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AC CIRCUITS > PART 1 > Flashcards

PART 1 Flashcards

1
Q
  1. REE Board Exam September 2000

Find the average current during the half cycle given the instantaneous maximum value of 20 amperes.

A. 12.73 amperes

B. 14.14 amperes

C. 20 amperes

D. 10 amperes

A

Option A

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2
Q
  1. REE Board Exam April 1997

The phase shift between the current and voltage vectors us due to the following except one

A. magnet coils

B. electric flat iron

C. power capacitors

D. fluorescent lamp

A

Option C

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3
Q
  1. REE Board Exam April 2001

An alternating rectangular wave has a maximum value of 10 V and a frequency of 1 cycle per second. What is the average value of the wave?

A. 5 V

B. 10 V

C. 0

D. 7.07 V

A

Option B

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4
Q
  1. REE Board Exam October 2000

A sinusoidal current wave has a maximum value of 20 A. What is the average value of one-half cycle?

A. 5 A

B. 12.7 A

C. 14.14 A

D. 0

A

Option C

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5
Q
  1. REE Board Exam October 1996

What is the wavelength of a carrier wave with frequency of 100 megahertz?

A. 3.0 m

B. 7.5 m

C. 1.5 m

D. 6.0 m

A

Option A

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6
Q
  1. REE Board Exam April 1997

A chart speed of a recording instrument is 25 mm/sec. One cycle of the signal being recorded extends over 5 mm. What is the frequency of the signal?

A. 20 cps

B. 2 cps

C. 50 cps

D. 5 cps

A

Option D

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7
Q
  1. EE Board Exam April 1992

Determine the rms value of the current drawn by a 2 μF condenser, which is connected across a source of potential. The potential has a third and fifth harmonic components, which are 30% and 20% respectively of the fundamental. The fundamental sinusoidal component has a peak value of 1000 volts and 60 Hz frequency.

A. 0.89 A

B. 0.75 A

C. 0.91 A

D. 0.84 A

A

Option A

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8
Q
  1. EE Board Exam April 1990

A 240-V, 25 Hz sinusoidal generator is connected to a 20 ohms resistor. Determine the instantaneous current when elapsed time is 0.01 second.

A. 15.43 A

B. 16.30 A

C. 16.97 A

D. 12.00 A

A

Option C

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9
Q
  1. REE Board Exam April 1997

A wire carries a current i = 3 cos 314t amperes. What is the average current over 6 seconds?

A. 0 A

B. 3.0 A

C. 1.5 A

D. 0.532 A

A

Option A

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10
Q
  1. REE Board Exam April 1997

Across a 230-V, 60 Hz power supply is a 15-ohm non-inductive resistor. What is the equation of the resulting current?

A. i = 21.68 sin 377t

B. i = 26.56 sin 377t

C. i = 15.33 sin 377t

D. i = 28.16 sin 120t

A

Option A

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11
Q
  1. EE Board Exam April 1991

Determine the effective value of the circuit current of an emf of 151 sin 377t is connected in series with a DC emf of 110 volts. Both supply a load of 10 + j8 ohms.

A. 10.3 A

B. 12.5 A

C. 13.8 A

D. 11.4 A

A

Option C

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12
Q
  1. EE Board Exam April 1994

An alternating current and a direct current flow simultaneously in the same conductor. If the effective of the alternating current is 5 A and the direct current is 10 A, what will an AC ammeter read when connected in the circuit?

A. 7.5 A

B. 15 A

C. 11.18 A

D. none of these

A

Option C

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13
Q
  1. REE Board Exam April 1997

If e = 100 sin (ωt – 30°) – 50 cos 3ωt + 25 sin (5ωt + 150°) and i = 20 sin (ωt + 40°) + 10 sin (3ωt + 30°) – 5 sin (5ωt – 50°). Calculate the power in watts.

A. 1177

B. 919

C. 1043

D. 1224

A

Option B

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14
Q
  1. ECE Board Exam November 2001

It is the value of sine wave of voltage or current at one particular instant of time.

