Quiz: Chapter 11 - Alternating Current

1 The mean value of A.C. over a complete cycle is

Maximum Minimum Zero None

2 The inductive reactance is:

\( X_L = \omega C \) \( X_L = \omega L \) \( X_L = \frac{1}{\omega C} \) \( X_L = \frac{1}{\omega L} \)

3 At high frequency, the current through a capacitor of AC circuit will be:

Large Small Infinite Zero

4 The highest value reached by the voltage or current in one cycle is called

Peak to peak value Peak value Instantaneous value Root mean square value

5 If the motor is overloaded, then the magnitude of "back emf":

Increases Decreases Constant Becomes zero

6 A capacitor is perfect insulator for:

Alternating current Direct current Both a and b None

7 The process combining low frequency signal with high frequency radio wave is called:

Modulation Amplification Demodulation Resonance

8 In pure resistive AC circuit, instantaneous value of voltage or current:

Current lags behind voltage Current leads voltage by \( \frac{\pi}{2} \) Both are in-phase Voltage leads current by \( \frac{\pi}{2} \)

9 Which of the following requires a material medium for their propagation:

Heat waves X-rays Sound waves Ultraviolet rays

10 In modulation, low frequency signal is known as:

Loaded signal Fluctuated signal Harmonic signal Modulation signal

11 The mutual induction between two coils depends upon:

Area of the coils Number of turns Distance between the coils All of these

12 Pure choke consumes:

Minimum power Maximum power No power Average power

13 To construct a step down transformer:

\( N_S < N_P \) \( N_P < N_S \) \( N_S = N_P \) \( N_S, N_P = 1 \)

14 Power dissipation in pure inductive or in a pure capacitive circuit is:

Infinite Zero Minimum Maximum

15 The practical application of phenomenon of mutual induction is:

Electrical motor Transformer AC generator DC generator

16 There are ______ types of modulations:

1 2 3 4

17 The SI unit of impedance is:

Henry Hertz Ampere Ohm

18 Which of the following is true for a step down transformer:

\( N_p > N_s \) \( N_p < N_s \) \( N_p = N_s \) None of these

19 If \( I_0 \) is the peak value of AC, its average value over the complete cycle is:

\( \frac{I_0}{\sqrt{2}} \) \( \sqrt{2}I_0 \) \( \frac{\sqrt{2}}{I_0} \) zero

20 At resonance, the phase angle for RLC series resonance circuit equals:

\( 0^\circ \) \( 90^\circ \) \( 180^\circ \) \( 270^\circ \)

21 The unit of impedance is:

Ohm \( (Ohm)^{-1} \) \( (Ohm - m)^{-1} \) no unit

22 A device that allows permits flow of DC through the circuit easily, is called:

Inductor Capacitor AC generator Transformer

23 The phase difference between each pair of coils of a three phase AC generator is:

\( 0^\circ \) \( 90^\circ \) \( 120^\circ \) \( 180^\circ \)

24 Main reason for the world wide use of AC is that it can be transmitted to:

Short distances at very low cost Long distances at very high cost Short distances at very high cost Long distances at very low cost

25 If \( V_{rms} = 10\sqrt{2} \) volts, then phase voltage \( V_0 \) will be:

10 volts 20 volts 40 volts \( \frac{10}{\sqrt{2}} \) volts

26 At resonance RLC series circuit shows the behavior of:

Pure resistive circuit Pure capacitive circuit Pure inductive circuit Pure RLC circuit

27 At resonance, the value of current in RLC series circuit is equal to:

\( \frac{V_0}{R} \) \( V_0R \) \( \frac{l}{2} \) zero

28 At high frequency, RLC series circuit shows the behavior of:

Pure inductive circuit Pure resistive circuit Pure capacitive circuit Pure RLC circuit

29 The r.m.s. value of A.C current is

\( 0.707 I_o \) \( 0.707 V_o \) \( 0.707 R_o \) None

30 In pure resistive A.C. circuit the voltage and current are

In phase Voltage leads the current Current leads the voltage None

31 The waves which can also pass through the vacuum are

Matter wave Mechanical wave Electromagnetic wave Transverse wave

32 The unit used for capacitive reactance is

Volt Ampere Joule Ohm

33 Power dissipated in pure inductor is:

Large Small Infinite Zero

34 If the frequency of A.C is large the reactance of capacitor is

Large Small Zero None

35 In case of capacitor, the voltage lags behind the current by

\( 90^\circ \) \( 60^\circ \) \( 30^\circ \) \( 180^\circ \)

36 In the pure inductor the resistance is

Zero Maximum Minimum None

37 In pure inductive circuit the voltage

Leads the current by \( 90^\circ \) Lags the current by \( 90^\circ \) Remains same with current None

38 The reactance of inductor is represented by

Xc XL RL None

39 If the frequency of A.C. is doubled, the reactance of inductor will be

Half Same Double Triple

40 The average power dissipated in a pure inductor is

Maximum Minimum Zero None

41 By increasing the frequency of A.C. through an inductor the reactance will be

Increases Decreases Remain same None

42 In case of phasor diagram the vector rotates

Clockwise Anti clockwise Remain stationary None

43 The combine opposition of resistor, capacitor and inductor is called

Reactance Resistor Impedance None

44 The S.I unit of impedance is called

Joule Weber Ampere Ohm

45 When A.C. flow through RC series circuit the magnitude of voltage is

\( V = I\sqrt{R^2 + X_L^2} \) \( V = I\sqrt{R^2 + X_C^2} \) \( V = IR \) None

46 The magnitude of voltage in case of RL – series circuit

\( V = I\sqrt{R^2 + X_L^2} \) \( V = I\sqrt{R^2 + X_C^2} \) \( V = IR \) None

47 The average power in case of A.C. series circuit is

\( P = VI \) \( P = VI \cos \varphi \) \( P = VI \sin \varphi \) None

48 In equation P = VI \( \cos \varphi \), the factor \( \cos \varphi \) is called

Cosine factor Power factor Phase None

49 The behavior of resistance is frequency

Dependent Independent No response None of these

50 The impedance Z can be expressed as:

\( V_{rms} + I_{rms} \) \( V_{rms} - I_{rms} \) \( V_{rms}/I_{rms} \) \( I_{rms}/V_{rms} \)

51 At resonance frequency the power factor is

One Zero Two Three

52 The frequency at which XL is equal to Xc is called

Resonance frequency Threshold frequency Non-frequency None

53 At resonance frequency the impedance of A.C series circuit is

Maximum Minimum Cannot explain by given data None

54 In parallel RLC circuit, at resonance frequency, there will be maximum

Power Voltage Impedance None

55 The electrical oscillators are used in

Metal detectors Amplifier Diode None

56 Which of the following permits direct current to flow easily?

Resistance Capacitance Inductance None of these

57 A.M stands for

Amplitude Modulation Applied Metal Accurate Measurement None

58 F.M stands for

Frequency Modulation Frequency Metal Frequency Member None

59 The process of combining the low frequency signal with high frequency radio-wave is called

Modulation Amplification Rectification None

60 A capacitor is perfect insulator for:

Alternating current Direct current Both a and b None

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Chapter 11: Alternating Current