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Unit 2: Fundamentals of A.C. circuits - Practice Quiz

ECE131 — Basic Electrical And Electronics Engineering 60 Questions
0 Correct 0 Wrong 60 Left
0/60

1 Which statement best describes an alternating current?

Alternating current and voltage Easy
A. It flows in one direction with constant magnitude
B. It remains zero during every complete cycle
C. It changes magnitude and direction periodically
D. It changes magnitude but never changes direction

2 In common AC circuit notation, what do the lowercase symbols and usually represent?

Concept of notations (i, v, I, V) Easy
A. Average current and voltage
B. Instantaneous current and voltage
C. RMS current and voltage
D. Maximum current and voltage

3 For the voltage V, what is the amplitude?

Amplitude Easy
A. V
B. V
C. V
D. V

4 What is the phase angle of ?

Phase Easy
A.
B.
C.
D.

5 If and , how does relate to ?

Phase difference Easy
A. lags by
B. is opposite to by
C. leads by
D. is in phase with

6 What is the RMS value of a sinusoidal voltage with peak value ?

RMS value of an AC signal Easy
A.
B.
C.
D.

7 What is the average value of a pure sinusoidal current over one complete cycle?

Average value of an AC signal Easy
A.
B.
C.
D. Zero

8 What is the complex impedance of an ideal inductor?

Complex representation of impedance Easy
A.
B.
C.
D.

9 In a series RL circuit supplied by a sinusoidal voltage, how does the current relate to the supply voltage?

Steady-state analysis of RL circuits Easy
A. Current is always zero
B. Current is opposite to the voltage
C. Current lags the voltage
D. Current leads the voltage

10 In a series RC circuit supplied by a sinusoidal voltage, how does the current relate to the supply voltage?

Steady-state analysis of RC circuits Easy
A. Current is opposite to the voltage
B. Current leads the voltage
C. Current is always zero
D. Current lags the voltage

11 What is the total impedance of a series RLC circuit?

Steady-state analysis of series RLC circuits Easy
A.
B.
C.
D.

12 What condition produces resonance in a series RLC circuit?

Resonance in series RLC circuit Easy
A.
B.
C.
D.

13 What type of power factor does a series RL circuit have?

Power factor and power calculation in RL circuits Easy
A. Negative power factor
B. Zero power factor
C. Leading power factor
D. Lagging power factor

14 What type of power factor does a series RC circuit have?

Power factor and power calculation in RC circuits Easy
A. Lagging power factor
B. Zero power factor
C. Leading power factor
D. Negative power factor

15 Which formula gives the active power in a single-phase RLC circuit?

Power factor and power calculation in RLC circuits Easy
A.
B.
C.
D.

16 In a balanced three-phase system, what is the phase displacement between adjacent phase voltages?

Three-phase circuits Easy
A.
B.
C.
D.

17 Which set is commonly used to identify the three phase conductors of a three-phase supply?

Numbering and interconnection of three phases Easy
A. , , and
B. , , and
C. , , and
D. , , and

18 How are the three phase windings connected in a delta connection?

Delta or mesh connection Easy
A. End to end in a closed loop
B. Together at one neutral point
C. In parallel across one phase
D. Separately without interconnection

19 For a balanced star-connected network, what is the relation between line voltage and phase voltage ?

Relations between line and phase voltages and currents in star networks Easy
A.
B.
C.
D.

20 For a balanced delta-connected network, what is the relation between line current and phase current ?

Relations between line and phase voltages and currents in delta networks Easy
A.
B.
C.
D.

21 A sinusoidal voltage completes 250 cycles in 5 seconds. What are its frequency and time period?

Alternating current and voltage Medium
A. and
B. and
C. and
D. and

22 In AC circuit notation, and are given. What do and represent, respectively?

Concept of notations (i, v, I, V) Medium
A. Maximum current and average current
B. Average current and maximum current
C. Instantaneous current and RMS current
D. RMS current and instantaneous current

23 For the voltage , what is the amplitude of the equivalent single sinusoid?

Amplitude Medium
A.
B.
C.
D.

24 At , the signal has what instantaneous value and initial trend?

Phase Medium
A. and increasing
B. and decreasing
C. and increasing
D. and decreasing

25 Given and , what is the phase relationship between voltage and current?

Phase difference Medium
A. Voltage leads current by
B. Voltage leads current by
C. Current leads voltage by
D. Current leads voltage by

26 A symmetrical square-wave current alternates between and for equal time intervals. What is its RMS value?

RMS value of an AC signal Medium
A.
B.
C.
D.

27 A sinusoidal current has a peak value of . What is its average value over one positive half-cycle?

Average value of an AC signal Medium
A.
B.
C.
D.

28 An impedance is given by . Which polar representation and circuit behavior are correct?

Complex representation of impedance Medium
A. , capacitive
B. , inductive
C. , capacitive
D. , inductive

29 A series RL circuit with and is connected to a RMS supply. What is the current phasor when the supply voltage is the reference?

Steady-state analysis of RL circuits Medium
A.
B.
C.
D.

30 A series RC circuit has , , and an applied voltage of RMS. What is the supply current?

Steady-state analysis of RC circuits Medium
A.
B.
C.
D.

31 A series RLC circuit has , , and . If the applied voltage is RMS, what is the current?

Steady-state analysis of series RLC circuits Medium
A.
B.
C.
D.

