Basic Electrical Engineering

21. A steady magnetic field can be produced by

  1. a straight wire carrying a constant direct current.
  2. a loop of wire carrying a constant direct current.
  3. a coil of wire carrying a constant direct current.
  4. a constant-intensity stream of protons in free space, moving in a straight line.
  5. any of the above.

Correct answer: (E)
any of the above.

22. A triangular wave exhibits

  1. An instantaneous rise and a defined decay
  2. A defined rise and an instantaneous decay
  3. A defined rise and a defined decay, and the two are equal
  4. An instantaneous rise and an instantaneous decay

Correct answer: (C)
A defined rise and a defined decay, and the two are equal

23. A wave has a frequency of 300kHz. One complete cycle takes…..seconds

  1. 1.3
  2. 0.00333
  3. 401769
  4. 3.33 X 10-6

Correct answer: (D)
3.33 X 10-6

24. A wave has a frequency of 440Hz, how long does it take for 10: of a cycle to occur?

  1. 0.00273s
  2. 0.0000273s
  3. 0.0000631s
  4. 0.00000631s

Correct answer: (C)
0.0000631s

25. An average responding rectifier type electronic ac voltmeter has its scale calibrated in terms of the rms value of a sine wave, when a square wave voltage of peak magnitude 100V is measured using this voltmeter then the reading indicated by the meter, will be ?

  1. 111V
  2. 100V
  3. 90.09V
  4. 70.7V

Correct answer: (B)
100V

26. An inductor works by

  1. Charging a piece of wire
  2. Storing energy as a magnetic field
  3. Choking off dc
  4. Introducing resistance into a field

Correct answer: (B)
Storing energy as a magnetic field

27. Armature reaction in an alternator mainly affects

  1. rotor speed
  2. terminal voltage per phase
  3. frequency of armature current
  4. generated voltage per phase

Correct answer: (D)
generated voltage per phase

28. As capacitor plate area increases

  1. The capacitance increases
  2. The capacitance decreases
  3. The capacitance does not change
  4. The current handling ability decreases

Correct answer: (A)
The capacitance increases

29. As the number of turns in a coil increases, the reactance at a constant frequency

  1. Increases
  2. Decreases
  3. Stays the same
  4. Is stored in the core material

Correct answer: (A)
Increases

30. As the number of turns in a coil that carries ac increases without limit, the current in the coil will

  1. Eventually become very large
  2. Stay the same
  3. Decrease, approaching zero
  4. Be stored in the core material

Correct answer: (C)
Decrease, approaching zero

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