A. average value

B. effective value

C. rms value

D. instantaneous value

A

Option D

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15
Q
  1. ECE Board Exam November 1998

If the combination of an ac voltage and a dc voltage has an instantaneous voltage that varies through a range from -2 V to +10 V, what is the peak ac voltage of the combination?

A. 10 V

B. 16 V

C. 6 V

D. 12 V

A

Option D

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16
Q
  1. ECE Board Exam April 2001

Measured in Hertz, it is the number of cycles of alternating current per second.

A. frequency

B. period

C. peak to peak

D. wavelength

A

Option A

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17
Q
  1. ECE Board Exam April 2000

If an ac signal has an average voltage of 18 V, what is the rms voltage?

A. 16.2 V

B. 19.98 V

C. 25.38 V

D. 12.73 V

A

Option B

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18
Q
  1. ECE Board Exam April 2000

If an ac signal has a peak voltage of 55 V, what is the average value voltage?

A. 61.05 V

B. 38.86 V

C. 34.98 V

D. 86.35 V

A

Option C

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19
Q
  1. ECE Board Exam April 1999

What is the phase relationship between current and voltage in an inductor?

A. in phase

B. current lags voltage by 90°

C. voltage lags current by 90°

D. current lags voltage by 180°

A

Option B

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20
Q
  1. ECE Board Exam November 1995

If sine wave voltage varies from 0 to 200 V, how much is its instantaneous voltage at 90°?

A. 100 V

B. minimum voltage

C. 200 V

D. half of its maximum voltage

A

Option C

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21
Q
  1. ECE Board Exam November 2000

How many degrees are there in one complete wave cycle?

A. 360 degrees

B. 90 degrees

C. 180 degrees

D. 720 degrees

A

Option A

22
Q
  1. ECE Board Exam April 1998

When comparing rms voltage and average voltages, which of the following statement is true, assuming sine waves?

A. Either the rms voltage or the average voltage might be larger.

B. The average voltage is always greater than the rms voltage.

C. There will always be a very large difference between the rms voltage and the average voltage.

D. The rms voltage is always greater than the average voltage.

A

D

23
Q
  1. ECE Board Exam November 1999

It is the maximum instantaneous value of a varying current, voltage, or power equal to 1.414 times the effective value of a sine wave.

A. rms value

B. peak to peak value

C. effective value

D. peak value

A

D

24
Q
  1. ECE Board Exam November 1999

It is the description of two sine waves that are in step with each other going through their maximum and minimum points at the same time and in same direction.

A. stepped sine waves

B. sine waves in coordination

C. phased sine waves

D. sine waves in phase

A

Option D

25
Q
  1. ECE Board Exam April 1999

What is the average voltage (Eave) output of a full wave rectifier with an output of 100 volts peak?

A. 63.7 volts

B. 14.14 volts

C. 141.4 volts

D. 6.37 volts

A

Option A

26
Q
  1. ECE Board Exam November 1997

The relation of the voltage across an inductor to it current is _______

A. Lagging the current by 90 degrees

B. Leading the current by 90 degrees

C. In phase with the current

D. Leading the current by 180 degrees

A

Option B

27
Q
  1. ECE Board Exam April 1999

If two equal frequency ac signals of exactly 5 V each are combined with one of the signals 180 degrees out of phase with the other, what will be the value of the resultant voltage?

A. 2.25 V

B. 5 V

C. 0 V

D. 10 V

A

C

28
Q
  1. ECE Board Exam November 1998

Kind of electric current where amplitude drops to zero periodically normally produced by rectifier circuits

A. alternating current

B. varying direct current

C. damped alternating current

D. pulsating direct current

A

D

29
Q
  1. ECE Board Exam April 2000

If an ac signal has an average voltage of 18 V, what is the rms voltage?

A. 16.2 V

B. 19.98 V

C. 25.38 V

D. 12.726 V

A

Option B

30
Q
  1. ECE Board Exam April 2001

In electronic circuit the current that flows over a capacitor _____.

