Red Seal Electrician Practice
Power factor and three-phaseQuestion 1010 of 1506

The two hot wires of a split-phase system are 120 V each against the neutral. How is the voltage between the hot wires found?

  1. Subtract one source from the other, which gives 240 V
  2. Add the two as plain numbers, which gives 120 V
  3. Multiply one by the square root of 3, which gives 208 V
  4. Divide by two, which gives 60 V
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Correct answer: Subtract one source from the other, which gives 240 V

The sources are opposed relative to the neutral, so subtracting 120 ∠180 degrees from 120 ∠0 degrees gives 240 V.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 7.1: Single-Phase Power Systems

Practice power factor and three-phase

Questions last reviewed: 18 October 2026