FCC Exam Question: 3-6A3

What is the RMS voltage at a common household electrical power outlet?

A. 331-V AC.
B. 82.7-V AC.
C. 165.5-V AC.
D. 117-V AC.
Correct Answer: D

Explanation: Household electrical power outlets in North America typically supply alternating current (AC) with a nominal RMS voltage of around 110V to 125V. The RMS (Root Mean Square) voltage is the effective value of the AC waveform, equivalent to the DC voltage that would produce the same amount of power in a resistive load. Therefore, 117-V AC is a common and correct specification for the RMS voltage at a standard outlet. Option C, 165.5-V AC, is approximately the *peak* voltage for a 117-V RMS AC supply (117V multiplied by the square root of 2, which is about 1.414). It is not the RMS voltage itself. Options A and B are not typical RMS voltages found at common household outlets. Knowing the RMS voltage is crucial for safely connecting and powering amateur radio equipment.

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