Quiz  /  Magnetism and Electromagnetism Electrical Engineering MCQ Questions and Answers PDF

  • 1. 
    Tesla is a unit of answer:

  • field strength
  • inductance
  • flux density
  • flux

  • 2. 
    The materials having low retentivity are suitable for making nswer:

  • weak magnets
  • temporary magnets
  • permanent magnets
  • none of the above

  • 3. 
    A magnetic field exists around nswer:

  • iron
  • copper
  • aluminium
  • moving charges

  • 4. 
    Ferrites are materials. nswer:

  • paramagnetic
  • diamagnetic
  • ferromagnetic
  • none of the above

  • 5. 
    Air gap has_______eluctance as compared to iron or steel path nswer:

  • little
  • lower
  • higher
  • zero

  • 6. 
    The direction of magnetic lines of force is nswer:

  • from south pole to north pole
  • from north pole to south pole
  • from one end of the magnet to another
  • none of the above

  • 7. 
    Which of the following is a vector quantity ? nswer:

  • Relative permeability
  • Magnetic field intensity
  • Flux density
  • Magnetic potential

  • 8. 
    The two conductors of a transmission line carry equal current I in opposite directions. The force on each conductor is nswer:

  • proportional to 7
  • proportional to X
  • proportional to distance between the conductors
  • inversely proportional to I

  • 9. 
    A material which is slightly repelled by a magnetic field is known as nswer:

  • ferromagnetic material
  • diamagnetic material
  • paramagnetic material
  • conducting material

  • 10. 
    When an iron piece is placed in a magnetic field nswer:

  • the magnetic lines of force will bend away from their usual paths in order to go away from the piece
  • the magnetic lines of force will bend away from their usual paths in order to pass through the piece
  • the magnetic field will not be affected
  • the iron piece will break

  • 11. 
    Fleming’s left hand rule is used to find nswer:

  • direction of magnetic field due to current carrying conductor
  • direction of flux in a solenoid
  • direction of force on a current carrying conductor in a magnetic field
  • polarity of a magnetic pole

  • 12. 
    The ratio of intensity of magnetisation to the magnetisation force is known as nswer:

  • flux density
  • susceptibility
  • relative permeability
  • none of the above

  • 13. 
    The left hand rule correlates to nswer:

  • current, induced e.m.f. and direction of force on a conductor
  • magnetic field, electric field and direction of force on a conductor
  • self induction, mutual induction and direction of force on a conductor
  • current, magnetic field and direction of force on a conductor

  • 14. 
    The unit of relative permeability is nswer:

  • henry/metre
  • henry
  • henry/sq. m
  • it is dimensionless

  • 15. 
    A conductor of length L has current I passing through it, when it is placed parallel to a magnetic field. The force experienced by the conductor will be nswer:

  • zero
  • BLI
  • B2LI
  • BLI2

  • 16. 
    The force between two long parallel conductors is inversely proportional to nswer:

  • radius of conductors
  • current in one conductor
  • product of current in two conductors
  • distance between the conductors

  • 17. 
    Materials subjected to rapid reversal of magnetism should have nswer:

  • large area oiB-H loop
  • high permeability and low hysteresis loss
  • high co-ercivity and high retentivity
  • high co-ercivity and low density

  • 18. 
    Indicate which of the following material does not retain magnetism permanently. nswer:

  • Soft iron
  • Stainless steel
  • Hardened steel
  • None of the above

  • 19. 
    The main constituent of permalloy is nswer:

  • cobalt
  • chromium
  • nickel
  • tungsten

  • 20. 
    Paramagnetic materials have relative permeability nswer:

  • slightly less than unity
  • equal to unity
  • slightly more than unity
  • equal to that ferromagnetic mate rials

  • 21. 
    Substances which have permeability less than the permeability of free space are known as nswer:

  • ferromagnetic
  • paramagnetic
  • diamagnetic
  • bipolar

  • 22. 
    Two infinitely long parallel conductors in vacuum any separated 1 metre between centers >then a current of 1 ampere flows the. uk each conductor, produce on each other a force of nswer:

  • 2 x 1(T2 N/m)
  • 2 x KT3 N/m
  • 2 x 10″5 N/m
  • 2x 1(T7 N/m)

  • 23. 
    In the left hand rule, forefinger always represents nswer:

  • voltage
  • current
  • magnetic field
  • direction of force on the conductor

  • 24. 
    Which of the following is a ferromagnetic material ? nswer:

  • Tungsten
  • Aluminium
  • Copper
  • Nickel

  • 25. 
    The working of a meter is based on the use of a permanent magnet. In order to protect the meter functioning from stray magnetic fields nswer:

  • meter is surrounded by strong magnetic fields
  • a soft iron shielding is used
  • a plastic shielding is provided
  • a shielding of anon-magnetic material is used

  • 26. 
    Reciprocal of permeability is nswer:

  • reluctivity
  • susceptibility
  • permittivity
  • conductance

  • 27. 
    The relative permeability is less than unity is case of nswer:

