NEIEP Electrical Fundamentals (360) Practice Test

If an effective voltage is 100 VAC, what is the peak value?

70.7 V 141.4 V 100 V 200 V

Correct Answer:

141.4 V

Explanation:

In a sinusoidal AC waveform, the RMS (effective) voltage is the peak voltage divided by sqrt(2). So the peak value is the RMS voltage times sqrt(2). For 100 V RMS, the peak is 100 × sqrt(2) ≈ 141.4 V. This is the maximum instantaneous voltage of the waveform. 70.7 V would be the RMS value corresponding to a 100 V peak, not the peak for a 100 V RMS. 100 V would imply the peak and RMS are the same, which isn’t true for a sine wave. 200 V would mean the peak is double the RMS, which also doesn’t fit a sine relationship.

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