1. If the resonant frequency in a series RLC circuit is 50kHz along with a bandwidth of 1kHz, find the quality factor.
A. 5
B. 50
C. 100
D. 500
Answer: B
We know that the Quality factor is equal to the resonant frequency divided by the bandwidth.
Q = fres/Bandwidth
= 50/1 = 50.
2. What is the SI unit for quality factor?
A. Hz
B. kHz
C. MHz
D. No unit
Answer: D
We know that the Quality factor is equal to the resonant frequency divided by the bandwidth. It is one frequency divided by another hence it has no unit.
3. What happens to the quality factor when the bandwidth increases?
A. Increases
B. Decreases
C. Remains the same
D. Becomes zero
Answer: B
Q = frequency/Bandwidth
The quality factor is inversely proportional to bandwidth. So, if bandwidth increases quality factor decreases.
4. What happens to the quality factor when resonant frequency increases?
A. Increases
B. Decreases
C. Remains the same
D. Becomes zero
Answer: A
Q = frequency/Bandwidth
The quality factor is directly proportional to the resonant frequency. So, if resonant frequency increases quality factor increases.
5. Resonance frequency occurs when ________
A. XL = XC
B. XL>XC
C. XL<xC
D. Cannot be determined
Answer: A
The frequency of a system is said to be resonating when the value of the capacitive reactance and the inductive reactance is the same.
6. The current leads the supply voltage in a series RLC circuit has its frequency _________ the resonant frequency.
A. Above
B. Below
C. Equal to
D. Cannot be determined
Answer: B
Current is leading the voltage indicates capacitor dominating circuit.
XC>XL = > 1/(ωC. > ωL = > ω<1/√LC
So, the frequency is less than the resonant frequency.
7. What is the power factor of a series RLC circuit under resonance conditions?
A. 0
B. 1
C. Infinity
D. 100
Answer: B
The power factor for a series RLC circuit in resonance condition is always unity because the current is in phase with the voltage under resonance condition.
Φ = 00 = > cos ϕ = 1
i.e. power factor = 1.
8. The current lags the supply voltage in a series RLC circuit has its frequency _________ the resonant frequency.
A. Above
B. Below
C. Equal to
D. Cannot be determined
Answer: A
Current is lagging the voltage indicates inductor dominating circuit.
XC < XL = > 1/(ωC. < ωL = > ω > 1/√LC
So, frequency more than resonant frequency.
9. What is the correct formula for quality factors?
A. Q = BW × fr
B. Q = BW/fr
C. Q = fr/BW
D. Q = fr2
Answer: C
The correct formula for quality factor is Q = fr/BW,
where fr is the resonant frequency,
BW is the bandwidth frequency
Q is the quality factor.
10. Quality factor is also known as _________
A. Voltage magnification
B. Current magnification
C. Resistance magnification
D. Impedance magnification
Answer: A
The quality factor is also known as voltage magnification because the voltage across the capacitor or inductor in the resonance condition is equal to Q times the source voltage.