  • ferromagnetic materials
  • ferrites
  • non-ferrous materials
  • diamagnetic materials

  • 28. 
    Which of the following is the unit of magnetic flux density ? nswer:

  • weber
  • lumens
  • tesla
  • none of the above

  • 29. 
    The magnetism left in the iron after exciting field has been removed is known as nswer:

  • permeance
  • residual magnetism
  • susceptance
  • reluctance

  • 30. 
    Which of the following is not a unit of flux? nswer:

  • Maxwell
  • Telsa
  • Weber
  • All of the above

  • 31. 
    Which of the following is expected to have the maximum permeability ? nswer:

  • Brass
  • Copper
  • Zinc
  • Ebonite

  • 32. 
    One telsa is equal to nswer:

  • 1 Wb/mm2
  • 1 Wb/m
  • 1 Wb/m2
  • 1 mWb/m2

  • 33. 
    Out of the following statements, concerning an electric field, which statement is not true ? nswer:

  • The electric intensity is a vector quantity
  • The electric field intensity at a point is numerically equal to the force exerted upon a charge placed at that point
  • An electric field is defined as a point in space at which an electric charge would experience a force
  • Unit field intensity in the exertion of a force of one newton on a charge of one coulomb

  • 34. 
    When a magnet is in motion relative to a coil the induced e.m.f. does not depend upon nswer:

  • resistance of the coil
  • motion of the magnet
  • number of turns of the coil
  • pole strength of the magnet

  • 35. 
    One maxwell is equal to nswer:

  • 10 webers
  • 10 webers
  • 10 webers
  • 10 webers

  • 36. 
    When two ends of a circular uniform wire are joined to the terminals of a battery, the field at the center of the circle nswer:

  • will be zero
  • will be infinite
  • will depend on the amount of e.m.f. applied
  • will depend on the radius of the circle

  • 37. 
    Susceptibility is positive for nswer:

  • non-magnetic substances
  • diamagnetic substances
  • ferromagnetic substances
  • none of the above

  • 38. 
    Two long parallel conductors carry 100 A. If the conductors are separated by 20 mm, the force per meter of length of each conductor will be nswer:

  • 100 N
  • 10 N
  • 1 N
  • 0.1 N

  • 39. 
    A 200 turn coil having an axial length of 30 mm and a radius of 10 mm is pivoted in a magnetic field having a flux density of 0.8 T. If the coil carries a current of 0.5 A, the torque acting on the coil will be [Hint. Torque = 2BIlNr N-m] nswer:

  • 8 N-m
  • 0.48 N-m
  • 0.048 N-m
  • 0.0048 N-m

  • 40. 
    The electromagnet has 50 turns and a current of 1A flows through the coil. If the length of the magnet circuit is 200 mm, what is the magnetic field strength ? nswer:

  • 2500 AT/m
  • 250 AT/m
  • 25 AT/m
  • 2.5 AT/m

  • 41. 
    What is the magnitude and the direction of force per 1.1m length of a pair of conductors of a direct current linecarrying 10 amperes and spaced 100 mm apart ? nswer:

  • 22 x 10″8 N
  • 22 x 10″7 N
  • 22 x 10-6 N
  • 22 x 10″5 N

  • 42. 
    A square cross-sectional magnet has a pole strength of 1 x 10 Wb and cross sectional area of 20 mm x 20 mm. What is the strength at a distance of 100 mm from the unit pole in air ? nswer:

  • 63.38 N/Wb
  • 633.8 N/Wb
  • 6338 N/Wb
  • 63380 N/Wb

  • 43. 
    The unit of flux is the same as that of nswer:

  • reluctance
  • resistance
  • permeance
  • pole strength

  • 44. 
    Unit for quantity of electricity is nswer:

  • ampere-hour
  • watt
  • joule
  • coulomb

  • 45. 
    The Biot-savart’s law is a general modification of nswer:

  • Kirchhoffs law
  • Lenz’s law
  • Ampere’s law
  • Faraday’s laws

  • 46. 
    The most effective and quickest may of making a magnet from soft iron is by nswer:

  • placing it inside a coil carrying current
  • induction
  • the use of permanent magnet
  • rubbing with another magnet

  • 47. 
    The commonly used material for shielding or screening magnetism is nswer:

  • copper
  • aluminium
  • soft iron
  • brass

  • 48. 
    If a copper disc is rotated rapidly below a freely suspended magnetic needle, the magnetic needle shall start rotating with a velocity nswer:

  • less than that of disc but in opposite direction
  • equal to that of disc and in the same direction
  • equal to that of disc and in the opposite direction
  • less than that of disc and in the same direction

  • 49. 
    A permanent magnet nswer:

  • attracts some substances and repels others
  • attracts all paramagnetic substances and repels others
  • attracts only ferromagnetic substances
  • attracts ferromagnetic substances and repels all others

  • 50. 
    The retentivity (a property) of material is useful for the construction of nswer:

