Series Parallel RLC Circuit MCQ

1. When a sinusoidal voltage is applied across R – L series circuit having R = XL, the phase angle will be

(a) 90^o
(b) 45^o lag
(c) 45^o leading
(d) 90^o leading

2. An ac source of 200 V RMS supplies active power of 600 W and reactive power of 800 VAR. The RMS current drawn from the source is

(a) 10 A
(b) 5 A
(c) 3.75 A
(d) 2.5 A

3. If the power dissipated in the circuit shown in the Figure is 8 W, then the value of E will be

(a) 2V
(b) 4 V
(c) 8 V
(d) 16 V

4. When a sinusoidal voltage is applied across R – L parallel so that R = X_L the phase angle will be

(a) 45^o lagging
(b) 45^o leading
(c) 90^o lagging
(d) 90^o leading

5. A voltage of V = 100 ∠ 30^o is applied to an impedance Z = 3 + j4. Which one of the following is the power triangle?

(a)
(b)
(c)
(d)

6. Capacitive susceptance is a measure of

(a) a purely capacitive circuit’s ability to pass current.
(b) a purely capacitive circuit’s ability to resist the flow of current.
(c) the extent of neutralization of reactive power in a circuit.
(d) reactive power in a circuit.

7. A resistance of R ohm and inductance of L Henery are connected across 240 V, 50 Hz supply. Power dissipated in the circuit is 100 W and the voltage across R is 100 V. In order to improve the PF to unity, the capacitor that is to be connected in series should have value of

(a) 43.7 µF
(b) 4.37 µF
(c) 437 µF
(d) 4.37 µF

8. In an RLC circuit, supplied from AC source, the reactive power is proportional to the

(a) average energy stored in the electric field.
(b) average energy stored in the magnetic field.
(c) sum of the average energy stored in the electric field and that stored in the magnetic field.
(d) difference between the average energy stored in the electric field and that stored in the magnetic field.

9. Real part of admittance is ……… and the imaginary part is ……

(a) impedance, resistance
(b) resistance, impedance
(c) susceptance, inductance
(d) conductance, susceptance

10. In an AC circuit if voltage V = (a + jb) and current I = (c + jd).

Then the power is given by

(a) ac + ad
(b) ac + bd
(c) bc – ad
(d) bc + ad

11. A square wave is fed to an R – C circuit. Then

(a) voltage across R is square and across C is not square.
(b) voltage across C is square and across R is not square.
(c) voltage across both R and C is square.
(d) voltage across both R and C is not square.

12. A 100 W, 100 V bulb is to be supplied from 220 V, 50 Hz supply. Which of the following arrangements is preferable?

(a) Additional pure inductance in series with lamp.
(b) Additional resistance in series with the lamp.
(c) Additional inductance and capacitance in series with the lamp.

13. With the increase in applied frequency, the dielectric loss in a material will

(a) increase.
(b) decrease.
(c) remain constant.

14. Under the condition of resonance in R-L-C series circuit, the power factor of the circuit is

(a) 0.5 lagging.
(b) 0.5 leading.
(c) unity.
(d) zero.

15. The current through a series RLC circuit under resonance condition will be

(a) V/R
(b) V/X_C
(c) V/X_L
(d) none of these

16. Consider the following statements

When a series R-L-C circuit is under resonance

1. current is maximum through R.
2. magnitude of the voltage across L is equal to that across C.
3. the power factor of the circuit is unity.

Which of the statements given above are correct?
(a) 1, 2 and 3
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1 and 3 only

17. At resonant frequency an R-L-C circuit draws maximum current due to the reason that

(a) the difference between capacitive reactance and inductive reactance is zero.
(b) the impedance is more than resistance.
(c) the voltage across the capacitor equals the applied voltage.
(d) the power factor is less than unity.

18. Consider the following statements with respect to a series R-L-C circuit under resonance condition:

1. All the applied voltage appears across R.
2. There is no voltage across either L or C.
3. The voltage across L and C equal and equal to their maximum values.

Out of these statements
(a) 1 alone is correct.
(b) 2 alone is correct.
(c) 1 and 3 are correct.
(d) 1 and 2 are correct.

19. A series R-L-C circuit will have unity power factor is operated at a frequency of

(a) 1/LC
(b) 1/ω√(LC)
(c) 1/ ω²LC
(d) 1/2π√(LC)

20. Consider the following statements:

In a network of resonance

1. The admittance is maximum.
2. The power factor is unity irrespective of the network.
3. The Q of a series RLC resonant circuit is independent of R.

Out of these statements
(a) 1 and 3 are correct.
(b) 1 and 2 are correct.
(c) 2 and 3 are correct.
(d) 1 alone is correct.

21. A circuit with a resistor, inductor and capacitor in series is resonant of f_o Hz. If the all component values are now doubled the new resonant frequency is

(a) 2f_o
(b) Still f_o
(c) f_o/4
(d) f_o/2

22. In a series RLC circuit at resonance, the magnitude of voltage devolped across the capacitor

(a) is always zero.
(b) can never be greater than the input voltage.
(c) can be greater than the input voltage however, it is 90^o out of phase with the input voltage.
(d) can be greater than the input voltage and is in phase with the input voltage.

23. A coil having a resistance of 5Ω and inductance of 0.1 H is connected with a condenser of capacitance 50 µF. A constant alternating voltage of 200 V is applied to the circuit. The voltage across the coil at resonance is

(a) 200 V
(b) 1788 V
(c) 1800 V
(d) 2000 V

24. In a series RLC circuit, the maximum voltage across the capacitor occurs at a frequency

(a) double the resonant frequency.
(b) equal to the resonant frequency.
(c) √2 times the resonant frequency.
(d) below the resonant frequency.

