EEE - RLC Circuits and Resonance Quiz (or) MCQ

1 .

_________ the resonant frequency, the current in the inductor lags the voltage in a series RLC circuit.

A)

Above

B)

Below

C)

Equal to

D)

Depends on the circuit

Correct Answer : Above

Explanation : The current in the inductor lags the voltage in a series RLC circuit if a circuit is inductive dominant i.e. if X_L > X_C
ω_L > 1/ω_C => ω > 1/√LC => ω > ω₀.
So, the current in the inductor lags the voltage in a series RLC circuit above the resonant frequency.

2 .

In a series RLC circuit, the phase difference between the current in the capacitor and the current in the resistor is?

A)

0â°

B)

90â°

C)

180â°

D)

360â°

Correct Answer : 0â°

Explanation : In a series RLC circuit, the phase difference between the current in the capacitor and the current in the resistor is 0⁰ because same current flows in the capacitor as well as the resistor.

3 .

Resonance is a condition in a series RLC circuit in which the capacitive and inductive reactances are equal in magnitude.

A)

True

B)

False

C)

Can Not Say

D)

None of the above

Correct Answer : True

4 .

A certain series resonant circuit has a bandwidth of 2 kHz. If the existing coil is replaced with one having a higher value of Q, the bandwidth will

A)

Increase

B)

Decrease

C)

Remain the same

D)

Be less selective

Correct Answer : Decrease

5 .

A 6.8 kΩ resistor, a 7 mH coil, and a 0.02 µF capacitor are in parallel across a 17 kHz ac source. The coil's internal resistance, R_W, is 30 Ω. The equivalent parallel resistance, R_p(eq), is

A)

626 Ω

B)

1,878 Ω

C)

18,750 Ω

D)

18,780 Ω

Correct Answer : 18,780 Ω

6 .

The impedance at the resonant frequency of a series RLC circuit with L = 20 mH, C = 0.02 µF, and RW = 90 Ω is

A)

0 Ω

B)

20 Ω

C)

40 Ω

D)

90 Ω

Correct Answer : 90 Ω

7 .

In a parallel RLC circuit, the smaller reactance determines the net reactance of the circuit.

A)

True

B)

False

C)

Can Not Say

D)

None of the above

Correct Answer : True

8 .

The reactive voltages, V_L and V_C, cancel at resonance.

A)

True

B)

False

C)

Can not Say

D)

None of the above

Correct Answer : True

9 .

To tune a parallel resonant circuit to a higher frequency, the capacitance should be

A)

Increased

B)

Decreased

C)

Left alone

D)

Replaced with inductance

Correct Answer : Decreased

10 .

In a series RLC circuit, the larger reactance determines the net reactance of the circuit.

A)

True

B)

False

C)

Can Not Say

D)

None of the above

Correct Answer : True

11 .

In a series RLC circuit, the phase difference between the current in the capacitor and the current in the inductor is?

A)

0â°

B)

90â°

C)

180â°

D)

360â°

Correct Answer : 0â°

Explanation : In a series RLC circuit, the phase difference between the current in the inductor and the current in the capacitor is 0⁰ because same current flows in the inductor as well as the capacitor.

12 .

A 15 Ω resistor, an inductor with 8 Ω inductive reactance, and a capacitor with 12 Ω capacitive reactance are in parallel across an ac voltage source. The circuit impedance is

A)

12.7 Ω

B)

127 Ω

C)

4,436 Ω

D)

6,174 Ω

Correct Answer : 12.7 Ω

13 .

A 9 mH coil is in parallel with a 0.015 µF capacitor across an 18 kHz ac source. The coil's internal resistance R_W, is 60 Ω. The circuit impedance is

A)

290 Ω

B)

1,018 Ω

C)

1,734 Ω

D)

17,340 Ω

Correct Answer : 17,340 Ω

14 .

A 200 Ω resistor, a coil with 30 Ω of reactance, and a capacitor of unknown reactance are in series across an ac source. The circuit is at resonance. Circuit impedance is

A)

170 Ω

B)

230 Ω

C)

200 Ω

D)

Cannot be determined

Correct Answer : 200 Ω

15 .

A 15 Ω resistor, a 220 µH coil, and a 60 pF capacitor are in series across an ac source. What is the bandwidth of the circuit?

A)

138 kHz

B)

138 MHz

C)

1,907 Hz

D)

10,866 Hz

Correct Answer : 10,866 Hz

16 .

In a series RLC circuit, the current is minimum at resonance.

A)

True

B)

False

C)

Can Not Say

D)

None of the above

Correct Answer : False

17 .

A series resonant circuit is commonly called a tank circuit.

A)

True

B)

False

C)

Can Not Say

D)

None of the above

Correct Answer : False

18 .

