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Electrical mathQuestion 1178 of 1506

A scope shows a sine wave with a peak of 339 V. What is the RMS value?

  1. 339 V
  2. 240 V
  3. 216 V
  4. 480 V
Show answer

Correct answer: 240 V

RMS = 0.707 x peak = 0.707 x 339 V = about 240 V. The 216 V choice uses the average factor of 0.637.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 12.1: AC Voltmeters and Ammeters

Practice electrical math

Questions last reviewed: 18 October 2026