Red Seal Electrician Practice
Power factor and three-phaseQuestion 1012 of 1506

Two 120 V sources are 120 degrees apart, like a three-phase supply. What is the voltage between the two hot wires?

  1. 240 V
  2. About 208 V
  3. 120 V
  4. 170 V
Show answer

Correct answer: About 208 V

The phase shift is not 180 degrees, so the voltage is 120 × √3, which is about 208 V.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 7.2: Three-phase Power Systems

Practice power factor and three-phase

Questions last reviewed: 18 October 2026