A 10 Ω resistor, a 90 mH coil, and a 0.015 µF capacitor are in series across an ac source. The impedance magnitude at 1,200 Hz below f_r is

A)

1,616 Ω

B)

161 Ω

C)

1,771 Ω

D)

3,387 Ω

Correct Answer : 1,616 Ω

19 .

In a series RLC circuit, the phase difference between the current in the inductor and the current in the resistor is?

A)

0â°

B)

90â°

C)

180â°

D)

360â°

Correct Answer : 0â°

Explanation : In a series RLC circuit, the phase difference between the current in the inductor and the current in the resistor is 0⁰ because same current flows in the inductor as well as the resistor.

20 .

In a series RLC circuit, the phase difference between the current in the circuit and the voltage across the resistor is?

A)

0â°

B)

90â°

C)

180â°

D)

360â°

Correct Answer : 0â°

Explanation : In a series RLC circuit, the phase difference between the voltage across the resistor and the current in the circuit is 0⁰ because they are in phase.

21 .

In a series RLC circuit, the phase difference between the current in the circuit and the voltage across the capacitor is?

A)

0â°

B)

90â°

C)

180â°

D)

360â°

Correct Answer : 90Â°

Explanation : In a series RLC circuit, voltage across capacitor lags the current in the circuit by 90⁰ so, the phase difference between the voltage across the capacitor and the current in the circuit is 90⁰.

22 .

________ the resonant frequency, the current in the capacitor leads the voltage in a series RLC circuit.

A)

Above

B)

Below

C)

Equal to

D)

Depends on the circuit

Correct Answer : Below

23 .

If the resistance in parallel with a parallel resonant circuit is reduced, the bandwidth

A)

Disappears

B)

Increases

C)

Decreases

D)

Becomes sharper

Correct Answer : Decreases

24 .

If the value of C in a series RLC circuit is decreased, the resonant frequency

A)

Increases

B)

Decreases

C)

Is reduced to zero

D)

Is not affected

Correct Answer : Increases

25 .

A certain series RLC circuit with a 200 Hz, 15 V ac source has the following values: R = 12 Ω, C = 80 µF, and L = 10 mH. The total impedance, expressed in polar form, is

A)

12.28 ∠12.34° Ω

B)

9.95 ∠12.34° Ω

C)

12.57 ∠12.34° Ω

D)

12.62 ∠12.34° Ω

Correct Answer : 12.28 ∠12.34° Ω

26 .

In a series RLC circuit that is operating above the resonant frequency, the current

A)

Is zero

B)

Leads the applied voltage

C)

Is in phase with the applied voltage

D)

Lags the applied voltage

Correct Answer : Lags the applied voltage

27 .

At series resonance, the inductive reactance and capacitive reactance are never equal.

A)

True

B)

False

C)

Can Not Say

D)

None of the above

Correct Answer : False

28 .

A 90 Ω resistor, a coil with 30 Ω of reactance, and a capacitor with 50 Ω of reactance are in series across a 12 V ac source. The current through the resistor is

A)

9 mA

B)

13 mA

C)

90 mA

D)

130 mA

Correct Answer : 130 mA

29 .

The quality factor (Q) is the ratio of true power to apparent power.

A)

True

B)

False

C)

Can Not Say

D)

None of the above

Correct Answer : False

30 .

A 24 Ω resistor, an inductor with a reactance of 120 Ω, and a capacitor with a reactance of 120 Ω are in series across a 60 V source. The circuit is at resonance. The voltage across the inductor is

A)

30 V

B)

60 V

C)

300 V

D)

660 V

Correct Answer : 300 V

31 .

A 12 Ω resistor, a 40 µF capacitor, and an 8 mH coil are in series across an ac source. The resonant frequency is

A)

10 kHz

B)

28.1 Hz

C)

281 Hz

D)

2,810 Hz

Correct Answer : 281 Hz

32 .

A resistor of 3 kΩ, a 0.05 µF capacitor, and a 120 mH coil are in series across a 5 kHz, 20 V ac source. What is the impedance, expressed in polar form?

A)

433 Ω

B)

636 Ω

C)

3,769 Ω

D)

4,337 Ω

Correct Answer : 4,337 Ω

33 .

In a certain series resonant circuit, V_C = 125 V, V_L = 125 V, and V_R = 40 V. The value of the source voltage is

A)

40 V

B)

125 V

C)

250 V

D)

290 V

Correct Answer : 40 V

34 .

X_L and X_C have opposing effects in an RLC circuit.

A)

True

B)

False

C)

Can Not Say

D)

None of the above

Correct Answer : True

35 .

A resonant circuit has a lower critical frequency of 7 kHz and an upper critical frequency of 13 kHz. The bandwidth of the circuit is

A)

4 kHz

B)

7 kHz

C)

13 kHz

D)

20 kHz

Correct Answer : 4 kHz