A. In phase with the voltage

B. Leads the voltage by 180 degrees

C. Lags the voltage by 90 degrees

D. Leads the voltage by 90 degrees

A

D

31
Q
  1. Two current sources deliver current to a common load. The first source delivers a current whose equation is 25 sin 100πt amperes while the second delivers a current whose equation is 15 cos 100πt amperes. What is the rms value of the current in the load?

A. 29.15 A

B. 40 A

C. 20.6 A

D. 10 A

A

C

32
Q
  1. Two alternators A and B delivers 100 A and 150 A, respectively to a load. If these currents are out of phase by 30 electrical degrees, determine the total current drawn by the load.

A. 201.5 A

B. 250.0 A

C. 215.4 A

D. 241.8 A

A

D

33
Q
  1. When using circuit laws and rules we must use

A. maximum value

B. average value

C. effective value

D. peak to peak value

A

C

34
Q
  1. A 60 Hz frequency would cause an electric light to

A. turn on and off 120 times per second

B. flicker noticeable

C. turn on and off 180 times per second

D. turn on and off 60 times per second

A

A

35
Q
  1. The relationship between frequency f, number of revolutions per second n and pair of poles p is given by

A. f = n/p

B. f = np

C. f = n/2p

D. f = 2np

A

B

36
Q
  1. The difference between the peak positive value and the peak negative of an a.c. voltage is called the

A. maximum value

B. effective value

C. average value

D. peak to peak value

A

D

37
Q
  1. The greatest value attained during one half of the cycle is called the

A. peak value

B. average value

C. r.m.s. value

D. effective value

A

A

38
Q
  1. The root mean square (r.m.s.) value of a.c. is the same as

A. instantaneous value

B. average value

C. effective value

D. maximum value

A

C

39
Q
  1. The r.m.s. value of a sine wave is equal to

A. 0.637 maximum value

B. 0.506 maximum value

C. 0.707 maximum value

D. 1.414 maximum value

A

C

40
Q
  1. Form factor is defined as

A. r.m.s. value/peak value

B. maximum value/r.m.s. value

C. r.m.s. value/average value

D. effective value/ r.m.s. value

A

C

41
Q
  1. The value of form factor for a pure sine wave is

A. 1.414

B. 0.637

C. 0.707

D. 1.11

A

D

42
Q
  1. The value of peak factor for a pure sine wave is

A. 1.414

B. 0.637

C. 0.707

D. 1.11

A

A

43
Q
  1. If the current and voltage are out of phase by 90°, the power is

A. 1.1 VI

B. minimum

C. Maximum

D. zero

A

D

44
Q
  1. If e1 = A sin ωt and e2 = B sin (ωt – θ) then

A. e1 lags e2 by θ

B. e2 leads e1 by θ

C. e2 lags e1 by θ

D. e1 leads e2 by θ

A

B

45
Q
  1. Which of the following statements concerning the graph of figure below is most correct?

EE Question Banks - img-no.45

A. it represents ac

B. it represents dc

C. it represents half-wave rectified ac

D. it represents sum of ac and dc

A

D

46
Q
  1. Average value of a sine wave is √2 times the maximum value

A. True

B. False

A

B

47
Q
  1. The equation for 25 cycles current sine wave having rms value of 30 amperes will be

A. 30 sin 25t

B. 42.4 sin 25πt

C. 30 sin 50t

D. 42.4 sin 50πt

A

D

48
Q
  1. The voltage v = 90 cos (ωt – 161.5°) may be represented as a sine function by

A. 90 sin (ωt + 18.5°)

B. 90 sin (ωt – 71.5°)

C. 90 sin (ωt + 71.5°)

D. 90 sin (ωt – 18.5°)

A

B

49
Q
  1. Which of the following frequencies has the longest period?

A. 1 Hz

B. 10 Hz

C. 1 kHz

D. 100 kHz

A

A

50
Q
  1. RMS value and the mean value is the same in case of

A. square wave

B. sine wave

C. triangular wave

D. half-wave rectified sine wave

A

A

AC CIRCUITS (2 decks)

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