Branch Circuits & WiringQuestion 229 of 521
A 120 V single-phase circuit uses 12 AWG copper (6,530 cmil) carrying 20 A over a one-way length of 100 ft. Using VD = 2 × K × I × L ÷ cmil with K = 12.9, what is the approximate voltage drop?
a.7.9 V (about 6.6%)
b.3.9 V (about 3.3%)
c.2.0 V (about 1.7%)
d.5.0 V (about 4.2%)
Explanation
VD = 2 × 12.9 × 20 × 100 ÷ 6,530 = 51,600 ÷ 6,530 ≈ 7.9 V, which is 7.9/120 ≈ 6.6%. The lower values would require either a shorter run or a larger conductor.
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