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NEC Code Questions Practice Test-10

Free online Practice Test on NEC Code Questions-10

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This NEC Code Questions Practice Test-10 has 10 questions with detailed answers and NEC references. Take the full test, review every wrong answer, and look up the NEC article it references before moving on.

Tip: Mixed-format test — questions jump between topics just like the real exam. Don't spend more than 90 seconds on any one question.

Topics covered: All NEC chapters — branch circuits, grounding, conductors, wiring methods, motors, and more.
Passing score: Aim for 80%+ consistently before scheduling your exam.
Questions: 10 multiple-choice, one correct answer each

10

Questions

15 min

Time

70%

Pass

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NEC Code Questions Practice Test-10 — Question List

Question 1: What is the required size of a neutral conductor for a dwelling unit with a calculated load of 220 A. The unbalanced load is 120 A and service disconnect rating is 250A.

1 AWG
2 AWG
3 AWG
4 AWG

NEC Reference: NEC 310.15(B)(16)

Question 2: If a service is fed by three parallel sets of 400 kcmil conductors, what is the required conductor size for GEC?

3/0 AWG
2/0 AWG
2 AWG
4 AWG

NEC Reference: NEC 250.166

Question 3: A 400 breaker protects a set of 450 kcmil feeder conductors. A feeder fed from 450 kcmil feeder that supply disconnects with 25 A over current device. What is the minimum size conductor for these tap?

8 AWG
6 AWG
4 AWG
16 AWG

NEC Reference: NEC 310.15(B)(16)

Question 4: What size service entrance conductors are required for 250 A continuous three phase load if the terminals are at ambient temperature of 70 C?

3/0 AWG
250 kcmil
400 kcmil
2/0 AWG

NEC Reference: NEC 312.5

Question 5: Under which of the following condition the on-site generator is not considered as separately derived system?

When the generator does not have neutral conductor
When the generator is placed near the feeder service conductor panel board
Generator having transfer witch that switches the neutral conductor also
When generator neutral conductor is solidly interconnected service supply system neutral conductor

NEC Reference: NEC 250.30

Question 6: When the circuits are protected by a over current device rating of 1000 A, what size bonding jumper is required for each metal raceway?

1/0 AWG
2/0 AWG
3/0 AWG
4 AWG

NEC Reference: NEC 250.122

Question 7: When five conductors each with an ampacity of 25 A bundled through NM cable, what is the adjusted ampacity of each cable.

25 amperes
20 amperes
30 amperes
22.5 amperes

NEC Reference: NEC 310.15(B)(3)(a)

Question 8: A 40 KVA , 480 V three phase transformer has a primary over current protection device is rated at 75 A. What is the size of primary conductor that can be used?

2 AWG
4 AWG
3 AWG
1 AWG

NEC Reference: NEC 310.15(B)(16)

Question 9: How many number of 500 kcmil THWN conductors that can be installed in a 4 in. * 4 in. wireway?

4 conductors
5 conductors
6 conductors
7 conductors

NEC Reference: NEC 376.22(A)

Question 10: What size service entrance conductors are required for 250 A continuous three phase load if the terminals are at ambient temperature of 70 C?

3/0 AWG
250 kcmil
400 kcmil
2/0 AWG

NEC Reference: NEC 312.5

EXAM CARD NEC_PRACTICE

Questions10

Time limit15 min

Pass score70%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

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Source: NEC 2026 (NFPA 70)