Electrical Engineering - RLC Circuits and Resonance - Discussion

Discussion Forum : RLC Circuits and Resonance - General Questions (Q.No. 11)
11.
If the resistance in parallel with a parallel resonant circuit is reduced, the bandwidth
disappears
becomes sharper
increases
decreases
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
16 comments Page 1 of 2.

Vasiq said:   1 decade ago
I don't think this is right. According to wikipedia, the Q factor of a parallel RLC circuit is: R*sqrt(C/L). This implies that decreasing the resistance would decrease the Q factor. And since, Q factor and bandwidth are inversely proportional, the bandwidth would increase!

Gopal said:   1 decade ago
I am also having same perception with @Vasiq, also Q factor is the ratio of resistance to inductive reactance. If resistance increases then Q factor also increase & consequently Band width decreases as both inversely proportional to each other.

Shashikant said:   6 years ago
In parallel RLC circuit q=r""L/c.

So when r decreases q decreases.and b.w= resonant frequency/q factor.
So if q decreases then bandwidth must increase. Make high r-value get power loss to have high q in the circuit.
(1)

Jeya said:   1 decade ago
Bandwidth = fr/Q --- eqn1.

fr = resonance frequency, Q=Quality factor.
fr = 1/2*pi*sqrt(LC).
Q = 1/(R*sqrt(LC).

If R decreases, Q increases from eqn1 Q increases, bandwidth decreases.

Ashwini said:   6 years ago
BW=fr/Q.
Q=2πfrL/R.

BW=frR/2πfrL.
=R/2πL.

So Resistance is proportional to Bandwidth.

As Resistance decreases Bandwidth also decreases.

Gangadhar said:   7 years ago
Here;

Q = (XL/R)
BW = Fr/Q there fore
BW = (Fr*R) / XL

From the above equation, it is clear the BW is directly proportional to Resistor(R).

Gopal Gupta said:   5 years ago
@All.

For those who are saying Q=XL/R. I want to correct them. This Q is for series RLC ckt. Given question is about parallel. So here Q=XC*R.

Shashi kant said:   9 years ago
We know for parallel resonance circuit Q = wRC or = R/wL. So R increases Q increases.

B.W = f. r/Q than bandwidth decreases.

LAXMI said:   8 years ago
Q= R/(2pifL) when R decreases Q also decrease its value. And BW= fr/Q so decrease in the value of Q would increase the BW.

HAris said:   6 years ago
Simply= BW=F/Q.

Q=1/R.√(L/C).

Put in BW,
BW=F/(1/R).
B.W= F*R.

SO, BW is directly proportional to Resistance.


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