Alternating Current Mock Test

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Quiz: Alternating Current – Progressive Test
Total questions: 400
Questions in this round: 50
Time allotted: 70 minutes
Pass score: 60%
Total rounds: 8
Current round: 1^st
Rounds passed: 0 / 8
Weakest rounds: None
Rounds attempted: 0

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Quiz: Alternating Current – Certificate Challenge
Total questions: 400
Questions to attempt: 100 random
Time allotted: 100 minutes
Certificate pass score: 70%
Random questions: Yes
Certificate: Yes
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Progressive Test — Guest First Round

Alternating Current – Progressive Test

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1 / 50

1. Use the graph description below.

For a pure inductor, the instantaneous power-time graph has equal positive and negative regions over one complete cycle.

The physical meaning of this graph is that

a) the current remains zero during the whole cycle

b) energy is stored and later returned

c) the voltage and current are in phase

d) the inductor permanently dissipates all supplied energy

2 / 50

2. A choke coil used in an circuit should ideally have

a) zero inductance and high resistance

b) low inductance and high resistance

c) high inductance and low resistance

d) high capacitance and no magnetic core

3 / 50

3. Flux leakage in a transformer means that

a) some primary flux does not link the secondary coil

b) the number of turns in both coils becomes zero

c) the secondary current becomes

d) all magnetic flux produced by the primary links the secondary perfectly

4 / 50

4. An source is connected to a series circuit with , , and . The peak current is closest to

5 / 50

5. A rms source supplies a series circuit. At one frequency, and . The power factor is

6 / 50

6. The opposite directions of and in a series phasor diagram occur because

a) leads current and lags current

b) the inductor and capacitor always have equal voltages

c) the same current cannot pass through both and

d) the resistor voltage cancels both of them

7 / 50

7. The opposition offered by an ideal inductor to sinusoidal is called

a) inductive reactance

b) capacitive reactance

c) conductance

d) resistance

8 / 50

8. Use the graph description below.

Two sinusoidal graphs have the same time period. Graph P crosses zero with positive slope at . Graph Q crosses zero with positive slope at a later time.

The suitable conclusion is that

a) the two graphs must have different frequencies

b) Graph Q leads graph P

c) Graph Q lags graph P

d) the two graphs must have zero amplitude

9 / 50

9. A series circuit behaves capacitively when the inductive reactance is negligible. It has , , and angular frequency . The power factor magnitude is

10 / 50

10. Near resonance in a series circuit, high voltages may appear across and even when the source voltage is modest. The safest interpretation is that

a) and are large but nearly opposite in phase

b) the resistor voltage is always greater than both and

c) the current through and must be zero

d) Kirchhoff’s voltage law fails in

11 / 50

11. A circuit element has current leading voltage by and its reactance decreases when frequency increases. The element is most suitably identified as

a) pure capacitor

b) pure resistor

c) pure inductor

d) ideal resistor with variable resistance

12 / 50

12. A claim says: “If and , the source must supply at least .” The claim is unsuitable because

a) inductor voltage is not measured in volts

b) capacitor voltage is always zero in

c) and are in opposite phasor directions

d) series current cannot pass through a capacitor

13 / 50

13. A waveform is described by the readings , , , , and in sequence over one cycle. The value that changes from instant to instant is

14 / 50

14. Study the table and identify the suitable row for a pure inductive circuit.

Row	Feature	Pure inductor result
P	Phase relation	Current lags voltage by
Q	Reactance
R	Frequency effect	decreases as increases
S	Average power	Always equal to

a) Row R

b) Row Q

c) Row S

d) Row P

15 / 50

15. When in a series circuit and , the source voltage at that frequency is

16 / 50

16. A series circuit has , while the source voltage is only . This is possible because

a) voltage across each element must always be less than the source voltage

b) the resistor voltage must be zero in every series circuit

c) current is different in and

d) and are opposite phasors and can cancel in the resultant

17 / 50

17. A power station transmits at . Ignoring phase complications, the transmission current is

18 / 50

18. In , the argument must represent an angle. This is consistent because

a) is a current and must be measured in

b) both and are measured in

c) has unit and has unit

d) has unit

19 / 50

19. A sinusoidal current has . The peak current and peak-to-peak current are respectively

a) and

b) and

c) and

d) and

20 / 50

20. With , , and in a series circuit, the source voltage is closest to

21 / 50

21. Study the table and identify the row that correctly represents power in a series circuit.

Row	Quantity	Suitable expression
P	Average power
Q	Power factor
R	Real power
S	Apparent power

a) Row Q

b) Row P

c) Row S

d) Row R

22 / 50

22. If the resistance of a series circuit is increased while , , and the resonant frequency remain fixed, the resonance curve becomes

