PracticeNEC 2023 · 2026 · 330 questions

NEC Practice Quiz: Exam-Style Code Questions

10 exam-style questions per round, drawn from a bank of 330 generated straight from the NEC 2023 tables on this site: ampacity, 240.4(D) breaker limits, conduit fill, box fill, burial depth, grounding conductors, derating and working clearance. Every answer shows the table row it came from.

Per NEC Table 310.16 (not more than three current-carrying conductors, 30°C ambient), what is the allowable ampacity of 14 AWG copper in the 90°C column?

  1. 25A
  2. 30A
  3. 20A
  4. 15A

Answer: 25A. Table 310.16 lists 14 AWG copper at 15A at 60°C, 20A at 75°C, 25A at 90°C.

How this quiz is built and scored

No question here is written by hand. A build script reads each verified NEC data file on WireRef and turns table rows into questions: the correct answer is the cell, the wrong options are neighbouring cells of the same table, and the explanation quotes the row. Each round draws 10 questions spread across the sources below, in random order.

SourceCount
NEC Table 310.16102
NEC 240.4(D)5
NEC Annex C98
NEC Table 314.16(B)7
NEC Table 314.16(A)34
NEC Table 300.5(A)24
NEC Table 250.12218
NEC Table 250.665
NEC Table 310.15(B)(1)(1)22
NEC Table 310.15(C)(1)6
NEC Table 110.26(A)(1)9
Total330

Scoring is one point per question. Your score sets the result tier below. Values are NEC 2023; 9 states now enforce NEC 2026, so check the edition your exam uses on the state pages.

Result tiers

Shop electrician exam prep books on AmazonEvery tier ends here: table lookups are only part of the exam, and a prep book adds timed practice tests and the calculations.

Bring the edition your exam is based on: NEC 2023 code book (paid link), or NEC 2026 (paid link) in the 9 states that enforce it.

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Sample NEC exam questions with answers

Per NEC Table 310.16 (not more than three current-carrying conductors, 30°C ambient), what is the allowable ampacity of 14 AWG copper in the 90°C column?

  1. 25A
  2. 30A
  3. 20A
  4. 15A
Show answer

A. 25A. Table 310.16 lists 14 AWG copper at 15A at 60°C, 20A at 75°C, 25A at 90°C. NEC Table 310.16

Per NEC Table 310.16 (not more than three current-carrying conductors, 30°C ambient), what is the allowable ampacity of 12 AWG copper in the 60°C column?

  1. 20A
  2. 30A
  3. 15A
  4. 25A
Show answer

A. 20A. Table 310.16 lists 12 AWG copper at 20A at 60°C, 25A at 75°C, 30A at 90°C. NEC Table 310.16

Unless a specific exception applies, what is the largest overcurrent device NEC 240.4(D) permits for 12 AWG aluminum?

  1. 30A
  2. 20A
  3. 15A
  4. 25A
Show answer

C. 15A. 240.4(D) limits 12 AWG aluminum to 15A overcurrent protection, even though Table 310.16 lists it at 20A (75°C) and 25A (90°C). The table value is for derating, not for picking the breaker. NEC 240.4(D)

Unless a specific exception applies, what is the largest overcurrent device NEC 240.4(D) permits for 10 AWG aluminum?

  1. 35A
  2. 15A
  3. 30A
  4. 25A
Show answer

D. 25A. 240.4(D) limits 10 AWG aluminum to 25A overcurrent protection, even though Table 310.16 lists it at 30A (75°C) and 35A (90°C). The table value is for derating, not for picking the breaker. NEC 240.4(D)

Per NEC Annex C, how many 14 AWG THHN/THWN-2 conductors are permitted in 1/2 in. EMT?

  1. 22
  2. 12
  3. 11
  4. 9
Show answer

B. 12. Annex C (EMT) allows 12 conductors of 14 AWG THHN/THWN-2 in 1/2 in. EMT. The next size up, 3/4 in., allows 22. Annex C applies only when every conductor is the same size and insulation. NEC Annex C

Per NEC Annex C, how many 12 AWG THHN/THWN-2 conductors are permitted in 1/2 in. EMT?

