Theory & SafetyCâu 114 / 120
A single-phase transformer has a 480-volt primary and a 120-volt secondary. If the secondary carries 100 amperes, what is the approximate primary current?
a.50 amperes
b.100 amperes
c.400 amperes
d.25 amperes
Giải thích
Voltage and current transform inversely, so the 4 to 1 voltage ratio produces a 1 to 4 current ratio: 100 / 4 = 25 amperes on the primary. Neglecting losses, the volt-amperes match on both sides, 480 x 25 = 120 x 100 = 12,000 VA. The 400-ampere answer inverts the ratio and would represent an impossible power gain.
Luyện miễn phí toàn bộ 120 câu hỏi — không cần đăng ký.
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