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JEE Main 2021 (25 Jul, Shift 2) · AC Basics: Peak, RMS & Average Values

AC Basics: Peak, RMS & Average Values question from JEE Main 2021 (25 Jul, Shift 2)

Q34JEE Main 2021 · 25 JUL · SHIFT 2Medium

AC Basics: Peak, RMS & Average Values

A 10 $\Omega$ resistance is connected across 220V $-$ 50 Hz AC supply. The time taken by the current to change from its maximum value to the rms value is:

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Answer: (a)

Take $I = I_0\cos\omega t$ ; rms value when $\cos\omega t = \frac{1}{\sqrt{2}}$ , i.e. $\omega t = \frac{\pi}{4}$ .
$t = \frac{T}{8}$ with $T = \frac{1}{50}$ s $= 20$ ms
$t = 2.5$ ms (independent of $R$ )
So the answer is (a) 2.5 ms.

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