32 A series RLC circuit has and . Approximately at what frequency does resonance occur?

Resonance in series RLC circuit Medium
A.
B.
C.
D.

33 A series RL load with and is connected to a RMS supply. What are its power factor and real power?

Power factor and power calculation in RL circuits Medium
A. leading and
B. lagging and
C. leading and
D. lagging and

34 A series RC load has and across a RMS supply. What are its power factor and real power?

Power factor and power calculation in RC circuits Medium
A. lagging and
B. leading and
C. leading and
D. lagging and

35 A series RLC load has , , and . It is connected to a RMS supply. What are the power factor and real power?

Power factor and power calculation in RLC circuits Medium
A. leading and
B. leading and
C. lagging and
D. lagging and

36 A balanced three-phase load draws a line current of from a line-to-line supply at a power factor of . What is the total real power?

Three-phase circuits Medium
A.
B.
C.
D.

37 Three phase voltages are , , and . What is their phase sequence?

Numbering and interconnection of three phases Medium
A.
B.
C.
D.

38 Three identical impedances are connected in delta across a balanced three-phase supply. If each impedance has magnitude , what is the magnitude of the line current?

Delta or mesh connection Medium
A.
B.
C.
D.

39 A balanced star-connected load has a phase voltage of and a phase current of . What are the corresponding line voltage and line current?

Relations between line and phase voltages and currents in star networks Medium
A. and
B. and
C. and
D. and

40 A balanced delta-connected load draws a line current of from a three-phase supply. What are the phase voltage and phase current?

Relations between line and phase voltages and currents in delta networks Medium
A. and
B. and
C. and
D. and

41 A periodic voltage is given by V. If is the fundamental period of , which expression represents ?

Alternating current and voltage Hard
A. V
B. V
C. V
D. V

42 Using the conventional RMS phasor notation with cosine as reference, the instantaneous current is A. Which statement is correct?

Concept of notations (i, v, I, V) Hard
A. A and A
B. A and A
C. A and A
D. A and A

43 A nonsinusoidal voltage is V. What is the amplitude of its fundamental component?

Amplitude Hard
A. V
B. V
C. V
D. V

44 Express V in the standard form with and . What is ?

Phase Hard
A.
B.
C.
D.

45 Voltage leads voltage by , and current lags by . What is the phase relationship between and ?

Phase difference Hard
A. leads by
B. leads by
C. leads by
D. leads by

46 Over each period , a voltage equals V for , V for , and V for . What is its RMS value?

RMS value of an AC signal Hard
A. V
B. V
C. V
D. V

47 For , what is the average value over the first quarter-cycle, ?

Average value of an AC signal Hard
A.
B.
C.
D.

48 Two impedances and are connected in parallel. What is their equivalent impedance?

Complex representation of impedance Hard
A.
B.
C.
D.

49 A series RL circuit has and . It is supplied by V. What is the steady-state current?

Steady-state analysis of RL circuits Hard
A. A
B. A
C. A
D. A

50 A series RC circuit with and is connected to V RMS. What is the capacitor-voltage phasor?

Steady-state analysis of RC circuits Hard
A. V
B. V
C. V
D. V

51 A series RLC circuit has , , and . With V RMS, what is the phasor voltage across the series combination of and ?

Steady-state analysis of series RLC circuits Hard
A. V
B. V
C. V
D. V

52 A series RLC circuit has , mH, and F. Which pair gives its lower and upper half-power angular frequencies?

Resonance in series RLC circuit Hard
A. rad/s and rad/s
B. rad/s and rad/s
C. rad/s and rad/s
D. rad/s and rad/s

53 A series RL load takes kW from a V RMS supply at a power factor of lagging. What is the load impedance?

Power factor and power calculation in RL circuits Hard
A.
B.
C.
D.

54 A series RC load has and and is connected to a V RMS supply. What is its complex power?

Power factor and power calculation in RC circuits Hard
A. VA
B. VA
C. VA
D. VA

55 A series RLC load has , , and . It is supplied at V RMS. Which set of power quantities is correct?

Power factor and power calculation in RLC circuits Hard
A. kW, kvar, power factor
B. kW, kvar, power factor lagging
C. kW, kvar, power factor leading
D. kW, kvar, power factor lagging

56 In an unbalanced four-wire star load, the phase currents from source to load are A, A, and A. What is the magnitude of the neutral current?

Three-phase circuits Hard
A. A
B. A
C. A
D. A

57 A balanced positive-sequence source has , , and . If external leads 2 and 3 are interchanged while lead 1 is unchanged, what are the new sequence and the new ?

Numbering and interconnection of three phases Hard
A. Sequence -- and
B. Sequence -- and
C. Sequence -- and
D. Sequence -- and

58 A balanced delta load has branch impedance . For positive sequence, let V. What is line current ?

Delta or mesh connection Hard
A. A
B. A
C. A
D. A

59 A balanced positive-sequence star load has per-phase impedance . If V, what is phase current ?

Relations between line and phase voltages and currents in star networks Hard
A. A
B. A
C. A
D. A

60 In a balanced positive-sequence delta load, the line current is A. What is the branch current ?

Relations between line and phase voltages and currents in delta networks Hard
A. A
B. A
C. A
D. A
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