Subelement A: Principles— Topic 6: Electrical Measurements
Question 3-6A2
Element 3 (GROL)By what factor must the voltage of an AC circuit, as indicated on the scale of an AC voltmeter, be multiplied to obtain the peak voltage value?
Explanation
An AC voltmeter typically measures the Root Mean Square (RMS) voltage of a sinusoidal waveform. RMS voltage is considered the "effective" voltage, equivalent to the DC voltage that would dissipate the same amount of power in a resistive load.
The peak voltage, on the other hand, is the maximum instantaneous voltage reached during a cycle of the AC waveform. For a pure sinusoidal waveform, the relationship between peak voltage (Vp) and RMS voltage (Vrms) is:
Vp = Vrms * $\sqrt{2}$
Since $\sqrt{2}$ is approximately 1.414, to obtain the peak voltage from an RMS reading (what the voltmeter shows), you must multiply the RMS value by 1.414.
Therefore, multiplying the voltmeter reading by 1.414 yields the peak voltage. Option A (0.707) is incorrect because it's the factor used to convert peak voltage *to* RMS voltage (Vrms = Vp * 0.707). Options B and D are not standard conversion factors for sinusoidal AC voltage.
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