  • permanent magnets
  • transformers
  • non-magnetic substances
  • electromagnets

  • 51. 
    The relative permeability of materials is not constant. nswer:

  • diamagnetic
  • paramagnetic
  • ferromagnetic
  • insulating

  • 52. 
    The materials are a bit inferior conductors of magnetic flux than air. nswer:

  • ferromagnetic
  • paramagnetic
  • diamagnetic
  • dielectric

  • 53. 
    Hysteresis loop in case of magnetically hard materials is more in shape as compared to magnetically soft materials. nswer:

  • circular
  • triangular
  • rectangular
  • none of the above

  • 54. 
    A keeper is used to nswer:

  • change the direction of magnetic lines
  • amplify flux
  • restore lost flux
  • provide a closed path for flux

  • 55. 
    The change of cross-sectional area of conductor in magnetic field will affect nswer:

  • reluctance of conductor
  • resistance of conductor
  • (a) and (b) both in the same way
  • none of the above

  • 56. 
    The uniform magnetic field is nswer:

  • the field of a set of parallel conductors
  • the field of a single conductor
  • the field in which all lines of magnetic flux are parallel and equidistant
  • none of the above

  • 57. 
    The magneto-motive force is nswer:

  • the voltage across the two ends of exciting coil
  • the flow of an electric current
  • the sum of all currents embraced by one line of magnetic field
  • the passage of magnetic field through an exciting coil

  • 58. 
    What will be the current passing through the ring shaped air cored coil when number of turns is 800 and ampere turns are 3200 ? nswer:

  • 2
  • 4
  • 6
  • 8

  • 59. 
    What will be the magnetic potential difference across the air gap of 2 cm length in magnetic field of 200 AT/m ? nswer:

  • 2 AT
  • 4 AT
  • 6 AT
  • 10 AT

  • 60. 
    A certain amount of current flows through a ring-shaped coil with fixed number of turns. How does the magnetic induction B varies inside the coil if an iron core is threaded into coil without dimensional change of coil ? nswer:

  • Decreases
  • Increases
  • Remains same
  • First increases and then decreases depending on the depth of iron in¬sertion

  • 61. 
    The initial permeability of an iron rod is nswer:

  • the highest permeability of the iron rod
  • the lowest permeability of the iron rod
  • the permeability at the end of the iron rod
  • the permeability almost in non-magnetised state

  • 62. 
    How does the magnetic compass needle behave in a magnetic field ? nswer:

  • It assures a position right angle to magnetic field
  • It starts rotating
  • It assures a position which follows a line of magnetic flux
  • None of the above

  • 63. 
    The stray line of magnetic flux is defined as nswer:

  • a line vertical to the flux lines
  • the mean length of a ring shaped coil
  • a line of magnetic flux in a non-uniform field
  • a line of magnetic flux which does not follow the designed path

  • 64. 
    The bar magnet has nswer:

  • the dipole moment
  • monopole moment
  • (a) and (b) both
  • none of the above

  • 65. 
    Which of the following materials are diamagnetic ? nswer:

  • Silver
  • Copper
  • Silver and copper
  • Iron

  • 66. 
    Which of the following type of materials are not very important for engineering applications ? nswer:

  • Ferromagnetic
  • Paramagnetic
  • Diamagnetic
  • None of the above

  • 67. 
    The susceptibility of paramagnetic materials generally lies between nswer:

  • KT3 and 1CT6
  • 1CT3 and 1CT7
  • KT4 and KT8
  • 10″2 and KT5

  • 68. 
    The magnetic materials exhibit the property of magnetisation because of nswer:

  • orbital motion of electrons
  • spin of electrons
  • spin of nucleus
  • either of these
  • all of the above

  • 69. 
    For which of the following materials the net magnetic moment should be zero ? nswer:

  • Diamagnetic materials
  • Ferrimagnetic materials
  • Antiferromagnetic materials
  • Antiferrimagnetic materials

  • 70. 
    The attraction capacity of electromagnet will increase if the nswer:

  • core length increases i
  • core area increases
  • flux density decreases
  • flux density increases

  • 71. 
    Which of the following statements is correct ? nswer:

  • The conductivity of ferrites is better than ferromagnetic materials
  • The conductivity of ferromagnetic materials is better than ferrites
  • The conductivity of ferrites is very high
  • The conductivity of ferrites is same as that of ferromagnetic materials

  • 72. 
    Temporary magnets are used in nswer:

  • loud-speakers
  • generators
  • motors
  • all of the above

  • 73. 
    Main causes of noisy solenoid are nswer:

  • strong tendency of fan out of laminations at the end caused by repulsion among magnetic lines of force
  • uneven bearing surface, caused by dirt or uneven wear between moving and stationary parts
  • both of above
  • none of the above

  • 74. 
    . Magnetism of a magnet can be destroyed by nswer:

  • heating
  • hammering
  • by inductive action of another magnet
  • by all above methods
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