Electronics And Communications Engineering MCQ

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• Lenz's law is a consequence of the law of conservation of
  ক

  Induced current

  খ

  Charge

  গ

  Energy

  ঘ

  Induced e.m.f.
• A crack in the magnetic path of an inductor will result in
  ক

  Unchanged inductance

  খ

  Increased inductance

  গ

  Zero inductance

  ঘ

  Reduced inductance
• The magnitude of the induced e.m.f. in a conductor depends on the
  ক

  Flux density of the magnetic field

  খ

  Amount of flux cut

  গ

  Amount of flux linkages

  ঘ

  Rate of change of flux-linkages
• The law that the induced e.m.f. and current always oppose the cause producing them is due to
  ক

  Faraday

  খ

  Lenz

  গ

  Newton

  ঘ

  Coulomb
• In case of an inductance, current is proportional to
  ক

  Voltage across the inductance

  খ

  Magnetic field

  গ

  Both A and B

  ঘ

  Neither A nor B
• A laminated iron core has reduced eddy-current losses because
  ক

  More wire can be used with less D.C. resistance in coil

  খ

  The laminations are insulated from each other

  গ

  The magnetic flux is concentrated in the air gap of the core

  ঘ

  The laminations are stacked vertically
• Air-core coils are practically free from
  ক

  Hysteresis losses

  খ

  Eddy current losses

  গ

  Both A and B

  ঘ

  None of the above
• The coefficient of coupling between two air core coils depends on
  ক

  Self-inductance of two coils only

  খ

  Mutual inductance between two coils only

  গ

  Mutual inductance and self inductance of two coils

  ঘ

  None of the above
• As per Faraday's laws of electromagnetic induction, an e.m.f. is induced in a conductor whenever it
  ক

  Lies perpendicular to the magnetic flux

  খ

  Lies in a magnetic field

  গ

  Cuts magnetic flux

  ঘ

  Moves parallel to the direction of the magnetic field
• The self-inductance of the coil may be defined as equal to the e.m.f. induced in volts when the current in the circuit changes at the rate of unit Weber turns.
  ক

  Yes

  খ

  No
• The inductance of a coil will increase under all the following conditions except
  ক

  When more length for the same number of turns is provided

  খ

  When the number of turns of the coil increase

  গ

  When more area for each turn is provided

  ঘ

  When permeability of the core increases
• Higher the self-inductance of a coil,
  ক

  Lesser its weber-turns

  খ

  Lower the e.m.f. induced

  গ

  Greater the flux produced by it

  ঘ

  Longer the delay in establishing steady current through it
• In an iron cored coil the iron core is removed so that the coil becomes an air cored coil. The inductance of the coil will
  ক

  Increase

  খ

  Decrease

  গ

  Remain the same

  ঘ

  Initially increase and then decrease
• Mutually inductance between two magnetically coupled coils depends on
  ক

  Permeability of the core

  খ

  The number of their turns

  গ

  Cross-sectional area of their common core

  ঘ

  All of the above
• A coil is wound on iron core which carries current I. The self-induced voltage in the coil is not affected by
  ক

  Variation in coil current

  খ

  Variation in voltage to the coil

  গ

  Change of number of turns of coil

  ঘ

  The resistance of magnetic path
• If current in a conductor increases then according to Lenz's law self-induced voltage will
  ক

  Aid the increasing current

  খ

  Tend to decrease the amount of current

  গ

  Produce current opposite to the increasing current

  ঘ

  Aid the applied voltage
• The polarity of the induced voltage can be determined by using the left-hand generator rule.
  ক

  Yes

  খ

  No
• Both the number of turns and the core length of an inductive coil are doubled. Its self-inductance will be
  ক

  Unaffected

  খ

  Doubled

  গ

  Halved

  ঘ

  Quadrupled
• Which of the following inductor will have the least eddy current losses?
  ক

  Air core

  খ

  Laminated iron core

  গ

  Iron core

  ঘ

  Powdered iron core
• Which of the following circuit element stores energy in the electromagnetic field?
  ক

  Inductance

  খ

  Condenser

  গ

  Variable resistor

  ঘ

  Resistance
• For a purely inductive circuit which of the following is true?
  ক

  Apparent power is zero

  খ

  Relative power is zero

  গ

  Actual power of the circuit is zero

  ঘ

  Any capacitance even if present in the circuit will not be charged
• Which of the fpllowing inductor will have the least eddy current losses ?
  ক

  Air core

  খ

  Laminated iron core

  গ

  Iron core

  ঘ

  Powdered iron core
• A moving magnetic field will produce the same effect as a conductor that is moving.
  ক

  True

  খ

  False
• Increasing the field or increasing the current will decrease the force on the conductor.
  ক

  Yes

  খ

  No
• The scattering resulting from fiber imperfections like core-cladding RI differences, diameter fluctuations, strains, and bubbles is
  ক

  Rayleigh scattering

  খ

  Mie scattering

  গ

  Stimulated Brillouin scattering

  ঘ

  Stimulated Raman scattering
• Which one of the following statements about differential pulse code modulation (DPCM) is true?
  ক

  The sum of message signal sample with its prediction is quantized

  খ

  The message signal sample is directly quantized, and its prediction is not used

  গ

  The difference of message signal sample and a random signal is quantized

  ঘ

  The difference of message signal sample with its prediction is quantized
• In a broadcast superheterodyne receiver, the
  ক

  Local oscillator operates below the signal frequency

  খ

  Mixer input must be tuned to the signal frequency

  গ

  Local oscillator frequency is normally double the IF

  ঘ

  RF amplifier normally works at 455 kHz above the carrier frequency
• The image frequency of a superheterodyne receiver
  ক

  Is created within the receiver itself

  খ

  Is due to insufficient adjacent channel rejection

  গ

  Is not rejected be the IF tuned circuits

  ঘ

  Is independent of the frequency to which the receiver is tuned
• The frequency generated by each decade in a direct frequency synthesizer is much higher than the frequency shown; this is done to
  ক

  Reduce the spurious frequency problem

  খ

  Increase the frequency stability of the synthesizer

  গ

  Reduce the number of decades

  ঘ

  Reduce the number of crystals required
• One of the main functions of the RF amplifier in a superheterodyne receiver is to
  ক

  Provide improved tracking

  খ

  Permit better adjacent-channel rejection

  গ

  Increase the tuning range of the receiver

  ঘ

  Improve the rejection of the image frequency