Objective Questions on Steady-State Analysis

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Objective Questions on Steady-State Analysis

Objective Questions on Steady-State Analysis of AC Circuits, MCQ on Steady-State Analysis of AC Circuits, Objective Questions on steady-state analysis of R-L, R-C, R-L-C series network, Multiple Choice Questions (MCQ) on R-L, R-C and R-L-C circuits.

Multiple Choice Questions on AC circuit analysis

  1. The voltage and current in an AC circuit is represented by u = Vm sin (wt + 30°) and i = Im sin (wt − 45°). The power factor angle of the circuit is
  • 15°
  • 75°
  • 45o
  • 30°

Answer: 75°

2. A current is represented by i = 100 sin (314t − 30°) A. The rms value of the current and the frequency are, respectively

  • 100 A and 314 Hz
  • 100 A and 50 Hz
  • 70.7 A and 314 Hz
  • 707 A and 50 Hz

Answer: 707 A and 50 Hz

3. A current of 10 A is flowing through a circuit. The power factor is 0.5 lagging. The instantaneous value of the current can be written as

  • i = 10 sin 60° A
  • i = 10 sin (ωt − 30°) A
  • i = 14.14 sin (ωt − 60°) A
  • i = 14.14 sin (ωt + 60°) A

Answer: i = 14.14 sin (ωt − 60°) A

4. In a purely inductive circuit

  • current lags the voltage by 90°
  • current leads the voltage by 90°
  • voltage lags the current by 90°
  • current lags the voltage by 180°

Answer: current lags the voltage by 90°

5. Form factor of an AC wave indicates

  • Low sharp or steep the wave shape is
  • Low flat the wave shape is
  • Low symmetrical the wave shape is
  • The degree of its conformity to sinusoidal form

Answer: Low sharp or steep the wave shape is

6. Power consumed by a pure inductor is

  • infinite
  • very high
  • zero
  • very small

Answer: zero

7. If form factor of a sinusoidal wave is 1.11, then the form factor of a triangular wave will

  • also be 1.11
  • be less than 1.11
  • be more than 1.11
  • be 1

Answer: be more than 1.11

8. A voltage of v = 100 sin (314t − 30°) is connected across a 10-Ω resistor. The power dissipated in the circuit will be

  • 100000 W
  • 1000 W
  • 500 W
  • 250 W

Answer: 500 W

9. The average value of a sinusoidal current is

  • \frac{2I_{m}}{\pi}
  • \frac{I_{m}}{\pi}
  • \frac{I_{m}}{2\pi}
  • \frac{I_{m}^{2}}{2\pi}

Answer: \frac{2I_{m}}{\pi}

10. Form factor of an alternating wave form is the ratio of

  • rms value and average value
  • Average value and rms value
  • Maximum value and average value
  • Maximum value and rms value

Answer: rms value and average value

11. A capacitance of C farad is connected to a 230V, 50 Hz supply. The value of capacitive reactance is

  • 314 C \Omega
  • \frac{1}{314 C} \Omega   
  • 628 C \Omega
  • \frac{1}{628 C} \Omega

Answer: \frac{1}{314 C} \Omega   

12. The form factor of a square wave is

  • 1.11
  • 1.0
  • 0
  • 1.414

Answer: 1.0

13. Two sinusoidal waves are represented as v1 = 100 sin (ωt + 30°) and v2 = 200 sin (ωt − 60°). The phasor relationship between the voltages can be expressed as

  • v1 lags v2 by 90°
  • v2 lags v1 by 90°
  • v1 lags v2 by 30°
  • v2 lags v1 by 60°

Answer: v2 lags v1 by 90°

14. Inductive reactance of coil of 0.1 H at 50 Hz is

  • 31.4 Ω
  • 62.8 Ω
  • 314 Ω
  • 5 Ω

Answer: 31.4 Ω

15. The power factor of a purely resistive circuit is

  • 1.0
  • 0
  • 0.1
  • 0.5

Answer: 1.0

16. A series RLC circuit has R = 50 Ω, L = 50 μH and C = 2 μF. The Q-factor of the circuit is

  • 0.1
  • 1
  • 10
  • 2

Answer: 0.1

17. When a parallel circuit is in resonance, which of the following of the circuit is maximum?

  • current
  • impedance
  • admittance
  • power factor

Answer: impedance

18. In a series resonant circuit, a change in supply voltage will cause a change in

  • the current drawn,
  • the Q-factor of the circuit,
  • the bandwidth of the circuit,
  • the resonant frequency as well

Answer: the current drawn

19. Which of the following conditions is true for both series and parallel resonance?

  • impedance is minimum
  • power factor is unity
  • power factor is zero
  • power is low

Answer: power factor is unity

20. The product of voltage and current in an AC circuit is called

  • active power
  • apparent power
  • average power
  • reactive power

Answer: apparent power

21.In a series resonance circuit

  • L = C
  • L = R
  • XL = XC
  • R = L = C

Answer: XL = XC

22. Two impedances Z1 = 4 + j4 Ω and Z2 = 4 − j4 Ω are connected in parallel. Their equivalent impedance is

  • 8 + j8 Ω
  • 4 + j0 Ω
  • 8 − j8 Ω
  • 8 + j0 Ω

Answer: 4 + j0 Ω

23.When an inductance L and a resistance R are connected in parallel across an AC supply, the current drawn by the two parallel branches will be out of phase by

  • 90°
  • 180°
  • 45°

Answer: 90°

24. The resonant frequency in R-L-C series circuit is

  • f_{0}=\frac{2\pi }{\sqrt{LC}}
  • f_{0}=\frac{\sqrt{LC} }{2\pi }
  • f_{0}=\frac{1 }{2\pi \sqrt{LC}}
  • f_{0}=\frac{1}{2\pi }\sqrt{\frac{L }{C}}

Answer: f_{0}=\frac{1 }{2\pi \sqrt{LC}}

25. The bandwidth of a series R-L-C circuit is

  • \frac{C}{2\pi L}
  • \frac{R}{2\pi L}
  • \frac{C}{2\pi R}
  • \frac{L}{2\pi R}

Answer: \frac{R}{2\pi L}

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