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 valueCorrect
- D. The instantaneous voltage at the moment of measurement
Why C is correct
AC voltmeters and ammeters are calibrated to read RMS values, which represent the effective value equivalent to a DC voltage producing the same heating effect in a resistance. For a 440 V RMS system, the actual peak voltage is approximately 622 V (440 × 1.414).
Cited:NEETS Mod. 2 §1-2