What a watt is
Watts are volts times amps. They tell you how fast a load uses energy. You run a bulb, a heater, and a water heater and watch the clock count the watt-hours your power bill is based on.
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What to try
- 1Start on Heater at 120 V. It draws 12.5 amps and uses 1,500 watts. Then set Load to Bulb and compare.
- 2Set Load to Heater and Volts to 240 V. The 240 volt heater makes the same 1,500 watts on half the amps.
- 3Press Play, then Faster. Energy used keeps climbing while the watts stay the same, because watts are a rate.
NEC 2026 sections it covers
- 120.5(A)
- 120 V and 240 V are nominal system voltages.
- 424.5
- A baseboard heater counts as a continuous load.
- 422.13
- A water heater counts as a continuous load.
- 210.20(A)
- A continuous load gets a breaker of at least 125% of its amps.
- 240.4(D)
- 12 and 10 AWG copper get 20 and 30 A breakers at most.
- 200.8(C)(1)
- A white wire used as a hot is re-marked with tape at both ends.
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.