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SESK: Stuff Everyone Should Know · sesk.info/ham-black-wire-hot

In a US three-wire 120 V AC cable, what does black wire insulation mean?

Hot.

  1. Neutral
  2. Equipment ground
  3. Hot ✔

Why: In US household wiring, black is the hot wire, white is neutral, and green or bare is ground. Treat black as live and dangerous.

Huh, didn't know that: Fuses and breakers in 120 V circuits go in series with the hot wire only.

The dad joke
Why did the black wire get all the attention? It was the hottest one there.
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Sources

  1. NCVEC 2026-2030 Technician Question Pool (Element 2), errata Feb 19, 2026 https://www.ncvec.org/downloads/2026-2030%20Technician%20Pool%20and%20Syllabus%20Public%20Release%20Feb%2019%202026.pdf

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