a) broader and less selective

b) a straight line through the origin

c) sharper and narrower

d) unchanged in width

23 / 50

23. A series circuit has , , and . Its quality factor is

24 / 50

24. A series resonant circuit has and bandwidth . Its quality factor is

25 / 50

25. A sinusoidal current has . Its rms current is approximately

26 / 50

26. A resonance curve for a series circuit plots on the vertical axis and frequency on the horizontal axis. The peak of the curve occurs at

a) every frequency equally

b) always

27 / 50

27. In a series circuit with , , and , the value of is

28 / 50

28. Study the table and identify the row with suitable transformer notation.

Row	Symbol	Meaning
P		Number of turns in the primary coil
Q		Primary current
R		Secondary voltage
S		Number of turns in the secondary coil

a) Row R

b) Row Q

c) Row S

d) Row P

29 / 50

29. A capacitor blocks steady after it becomes fully charged, but an alternating current can exist in the external circuit connected to it because

a) the capacitance becomes zero in every half cycle

b) the applied voltage keeps the capacitor charging and discharging

c) charge stops appearing on the capacitor plates

d) the applied voltage removes the dielectric completely

30 / 50

30. A choke coil of inductance and negligible resistance is connected to a , supply. Taking , the rms current is approximately

31 / 50

31. The same power is transmitted through wires of resistance first at voltage and then at voltage . If power factor effects are ignored, the line loss in the second case becomes

a) times the first loss

b) times the first loss

c) of the first loss

d) of the first loss

32 / 50

32. A soft iron core is preferred in a transformer because it

a) prevents any magnetic flux from linking the secondary

b) has high hysteresis loss and poor magnetic response

c) makes the transformer suitable for steady only

d) reduces hysteresis loss and improves magnetic coupling

33 / 50

33. The notation is used instead of in an equation when the voltage value is meant to be

a) instantaneous voltage

b) the number of cycles per second

c) the time period of the supply

d) the maximum voltage only

34 / 50

34. Use the graph description below.

Graph P shows and reaching maxima together. Graph Q shows reaching maximum one quarter cycle before . Graph R shows reaching maximum one quarter cycle before .

The suitable identification of P, Q, and R is

a) P: pure , Q: pure , R: pure

b) P: pure , Q: pure , R: pure

c) P: pure , Q: pure , R: pure

d) P: pure , Q: pure , R: pure

35 / 50

35. In a series circuit, , net reactance , and . The reactive voltage magnitude is

36 / 50

36. Series resonance in an circuit occurs when

37 / 50

37. A series circuit has maximum current at resonance. At a half-power frequency, the current is closest to

38 / 50

38. A series circuit has , , , and . At , the rms current and circuit nature are closest to

a) , capacitive

b) , capacitive

c) , inductive

d) , inductive

39 / 50

39. The instantaneous power in an circuit is always defined as

40 / 50

40. The SI unit of inductive reactance is

41 / 50

41. The phase relation “current lags voltage by ” belongs to

a) a source with zero frequency only

b) a pure resistor

c) a pure inductor

d) a pure capacitor

42 / 50

42. A source is described by the values , , , and . The pair that contains one amplitude quantity and one phase-related quantity is

a) and

b) and

d) and

43 / 50

43. A pure capacitor has and . The peak current and phase relation are

a) , current lags voltage by

b) , voltage leads current by

c) , current leads voltage by

d) , current leads voltage by

44 / 50

44. In the beginning of circuit analysis, a sinusoidal variation is preferred because it represents

a) a current that increases forever with time

b) a random change with no fixed repetition

c) a smooth repeating sinusoidal change

d) a voltage that must remain positive at all instants

45 / 50

45. Two sinusoidal currents are represented by and . The two currents have the same

a) peak value only

b) instantaneous value at every instant only

c) angular frequency and phase pattern

d) unit of voltage

46 / 50

46. A pure resistor of resistance is connected to an source with . The peak current is

47 / 50

47. A sinusoidal current is represented by . At , the current is

48 / 50

48. In an circuit, the instantaneous voltage and current at a certain instant are and . The instantaneous power at that instant is

49 / 50

49. A real coil has small resistance along with inductance, while an ideal pure inductor has only inductance. The average power is exactly zero only for

a) the ideal pure inductor, because it has no resistive loss

b) both coils, regardless of resistance

c) the real coil, because every coil has inductance

d) neither, because all circuits consume zero power

50 / 50

50. A transformer delivers at to a load and has efficiency . If the primary voltage is , the primary current is

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Alternating Current Mock Test – Class 12 Physics

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