Kiểm tra & Khắc phục sự cốCâu 516 / 521
A homeowner reports that throughout the house, some lights dim while others brighten, and the effect shifts as loads switch on and off. Which service-level fault best explains this?
a.An open (loose or corroded) service neutral
b.A single tripped GFCI receptacle
c.One burned-out light bulb
d.A reversed-polarity outlet in one bedroom
Giải thích
Whole-house dimming/brightening that shifts with load is the classic signature of an open service neutral: the two 120 V legs float in series across 240 V and divide unevenly. A tripped GFCI (b) or a bad bulb (c) affects only one location, and a single reversed outlet (d) does not cause house-wide voltage swings.
Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
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