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 voltage over one full cycle
- ✓ The RMS (effective) voltageCorrect
- D. The instantaneous voltage at the moment of measurement
Why C is correct
AC voltmeters are calibrated to read RMS values. For a 440 V system, the RMS value is 440 V, while the actual peak voltage is approximately 622 V (440 × 1.414). The full-cycle average of a sine wave is zero, and instantaneous values vary continuously.
Cited:NEETS Mod. 2 §1-2