USCG Exam PracticeElectrical measuring devices and instrumentation
An AC voltmeter connected to a 440 V shipboard distribution bus displays 440 V. What value does this reading represent?
- A. The peak voltage of the sine wave
- B. The average value of one half-cycle
- ✓ The root-mean-square (RMS) effective voltageCorrect
- D. The instantaneous voltage at the moment of measurement
Why C is correct
AC voltmeters and ammeters read RMS values by design. For a 440 V system, RMS = 0.707 × peak, meaning the actual peak voltage is approximately 622 V. Equipment nameplates and meter scales are stated in RMS.
Cited:NEETS Mod. 2 §1-2