10. 10During medium-voltage cable termination, an electrician identifies several cable layers. At the termination of which layer does OSHA expressly require stress-reduction means?

    1. A. Factory-applied shielding
    2. B. Metal cable sheath
    3. C. Outer cable jacket
    4. D. Current-carrying conductor

    Answer: A

    Explanation: OSHA says, "Stress reduction means shall be provided at all terminations of factory-applied shielding." The sheath, jacket, and conductor have other termination needs, but this provision locates electrical stress reduction at the shield termination.

    Reference: OSHA 29 CFR 1910.308: Special systems — 29 CFR 1910.308(a)(3)(i), Insulation shielding