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NEC Code Knowledge Practice Test (2023 NEC)

Finding your way around the National Electrical Code and the long-standing requirements electrician exams ask about. Questions cite the section; you need your own code book.

213 questions · 5 topics · free, no sign-up

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Mixed practice test

10 questions, graded as you go, with the reason for every answer. No sign-up.

Timed mock exam

50 questions in 60 minutes, drawn from every topic. No answers shown until the end, then a score, your weakest topics and a review of what you missed.

Practise by topic

Sample questions

In which conductor must the switching for three-way and four-way switches be done?

  1. Only in the grounded conductor
  2. In both of the circuit conductors
  3. In the equipment grounding conductor
  4. Only in the ungrounded conductor
Show the answer

D. Only in the ungrounded conductor

Three-way and four-way switches are wired so all switching is in the ungrounded conductor. Switching the grounded conductor would leave the load energized with respect to ground when it is off.

Reference: NEC 2023, 404.2(A)

A 120/240 V panelboard is 20 in. wide. What is the minimum width of the working space in front of it?

  1. 20 in.
  2. 24 in.
  3. 30 in.
  4. 36 in.
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C. 30 in.

The working space must be as wide as the equipment or 30 in., whichever is greater. Matching the 20 in. width of the panel is the common mistake.

Reference: NEC 2023, 110.26(A)(2)

How do Chapters 5, 6 and 7 relate to the general rules found in the earlier chapters?

  1. They apply only where Chapter 8 refers to them
  2. They are informational and cannot be enforced
  3. They replace Chapters 1 to 4 for all occupancies
  4. They may supplement or modify the general rules
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D. They may supplement or modify the general rules

Chapters 5, 6 and 7 cover special occupancies, special equipment and special conditions, and they can add to or change the general rules for those cases. They do not throw out the general chapters; the general rules still apply except where the special chapter changes them.

Reference: NEC 2023, 90.3

Where must the service disconnecting means be installed?

  1. At a readily accessible spot nearest the conductor entry
  2. At any point inside, if the conductors are in conduit
  3. At the most central location within the building
  4. At the panelboard that serves the largest load
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A. At a readily accessible spot nearest the conductor entry

The service disconnect goes in a readily accessible location outside the building or inside nearest the point where the service conductors enter. Service conductors have no overcurrent protection at their supply end, so their length inside the building is kept short.

Reference: NEC 2023, 230.70(A)(1)

How must the conductors of one circuit, including the grounded and equipment grounding conductors, be routed?

  1. In separate raceways for each of the phases
  2. With the neutral run in its own raceway
  3. By any route that ends at the same box
  4. Together in the same raceway, cable or trench
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D. Together in the same raceway, cable or trench

All conductors of a circuit are kept together in the same raceway, cable, trench or cord. Keeping them together cancels magnetic fields and keeps the fault path impedance low.

Reference: NEC 2023, 300.3(B)

Exams this helps with

ExamWho runs itWhere
Journeyman electrician readyState boards (PSI, Prov, ICC, Pearson VUE)United States (varies by state)
Master electrician readyState boardsUnited States (varies by state)
Residential wireman / residential electrician readyState boardsUnited States (varies by state)

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