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

Option 1 -

2.5 ms

Option 2 -

1.25 ms

Option 3 -

2.5 s

Option 4 -

0.25 s

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1 Answer

Answered by

Vishal Baghel | Contributor-Level 10

3 months ago

Correct Option - 1

Detailed Solution:

Let l = l₀ cos wt

l = l₀, at t₁ = 0

& $l = \frac{l_{0}}{\sqrt[]{2}}, a t ω t = \frac{π}{4} \Rightarrow t_{2} = \frac{π}{4 ω}$

$t_{2} = \frac{π}{4 ω} = \frac{π}{4} \times \frac{T}{2 π} = \frac{T}{8}$

$t_{2} = \frac{1}{8} \times \frac{1}{υ} (T = \frac{1}{υ})$

$t_{2} = \frac{1}{8 \times 50}$

^{$t_{2} = \frac{1}{4 \times 1 0^{+ 2}}$}

= 0.25 × 10^-2

t₂ = 2.5 ms

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