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Q101EasyAC Fundamentals

Which of the following is a correct representation of peak value in an AC circuit?

Answer & step-by-step solution
Correct answer: D. RMS value*Peak factor
Quick explanation

Peak factor directly relates the maximum (peak) value of an AC waveform to its RMS value. By definition, Peak factor = V_peak / V_rms, so V_peak = Peak factor × V_rms. For a sine wave the peak factor is √2.

Peak factor = Vpeak / Vrms Vpeak = Peak factor × Vrms Vpeak = √2 Vrms

Concept & Reasoning

The RMS value represents the DC-equivalent heating value of an AC quantity, whereas the peak value is the maximum instantaneous magnitude. Peak factor (also called crest factor) is defined as the ratio of peak value to RMS value. Rearranging that definition immediately gives the required representation. Form factor is a different ratio: RMS value divided by average rectified value, so it cannot be used to obtain the peak value directly unless additional waveform information is known.

How to Solve It in the Exam

Remember: peak factor connects PEAK ↔ RMS; form factor connects RMS ↔ average rectified value.

Important Exam Point

Write the definitions of peak factor and form factor before manipulating them; this prevents mixing the two ratios.

Quick Trick

Remember: peak factor connects PEAK ↔ RMS; form factor connects RMS ↔ average rectified value.

Common Mistake

Do not confuse peak factor with form factor. For a sine wave they are approximately 1.414 and 1.11 respectively.

Solution diagram – Which of the following is a correct representation of peak value in an AC…
Exam tipWrite the definitions of peak factor and form factor before manipulating them; this prevents mixing the two ratios.
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