RMS Voltage

What is RMS Voltage?

The effective value of an AC voltage — the square root of the average of the squared instantaneous voltage over a full cycle — chosen because it delivers the same heating power as a DC voltage of the same numerical value. Household mains ratings like 120V or 230V are always this RMS figure, not the higher instantaneous peak.

The five clues

Engineerdle #47 described RMS Voltage with five clues, revealed one at a time from hardest to most direct. Each clue points at a different property of the concept.

1. 01The number on an AC voltmeter isn't the peak — it's this.
2. 02It's the value that would deliver the same heating power as an equivalent DC source.
3. 03For a sine wave, it's the peak divided by root two.
4. 04Household mains being quoted as 120V or 230V refers to this value, not the peak.
5. 05The square root of the average of the squared instantaneous voltage over one cycle.

More Electrical Engineering concepts

• Norton's TheoremPuzzle #42
• LC Resonant CircuitPuzzle #37
• Skin EffectPuzzle #32
• Electrical InsulatorPuzzle #29
• Photovoltaic EffectPuzzle #26
• InductorPuzzle #22