Subelement A: Principles— Topic 6: Electrical Measurements
Question 3-6A6
Element 3 (GROL)What is the peak voltage at a common household electrical outlet?
Explanation
Household electrical outlets provide alternating current (AC), typically rated at 117 or 120 volts RMS (Root Mean Square). RMS voltage is the effective DC equivalent voltage for power delivery and is what voltmeters usually measure. For a sinusoidal AC waveform, the peak voltage is found by multiplying the RMS voltage by the square root of 2 (approximately 1.414).
Using 117 volts RMS, which is common in exam questions:
Peak Voltage = 117V RMS * sqrt(2) ≈ 117V * 1.414 ≈ 165.44 volts.
Therefore, **165.5 volts** is the closest and correct peak voltage.
Option B (117 volts) is the RMS value itself, not the peak. Option A (234 volts) is approximately double the RMS voltage, sometimes seen in 240V split-phase connections, but not the peak of a single phase. Option C (331 volts) would be the peak voltage for an AC circuit with approximately 234V RMS.
Related Questions
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