25. In a series RLC circuit, the maximum voltage across the inductor occurs frequency

(a) at resonant the frequency.
(b) just after the resonant frequency.
(c) just before the resonant frequency.
(d) just before and after the resonant frequency.

26. A series circuit having a resonant frequency of 60 KHz is connected in series with a signal generator which produces signals of frequencies of 20, 30, 40 and kHz. The signals experiencing minimum and maximum impedances will be

(a) 60 kHz and 20 kHz respectively.
(b) 20 kHz and 60 kHz respectively.
(c) 30 kHz and 60 kHz respectively.
(d) 20 kHz and 40 kHz respectively.

27. Q – factor of a series RLC circuit possessing resonant frequency of 10 Hz and bandwidth of 5 Hz is

(a) 0.5
(b) 2
(c) 2.5
(d) 50

28. When Q – factor of a circuit is high, then

(a) power factor of the circuit is high.
(b) impedance of the circuit is high.
(c) bandwidth is large.
(d) none of these.

29. A high Q coil has

(a) large bandwidth.
(b) high losses.
(c) low losses.
(d) flat response.

30. In a series resonant circuit, with the increase in L

(a) resonant frequency will decrease.
(b) bandwidth will decrease.
(c) Q will increase.
(d) all of the above.

31. In a series resonant circuit, with the increase in C

(a) resonant frequency will decrease.
(b) Q will decrease.
(c) bandwidth will decrease.
(d) both (a) and (b).

32. Which of the following will not be affected due to change in R?

(a) Bandwidth
(b) Q
(c) Resonant frequency
(d) None

33. Change in circuit voltage will affect

(a) Resonant frequency
(b) Q
(c) Current
(d) Bandwidth

34. Higher the Q of a series circuit, narrower its

(a) pass-band.
(b) resonant curve.
(c) bandwidth.
(d) all of these.

35. An RLC series circuit has f₁ and f₂ as the half power frequencies and f_o as the resonant frequency. The Q factor of the circuit is given by

(a) (f₁ + f₂)/2f_o
(b) (f₁ – f_o)/(f₂ – f_o)
(c) f_o/(f₁ – f₂)
(d) (f₁ – f₂)/f_o

36. Resonant frequency f_r of a series RLC circuit is related to half power frequencies f₁ and f₂ as

(a) f_r = (f₁ + f₂)/2
(b) f_r = √(f₁f₂)
(c) f_r = f₂ – f₁
(d) f_r = √f₁ + √f₂

37. An RLC series circuit has f₁ and f₂ the half power frequencies and f_r as the resonant frequency. The selectivity of the circuit is given by

(a) (f₁ + f₂)/f_r
(b) (f₂ – f₁)/2f_r
(c) (f₂ – f₁)/f_r
(d) None of these

38. In an RLC resonant circuit, if inductance of the circuit is made double and the capacitance is made half, which of the following will be affected?

(a) Resonant frequency.
(b) Selectivity of the circuit.
(c) Current at resonant frequency.
(d) Impedance at resonant frequency.

39. At resonance, the parallel circuit of Figure below constituted by an iron-cored coil and a capacitor behaves like:

(a) an open circuit.
(b) a short circuit.
(c) a pure resistor of value R
(d) a pure value of resistor of value much higher than R.

40. When resonant frequency of an RLC parallel circuit is given by 1/2π√(LC), the essential condition is that

(a) impedance must be non-resistive.
(b) capacitance must be non-leaky.
(c) current is minimum at resonance.
(d) all of the above.

41. The resistance of parallel resonant circuit is given by

(a) LC/R_L
(b) LCR_L
(c) C/(LR_L)
(d) L/(CR_L)

42. A parallel circuit is said to be in resonance when the admittance is purely

(a) capacitive.
(b) inductive.
(c) susceptive.
(d) conductive.

43. In order to tune a parallel resonant circuit to a lower frequency, the capacitance must

(a) be increased.
(b) be decreased.
(c) be zero.
(d) remain the same.

44. Consider the following statements:

If a high Q parallel resonant circuit is loaded, then

1. the circuit impedance reduces.
2. the resonant frequency reduces.
3. the bandwidth reduces.

Which of the statements given above is/are correct?
(a) 1 and 2 only.
(b) 1 only.
(c) 2 and 3 only.
(d) 1, 2 and 3.

45. A circuit has two parallel branches. In one branch, R and L are connected in series while in the other R and C are connected in series. If R = √(L/C), which one of the following is not correct?

(a) The circuit is in resonance.
(b) The two branch currents are in quadrature.
(c) The circuit has impedance independent of its frequency.
(d) The two branch currents are in phase.

46. For a parallel RLC circuit, if R = 40 Ω, L = 2 H and C = 0.5 F, the bandwidth and quality factor are respectively

(a) 20 rad/s, 0.05
(b) 10 rad/s, 20
(c) 20 rad/s, 10
(d) 0.05 rad/s, 20

47. A parallel resonant circuit can be employed

(a) as a high impedance.
(b) to reject a small band of frequencies.
(c) to amplify voltage.
(d) both (a) and (b).

48. In series as well as parallel resonant circuit, increase in resistance would cause

(a) increase in bandwidth of both the circuits.
(b) decrease in bandwidth of both the circuits.
(c) decrease in bandwidth in series circuit and increase in bandwidth in parallel circuit.
(d) increase in bandwidth in series circuit and decrease in bandwidth in parallel circuit.

49. The frequency at which maximum voltage occurs across the inductance in an R-L- C circuit is

50. The frequency at which maximum voltage occurs across the capacitance in an R-L- C circuit is

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