What a GFCI senses
A GFCI compares the current going out with the current coming back. You put a hand on a broken drill and watch the GFCI shut off when a little goes missing through a person.
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What to try
- 1Pick No ground and set Hand to On the drill. The GFCI sees current missing and shuts off.
- 2Pick No GFCI and try it again. Move Skin from Dry to Wet.
- 3Pick Good ground. The leak runs down the ground pin, and the GFCI still sees it missing. Press Reset to turn it back on.
NEC 2026 sections it covers
- 210.8(A)
- Outdoor receptacles at a home need GFCI protection.
- 210.8
- The GFCI protection it calls for is Class A.
- 406.12(D)(2)
- A GFCI receptacle can replace a two-prong one where there is no ground.
Section numbers only. Read the full text in your code book. Temperatures and times in the visual are teaching models.
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Practice it and teach it
- Protection Map simulationProtect a whole house with GFCI and AFCI devices on a budget, and pass the inspector.
- GFCI and AFCI lessonGFCI and AFCI protection (NEC 2026 210.8, 210.12)
More visuals
- Breaker and wirePlug in loads and watch the wire heat up when the breaker is too big for it.
- What an AFCI sensesA crushed cord arcs. Watch the shape of the current change, and the breaker count it.
- What trips a breakerOn an overload, a strip that bends with heat trips the breaker slowly. On a short or a ground fault, a magnet trips it at once.