An AC source rated 220V , 50Hz is connected to a resistor.


An AC source rated $220 \mathrm{~V}, 50 \mathrm{~Hz}$ is connected to a resistor. The time taken by the current to change from its maximum to the rms value is :

  1. $2.5 \mathrm{~ms}$

  2. $25 \mathrm{~ms}$

  3.  $2.5 \mathrm{~s}$

  4. $0.25 \mathrm{~ms}$

Correct Option: 1


$\mathrm{i}=\mathrm{i}_{0} \cos (\omega \mathrm{t})$

$\mathrm{i}=\mathrm{i}_{0}$ at $\mathrm{8}=0$

$\mathrm{i}=\frac{\mathrm{i}_{0}}{\sqrt{2}}$ at $\omega \mathrm{t}=\frac{\pi}{4}$

$\mathrm{t}=\frac{\pi}{4 \omega}=\frac{\pi}{4(2 \pi \mathrm{f})}=\frac{1}{8 \mathrm{f}}$

$\mathrm{t}=\frac{1}{400}=2.5 \mathrm{~ms}$

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