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°

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

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

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

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

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

15. The power factor of a purely resistive circuit is

• 1.0
• 0
• 0.1
• 0.5

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

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

• current
• impedance
• power factor

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

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

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

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

21.In a series resonance circuit

• L = C
• L = R
• XL = XC
• R = L = C

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

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°

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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