Mạch nhánh & Đi dâyCâu 198 / 521
The internal area of 3/4" EMT is 0.533 in² per Table 4. What is the 40% usable fill area for three or more conductors?
a.0.165 in²
b.0.213 in²
c.0.283 in²
d.0.122 in²
Giải thích
0.533 × 0.40 = 0.213 in². The 31% area is 0.165 in² and the 53% area is 0.283 in²; 0.122 in² is the 40% area of the smaller 1/2" EMT.
Trích dẫn luật: 2023 NEC Chapter 9, Table 4Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- Per Annex C, Table C.1, what is the maximum number of 12 AWG THHN conductors permitted in 3/4" EMT?
- Per Annex C, Table C.1, what is the maximum number of 10 AWG THHN conductors permitted in 1/2" EMT?
- The internal cross-sectional area of 1/2" EMT is 0.304 in³ per Table 4. For three or more conductors, what usable fill area (40%) is available?
- Given a 40% usable fill area of 0.213 in² (3/4" EMT) and a 12 AWG THHN cross-sectional area of 0.0133 in² (Table 5), how many 12 AWG THHN conductors fit?
- Six current-carrying 12 AWG THHN conductors (90°C, 30 A base) share a raceway. Applying only the adjustment factor for 4–6 conductors, what is the adjusted ampacity?
- Per Table 310.15(C)(1), what adjustment (derating) factor applies when there are 7 to 9 current-carrying conductors in a raceway?
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