A.C Fundamentals MCQ

Test your knowledge with important A.C Fundamentals MCQ and their applications. These MCQs are beneficial for competitive exams too. Explore 30 + more A.C Fundamentals MCQs at Bissoy

• The frequency of an alternating current is
  ক

  The speed with which the alternator runs

  খ

  The number of cycles generated in one minute

  গ

  The number of waves passing through a point in one second

  ঘ

  The number of electrons passing through a point in one second
• All definitions of power factor of a series R-L-C circuit are correct except
  ক

  Ratio of net reactance and impedance

  খ

  Ratio of kW and kVA

  গ

  Ratio of J and Z

  ঘ

  Ratio of W and VA
• The best place to install a capacitor is
  ক

  Very near to inductive load

  খ

  Across the terminals of the inductive load

  গ

  Far away from the inductive load

  ঘ

  Any where
• In a circuit containing R, L and C, power loss can take place in
  ক

  C only

  খ

  L only

  গ

  R only

  ঘ

  All above
• In a series L-C circuit at the resonant frequency the
  ক

  Current is maximum

  খ

  Current is minimum

  গ

  Impedance is maximum

  ঘ

  Voltage across C is minimum
• Which of the following statements pertains to resistors only?
  ক

  Can dissipate considerable amount of power

  খ

  Can act as energy storage devices

  গ

  Connecting them in parallel increases the total value

  ঘ

  Oppose sudden changes in voltage
• The power consumed in a circuit element will be least when the phase difference between the current and voltage is
  ক

  180°

  খ

  90°

  গ

  60°

  ঘ

  0°
• Capacitors for power factor correction are rated in
  ক

  kW

  খ

  kVA

  গ

  kV

  ঘ

  kVAR
• In a pure resistive circuit
  ক

  Current lags behind the voltage by 90°

  খ

  Current leads the voltage by 90°

  গ

  Current can lead or lag the voltage by 90°

  ঘ

  Current is in phase with the voltage
• In a pure inductive circuit
  ক

  The current is in phase with the voltage

  খ

  The current lags behind the voltage by 90°

  গ

  The current leads the voltage by 90°

  ঘ

  The current can lead or lag by 90°
• Pure inductive circuit
  ক

  Consumes some power on average

  খ

  Does not take power at all from a line

  গ

  Takes power from the line during some part of the cycle and then returns back to it during other part of the cycle

  ঘ

  None of the above
• The frequency of domestic power supply in India is
  ক

  200 Hz

  খ

  100 Hz

  গ

  60 Hz

  ঘ

  50 Hz
• Form factor for a sine wave is
  ক

  1.414

  খ

  0.707

  গ

  1.11

  ঘ

  0.637
• Poor power factor
  ক

  Reduces load handling capability of electrical system

  খ

  Results in more power losses in the electrical system

  গ

  Overloads alternators, transformers and distribution lines

  ঘ

  Results in all above
• An A.C. voltage is impressed across a pure resistance of 3.5 ohms in parallel with a pure inductance of impedance of 3.5 ohms,
  ক

  The current through the resistance is more

  খ

  The current through the resistance is less

  গ

  Both resistance and inductance carry equal currents

  ঘ

  None of the above
• In a highly capacitive circuit the
  ক

  Apparent power is equal to the actual power

  খ

  Reactive power is more than the apparent power

  গ

  Reactive power is more than the actual power

  ঘ

  Actual power is more than its reactive power
• The safest value of current the human body can carry for more than 3 second is
  ক

  4 mA

  খ

  9 mA

  গ

  15 mA

  ঘ

  25 mA
• The purpose of a parallel circuit resonance is to magnify
  ক

  Current

  খ

  Voltage

  গ

  Power

  ঘ

  Frequency
• The r.m.s. value of a sinusoidal A.C. current is equal to its value at an angle of ________ degrees.
  ক

  90

  খ

  60

  গ

  45

  ঘ

  30
• When an alternating current passes through an ohmic resistance the electrical power converted into heat is
  ক

  Apparent power

  খ

  True power

  গ

  Reactive power

  ঘ

  None of the above
• Two waves of the same frequency have opposite phase when the phase angle between them is
  ক

  360°

  খ

  180°

  গ

  90°

  ঘ

  0°
• Inductance of a coil Varies
  ক

  Directly as the cross-sectional area of magnetic core

  খ

  Directly as square of number of turns

  গ

  Inversely as the length of the iron path

  ঘ

  All of above
• Magnitude of current at resonance in R-L-C circuit
  ক

  Depends upon the magnitude of R

  খ

  Depends upon the magnitude of L

  গ

  Depends upon the magnitude of C

  ঘ

  Depends upon the magnitude of R, Land C
• Time constant of a circuit is the time in seconds taken after the application of voltage to each
  ক

  25% of maximum value

  খ

  50% of maximum value

  গ

  63% of maximum value

  ঘ

  90% of the maximum value
• The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 ohms. If frequency is increased to 100 Hz, reactance becomes __________ ohms.
  ক

  2.5

  খ

  5

  গ

  10

  ঘ

  15
• Pure inductive circuit takes power from the A.C. line when
  ক

  Applied voltage decreases but current increases

  খ

  Applied voltage increases but current decreases

  গ

  Both applied voltage and current increase

  ঘ

  Both applied voltage and current decrease
• In a purely inductive circuit
  ক

  Actual power is zero

  খ

  Reactive power is zero

  গ

  Apparent power is zero

  ঘ

  None of above is zero
• Which of the following waves has the highest value of peak factor ?
  ক

  Square wave

  খ

  Sine wave

  গ

  Half wave rectified sine wave

  ঘ

  Triangular wave
• The product of apparent power and cosine of the phase angle between circuit voltage and current is
  ক

  True power

  খ

  Reactive power

  গ

  Volt-amperes

  ঘ

  Instantaneous power
• The peak value of a sine wave is 200 V. Its average value is
  ক

  127.4 V

  খ

  141.4 V

  গ

  282.8 V

  ঘ

  200 V