FCC Exam Question: 6A530

By what factor must the voltage of an AC circuit, as indicated on the scale of an AC voltmeter, bemultiplied to obtain the peak value?

A. 141
B. The multiplying factor is
C. The multiplying factor is
D. The multiplying factor is
Correct Answer: B

Explanation: AC voltmeters typically display the Root Mean Square (RMS) value of a sinusoidal waveform. The RMS value represents the effective voltage, meaning it would produce the same heating effect in a resistive load as an equivalent DC voltage. For a pure sine wave, the relationship between the peak voltage ($V_p$) and the RMS voltage ($V_{RMS}$) is given by: $V_p = V_{RMS} \times \sqrt{2}$ Therefore, to convert the RMS reading shown on an AC voltmeter to its peak value, you must multiply the reading by $\sqrt{2}$. The value of $\sqrt{2}$ is approximately 1.414. Options A, C, and D are incorrect. Option C ($1/\sqrt{2}$) would convert peak voltage to RMS voltage. Options A (141) and D (2) are incorrect factors for this conversion.

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Includes Elements 1, 3, 6, 7R, 8, and 9.