Parallel circuit
Receptacles on one circuit give each load its own path from the black wire to the white. You switch loads on and off and watch their amps add up on the wire from the breaker.
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What to try
- 1Start with the lamp and the space heater on. The feed wire carries 13.0 amps. That is 0.5 for the lamp plus 12.5 for the heater.
- 2Set Space heater to Off. The lamp still gets 120 volts, because it has its own path.
- 3Turn the space heater back on and set Iron to On. The feed wire now carries 23.0 amps, more than the 20 amp breaker is made for.
NEC 2026 sections it covers
- 240.4(D)
- 12 AWG copper gets a 20 A breaker at most.
- Table 210.21(B)(3)
- A 20 A circuit with several receptacles may use 20 A receptacles.
- 210.12(B)
- Bedroom circuits in a home also need AFCI protection.
Section numbers only. Read the full text in your code book. Temperatures and times in the visual are teaching models.
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More visuals
- A circuit is a loopCurrent flows only when it has a full path out and back. Open the switch or break a wire and watch it stop.
- Conductors and insulatorsPut copper, aluminum, rubber, or skin on the meter and see how hard each one makes it for current to get through.
- Volts, amps, and ohmsChange the voltage or the heater and watch the amps follow. Amps equal volts divided by ohms.