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JEE Main 2022 (24 Jun, Shift 1) · AC Basics: Peak, RMS & Average Values

AC Basics: Peak, RMS & Average Values question from JEE Main 2022 (24 Jun, Shift 1)

Q27JEE Main 2022 · 24 JUN · SHIFT 1Medium

AC Basics: Peak, RMS & Average Values

A resistance of 40 $\Omega$ is connected to a source of alternating current rated 220 V, 50 Hz. Find the time taken by the current to change from its maximum value to the rms value:

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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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