Question 111: AC fundamentals

Question

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 :

Accepted Answer

$$I = {I_0}\cos (\omega t)$$ say
$$\Rightarrow$$ At maximum $$\omega {t_1} = 0$$ or $${t_1} = 0$$
Then at rms value $$I = {I_0}/\sqrt 2 $$
$$ \Rightarrow \omega {t_2} = \pi /4$$
$$ \Rightarrow \omega ({t_2} - {t_1}) = \pi /4$$
$$\Delta t = {\pi  \over {4\omega }} = {{\pi T} \over {4 	imes 2\pi }}$$
$$ = {1 \over {400}}s$$ or 2.5 ms

Answer

2.5 ms

Answer

1.25 ms

Answer

2.5 s

Answer

0.25 s

AC fundamentals

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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