Practice test

Electrician Practice Exam 12

Advanced electrician practice exam on conductor ampacity derating, feeder sizing, motor circuits, and grounding under the NEC. 25 timed questions explained.

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These questions are for study practice only and are not official exam questions.

Question 1

1

A 480Y/277 V feeder supplies a 100 A continuous lighting load and a 60 A noncontinuous load. What minimum feeder conductor ampacity is required before derating?

Question 2

2

Four THHN conductors share a raceway in a 40 C ambient. An 8 AWG copper has a 90 C ampacity of 55 A. After the 40 C correction (0.91) and the 80% adjustment for 4 conductors, the adjusted ampacity is about:

Question 3

3

A 400 A service has parallel 250 kcmil copper per phase. Per NEC Table 250.66, what minimum copper grounding electrode conductor is required?

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