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RMS value is defined based on which of the following?

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Answer & Explanation

Correct AnswerA. Heating effect

Quick Explanation

RMS value is defined as the DC value that would produce the same heating effect in a given resistance over the same time. That is why RMS—not average or peak—is used for AC equipment voltage/current ratings.

Formula / Key Relation

I_rms = √[(1/T)∫₀ᵀ i²(t)dt]

For sine:

I_rms = I_m/√2

P_R = I_rms²R

Detailed Explanation

Concept & Reasoning

Joule heating is proportional to i²R, so alternating current must be squared before averaging. Taking the square root of the mean square gives an effective value directly comparable with DC for resistive power. For a sine wave, I_rms=I_m/√2.

How to Solve It in the Exam

RMS = equivalent heating effect.

Important Exam Point

Square → mean → root is both the name and the calculation.

Related Revision Path

This question sits in the revision path Basic Electrical Engineering → AC Fundamentals → RMS Value .

Heating-Effect Definition of RMS explanatory diagram

Quick Trick

RMS = equivalent heating effect.

Common Mistake

Using average AC current, which is zero over a complete symmetrical cycle.

Exam Tip

Square → mean → root is both the name and the calculation.

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