Electrical Engineering - RC Circuits - Discussion

Discussion Forum : RC Circuits - General Questions (Q.No. 9)
9.
When the frequency of the source voltage decreases, the impedance of a parallel RC circuit
increases
decreases
does not change
decreases to zero
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
8 comments Page 1 of 1.

Mohsin Khalid said:   7 years ago
Z = 1/√(1/R)^2+(WC)^2.

WC = 2πfC.

As f dec, the term (WC)^2 dec and as a result, overall denominator decreases, ultimately Z increases.

Vipin said:   7 years ago
Thank you @Rams.

Aamir said:   7 years ago
The correct answer must be B.

Gulappa said:   8 years ago
Yes, agree @Raven.

Raven zero said:   9 years ago
In parallel circuit 1/Z = 1/R + 1/Xc.

Since, Xc = 1/(2 * f * C) which is Xc is inversely proportional f.

Thus in the parallel circuit the higher the resistance the lower the total resistance(impedance)
therefore if the frequency decrease, the impedance will be decreased. How come it will be increased?
(1)

Saurabh kumar said:   1 decade ago
We know that w = 2*pi*f.

So Xc = 1/2*pi*f*c.

& V^ = r^+xc^, Reactance inversely proportional to frequency.

Also, v = 1/2*pi*f, from this equation clearly we have seen that we is inversely proportion to the frequency but in this question we is decrease. so f is increase.

Rams said:   1 decade ago
In parallel circuits, Z = R+Xc.
Here Xc = 1/(2*pi*f*c).

Reactance inversely proportional to frequency.
As given in the problem supply frequency decreases means Xc is increases.

So obviously Z increases.

Fahad said:   1 decade ago
Impedance (reactance) has inverse relation with frequency for a capacitor (constant capacitance).

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