  1. 5
  2. 16
  3. 9
  4. 12
Show answer

C. 9. Annex C (EMT) allows 9 conductors of 12 AWG THHN/THWN-2 in 1/2 in. EMT. The next size up, 3/4 in., allows 16. Annex C applies only when every conductor is the same size and insulation. NEC Annex C

Per NEC Table 314.16(B), what volume allowance is required for each 18 AWG conductor in a box?

  1. 1.75 cu in.
  2. 2.25 cu in.
  3. 2 cu in.
  4. 1.5 cu in.
Show answer

D. 1.5 cu in.. Table 314.16(B) assigns 1.5 cubic inches to each 18 AWG conductor. NEC Table 314.16(B)

Per NEC Table 314.16(B), what volume allowance is required for each 16 AWG conductor in a box?

  1. 1.75 cu in.
  2. 2 cu in.
  3. 1.5 cu in.
  4. 2.25 cu in.
Show answer

A. 1.75 cu in.. Table 314.16(B) assigns 1.75 cubic inches to each 16 AWG conductor. NEC Table 314.16(B)

Per NEC Table 314.16(A), what is the maximum number of 14 AWG conductors in a 3x2x2 in. device box (10 cu in.)?

  1. 4
  2. 6
  3. 7
  4. 5
Show answer

D. 5. Table 314.16(A) allows 5 conductors of 14 AWG in a 3x2x2 in. device box (10 cu in. at 2 cu in. each), before deducting for devices, clamps and grounds per 314.16(B). NEC Table 314.16(A)

Per NEC Table 314.16(A), what is the maximum number of 12 AWG conductors in a 3x2x2 in. device box (10 cu in.)?

  1. 8
  2. 4
  3. 6
  4. 5
Show answer

B. 4. Table 314.16(A) allows 4 conductors of 12 AWG in a 3x2x2 in. device box (10 cu in. at 2.25 cu in. each), before deducting for devices, clamps and grounds per 314.16(B). NEC Table 314.16(A)

Per NEC Table 300.5(A), what is the minimum cover for direct burial cable in this location: all locations not specified below?

  1. 12 in.
  2. 18 in.
  3. 6 in.
  4. 24 in.
Show answer

D. 24 in.. Table 300.5(A), Direct Burial Cables or Conductors column, "All locations not specified below": 24 in. of cover, measured from the top of the cable or raceway to finished grade. NEC Table 300.5(A)

Per NEC Table 300.5(A), what is the minimum cover for rigid metal conduit (RMC) or IMC in this location: all locations not specified below?

  1. 12 in.
  2. 6 in.
  3. 18 in.
  4. 24 in.
Show answer

B. 6 in.. Table 300.5(A), Rigid Metal Conduit (RMC) or Intermediate Metal Conduit (IMC) column, "All locations not specified below": 6 in. of cover, measured from the top of the cable or raceway to finished grade. NEC Table 300.5(A)

Per NEC Table 250.122, what is the minimum copper equipment grounding conductor for a circuit protected by a 20A overcurrent device?

  1. 8 AWG
  2. 10 AWG
  3. 12 AWG
  4. 14 AWG
Show answer

C. 12 AWG. Table 250.122: OCPD rated not more than 20A takes 12 AWG copper or 10 AWG aluminum. NEC Table 250.122

Per NEC Table 250.122, what is the minimum aluminum equipment grounding conductor for a circuit protected by a 20A overcurrent device?

  1. 10 AWG
  2. 8 AWG
  3. 12 AWG
  4. 6 AWG
Show answer

A. 10 AWG. Table 250.122: OCPD rated not more than 20A takes 12 AWG copper or 10 AWG aluminum. NEC Table 250.122

Per NEC Table 250.66, what is the minimum copper grounding electrode conductor when the largest copper service-entrance conductor is 1 AWG or 1/0 AWG?

  1. 8 AWG
  2. 6 AWG
  3. 2 AWG
  4. 4 AWG
Show answer

B. 6 AWG. Table 250.66: copper service conductors 1 AWG or 1/0 AWG (aluminum 2/0 AWG or 3/0 AWG) take a 6 AWG copper or 4 AWG aluminum GEC. NEC Table 250.66

Per NEC Table 250.66, what is the minimum copper grounding electrode conductor when the largest copper service-entrance conductor is 2/0 AWG or 3/0 AWG?

