Electromagnetic Induction 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
• A conductor carries 125 amperes of current under 60° to a magnetic field of 1.1 tesla. The force on the conductor will be nearly
  ক

  50 N

  খ

  120 N

  গ

  240 N

  ঘ

  480 N
• 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
• An average voltage of 10 V is induced in a 250 turns solenoid as a result of a change in flux which occurs in 0.5 second. The total flux change is
  ক

  20 Wb

  খ

  2 Wb

  গ

  0.2 Wb

  ঘ

  0.02 Wb
• 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
• A coil induces 350 mV when the current changes at the rate of 1 A/s. The value of inductance is
  ক

  3500 mH

  খ

  350 mH

  গ

  250 mH

  ঘ

  150 mH
• Current changing from 8 A to 12 A in one second induced 20 volts in a coil. The value of inductance is
  ক

  5 mH

  খ

  10 mH

  গ

  5 H

  ঘ

  10 H
• 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
• Two coils have self-inductances of 10 H and 2 H, the mutual inductance being zero. If the two coils are connected in series, the total inductance will be
  ক

  6 H

  খ

  8 H

  গ

  12 H

  ঘ

  24 H
• Two coils have inductances of 8 mH and 18 mH and a coefficient of coupling of 0.5. If the two coils are connected in series aiding, the total inductance will be
  ক

  32 mH

  খ

  38 mH

  গ

  40 mH

  ঘ

  48 mH
• 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
• A conductor 2 meters long moves at right angles to a magnetic field of flux density 1 tesla with a velocity of 12.5 m/s. The induced e.m.f. in the conductor will be
  ক

  10 V

  খ

  15 V

  গ

  25 V

  ঘ

  50 V
• 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
• Find the force acting on a conductor 3m long carrying a current of 50 amperes at right angles to a magnetic field having a flux density of 0.67 tesla
  ক

  100 N

  খ

  400 N

  গ

  600 N

  ঘ

  1000 N
• 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
• An e.m.f. of 16 volts is induced in a coil of inductance 4H. The rate of change of current must be
  ক

  64 A/s

  খ

  32 A/s

  গ

  16 A/s

  ঘ

  4 A/s
• A 200 turn coil has an inductance of 12 mH. If the number of turns is increased to 400 turns, all other quantities (area, length etc.) remaining the same, the inductance will be
  ক

  6 mH

  খ

  146 mH

  গ

  24 mH

  ঘ

  48 mH