Whether analog or digital, what are most AC...

🔍 Key Concepts

• The difference between instantaneous, average, peak, and RMS (root-mean-square) values of an AC sine wave • How most AC meters are designed and what quantity best represents equivalent heating power compared to DC • Which quantity is most useful for sizing electrical equipment and conductors

💭 Think About

• For a pure sine wave, which value (peak, peak-to-peak, average, or RMS) best represents the SAME heating effect as a DC voltage? • When you see a household AC rating like "120 V AC" in North America, is that a peak, average, peak-to-peak, or RMS value? • If a meter is intended for practical power and safety calculations, which of these four quantities would be the most useful to display directly?

✅ Before You Answer

• Be clear on the definition of RMS voltage and why it matters for power/heat in resistive loads • Recall what value is marked on utility mains voltage and most AC nameplates (e.g., 120 V, 230 V) • Eliminate options that represent instantaneous extremes of the waveform rather than its effective working value

Whether analog or digital, what are most AC voltmeters calibrated to measure?

peak-to-peak voltage

average voltage

peak voltage only

root-mean-square voltage

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