  1. 8 AWG
  2. 6 AWG
  3. 2 AWG
  4. 4 AWG
Show answer

D. 4 AWG. Table 250.66: copper service conductors 2/0 AWG or 3/0 AWG (aluminum 4/0 AWG or 250 kcmil) take a 4 AWG copper or 2 AWG aluminum GEC. NEC Table 250.66

Per NEC Table 310.15(B)(1)(1), what correction factor applies to a conductor rated 60°C at an ambient of 31-35°C (87-95°F)?

  1. 0.96
  2. 0.94
  3. 0.82
  4. 0.91
Show answer

D. 0.91. Table 310.15(B)(1)(1), 31-35°C row: 0.91 for 60°C, 0.94 for 75°C, 0.96 for 90°C. Multiply the Table 310.16 ampacity by it. NEC Table 310.15(B)(1)(1)

Per NEC Table 310.15(B)(1)(1), what correction factor applies to a conductor rated 75°C at an ambient of 31-35°C (87-95°F)?

  1. 0.96
  2. 0.91
  3. 0.94
  4. 0.88
Show answer

C. 0.94. Table 310.15(B)(1)(1), 31-35°C row: 0.91 for 60°C, 0.94 for 75°C, 0.96 for 90°C. Multiply the Table 310.16 ampacity by it. NEC Table 310.15(B)(1)(1)

Per NEC Table 310.15(C)(1), what adjustment applies with 4-6 current-carrying conductors in a raceway or cable?

  1. 80%
  2. 45%
  3. 70%
  4. 50%
Show answer

A. 80%. Table 310.15(C)(1): 4-6 current-carrying conductors, 80% of the Table 310.16 value. Equipment grounding conductors are not counted. NEC Table 310.15(C)(1)

Per NEC Table 310.15(C)(1), what adjustment applies with 7-9 current-carrying conductors in a raceway or cable?

  1. 80%
  2. 70%
  3. 45%
  4. 50%
Show answer

B. 70%. Table 310.15(C)(1): 7-9 current-carrying conductors, 70% of the Table 310.16 value. Equipment grounding conductors are not counted. NEC Table 310.15(C)(1)

Per NEC Table 110.26(A)(1), what is the minimum depth of working space at equipment 0-150V to ground, Condition 1?

  1. 5 ft
  2. 3.5 ft
  3. 4 ft
  4. 3 ft
Show answer

D. 3 ft. Table 110.26(A)(1), 0-150V: Condition 1 3 ft, Condition 2 3 ft, Condition 3 3 ft. Condition 1: exposed live parts on one side of the working space and no live or grounded parts on the other side, OR exposed live parts on both sides effectively guarded by insulating materials. NEC Table 110.26(A)(1)

Per NEC Table 110.26(A)(1), what is the minimum depth of working space at equipment 0-150V to ground, Condition 2?

  1. 4 ft
  2. 3.5 ft
  3. 3 ft
  4. 5 ft
Show answer

C. 3 ft. Table 110.26(A)(1), 0-150V: Condition 1 3 ft, Condition 2 3 ft, Condition 3 3 ft. Condition 2: exposed live parts on one side and grounded parts on the other side (concrete, brick, or tile walls are considered grounded). NEC Table 110.26(A)(1)

Frequently asked questions

Are these real electrician exam questions?

No. They are exam-style questions generated from the same NEC tables that journeyman and master exams test. Exams also ask calculation and article-navigation questions that table drills do not cover.

How many questions are in the bank?

330, generated from 11 NEC tables and sections. Each round draws 10.

Which NEC edition do the answers use?

NEC 2023. 9 states now enforce NEC 2026; exams follow the edition your state has adopted, so check the state code pages before you study.

Important: For reference only. Not a substitute for a licensed electrician. Electrical work can cause serious injury, death, fire, or property damage if performed incorrectly. Always hire a licensed electrician for electrical work, especially for service upgrades, panel work, and 240V circuits. Values are derived from NFPA 70 (NEC) for educational purposes. Always verify against your locally adopted NEC edition and amendments - local jurisdictions may enforce stricter requirements. WireRef provides reference information only and is not responsible for work performed based on this content. NEC® is a registered trademark of the National Fire Protection Association. Free NEC access via NFPA · OSHA Electrical Safety · Terms of use.

NEC 2023 references verified February 2026

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