Magnetism and Electromagnetism - MCQ

Magnetism and Electromagnetism - MCQ

4.1. Tesla is a unit of
(a) field strength
(b) inductance
(c) flux density
(d) flux
Ans: c

4.2. A permeable substance is one
(a)     which is a good conductor
(6)     which is a bad conductor
(c) which is a strong magnet
(d) through which the magnetic lines of force can pass very easily
Ans: d

4.3. The materials having low retentivity are suitable for making
(a) weak magnets
(b) temporary magnets
(c) permanent magnets
(d) none of the above
Ans: b

4.4. A magnetic field exists around
(a) iron
(b) copper
(c) aluminium
(d) moving charges
Ans: d

4.7. Ferrites are materials.
(a)     paramagnetic
(b)     diamagnetic
(c) ferromagnetic
(d) none of the above
Ans: c

4.8. Air gap has_______eluctance as compared to iron or steel path
(a) little
(b) lower
(c) higher
(d) zero
Ans: b

4.9. The direction of magnetic lines of force is
(a) from south pole to north pole
(b) from north pole to south pole
(c) from one end of the magnet to another
(d) none of the above
Ans: b

4.10. Which of the following is a vector quantity ?
(a) Relative permeability
(b) Magnetic field intensity
(c) Flux density
(d) Magnetic potential
Ans: b

4.11. The two conductors of a transmission line carry equal current I in opposite directions. The force on each conductor is
(a) proportional to 7
(b) proportional to X
(c) proportional to distance between the conductors
(d) inversely proportional to I
Ans: b

4.12. A material which is slightly repelled by a magnetic field is known as
(a)     ferromagnetic material
(b)     diamagnetic material
(c) paramag>etic material
(d) conducting material
Ans: b

4.13. When an iron piece is placed in a magnetic field
(a)     the magnetic lines of force will bend away from their usual paths in order to go away from the piece
(b)     the magnetic lines of force will bend away from their usual paths in order to pass through the piece
(c) the magnetic field will not be affected
(d) the iron piece will break
Ans: b

4.14. Fleming's left hand rule is used to find
(a) direction of magnetic field due to current carrying conductor
(b) direction of flux in a solenoid
(c) direction of force on a current car¬rying conductor in a magnetic field
(d) polarity of a magnetic pole
Ans: c

4.15. The ratio of intensity of magnetisation to the magnetisation force is known as
(a) flux density
(b) susceptibility
(c) relative permeability
(d) none of the above
Ans: b

4.16. Magnetising steel is normals difficult because
(a)     it corrodes easily
(6)     it has high permeability
(c) it has high specific gravity
(d) it has low permeability
Ans: d

4.17. The left hand rule correlates to
(a) current, induced e.m.f. and direc¬tion of force on a conductor
(b) magnetic field, electric field and direction of force on a conductor
(c) self induction, mutual induction and direction of force on a conductor
(d) current, magnetic field and direc¬tion of force on a conductor
Ans: d

4.18. The unit of relative permeability is
(a)     henry/metre    
(b)     henry
(c) henry/sq. m
(d) it is dimensionless
Ans: d

4.19. 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
(a) zero
(b) BLI
(c) B2LI
(d) BLI2
Ans: a

4.20. The force between two long parallel conductors is inversely proportional to
(a)     radius of conductors
(b)     current in one conductor
(c) product of current in two conduc¬tors
(d) distance between the conductors
Ans: d

4.21. Materials subjected to rapid reversal of magnetism should have
(a) large area oiB-H loop
(b) high permeability and low hysteresis loss
(c) high co-ercivity and high reten-tivity
(d) high co-ercivity and low density
Ans: b

4.22. Indicate which of the following material does not retain magnetism permanently.
(a) Soft iron
(b) Stainless steel
(e) Hardened steel
(d) None of the above
Ans:  : a

4.23. The main constituent of permalloy is
(a) cobalt
(b) chromium
(c) nickel
(d) tungsten
Ans: c

4.24. The use of permanent magnets is. not made in
(a) magnetoes
(6) energy meters
(c) transformers  
(d) loud-speakers
Ans: c

4.25. Paramagnetic materials have relative permeability
(a) slightly less than uuity
(b) equal to unity
(c) slightly more than unity
(d) equal to that ferromagnetic mate rials
Ans: c

4.26. Degaussing is the process of
(a) removal of magnetic impurities
(b) removing gases from the materials
(c) remagnetising metallic parts
(d) demagnetising metallic parts
Ans:

4.27. Substances which have permeability less than the permeability of free space are known as
(a) ferromagnetic
(b) paramagnetic
(c) diamagnetic    
(d) bipolar
Ans: c

4.28. Two infinitely long parallel conductors in vacuum anf' separated 1 metre between centres >rhen a current of 1 ampere flows thn. ugh each conductor, produce on each otLer a force of
(a) 2 x 1(T2 N/m)  
(b) 2 x KT3 N/m
(c) 2 x 10"5 N/m    
(d) 2x 1(T7 N/m)
Ans: d

4.29. In the left hand rule, forefinger always represents
(a)     voltage
(b)     current
(c) magnetic field
(d) direction of force on the conductor
Ans: c

4.30. Which of the following is a ferromagnetic material ?
(a) Tungsten
(b) Aluminium
(c) Copper
(d) Nickel
Ans: d

4.31. Ferrites are a sub-group of
(a)     non-magnetic materials
(6)     ferro-magnetic materials
(c) paramagnetic materials
(d) ferri-magnetic materials
Ans: d

4.32. Gilbert is a unit of
(a) electromotive force
(6) magnetomotive force
(c) conductance    
(d) permittivity
Ans: b

4.33. 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
(a)     meter is surrounded by strong magnetic fields
(b)     a soft iron shielding is used
(c) a plastic shielding is provided
(d) a shielding of anon-magnetic material is used
Ans: b

4.34. Reciprocal of permeability is
(a) reluctivity
(b) susceptibility
(c) permittivity    
(d) conductance
Ans: a

4.35. The relative permeability is less than unity is case of
(a)     ferromagnetic materials
(b)     ferrites
(c) non-ferrous materials
(d) diamagnetic materials
Ans: d

4.36. Which of the following is the unit of magnetic flux density ?
(a)     weber
(b)     lumens
(c) tesla
(d) none of the above
Ans: c

4.37. The magnetism left in the iron after exciting field has been removed is known as
(a) permeance
(b) residual magnetism
(c) susceptance    
(d)     reluctance
Ans: b

4.38. Which of the following is not a unit of flux?
(a) Maxwell
(b) Telsa
(c) Weber
(d) All of the above
Ans: b

4.39. Which of the following is expected to have the maximum permeability ?
(a) Brass
(b) Copper
(c) Zinc
(d) Ebonite
Ans: d

4.40. One telsa is equal to
(a) 1 Wb/mm2
(b) 1 Wb/m
(c) 1 Wb/m2
(d) 1 mWb/m2
Ans: c

4.42. Out of the following statements, concerning an electric field, which statement is not true ?
(a)     The electric intensity is a vector quantity
(b)     The electric field intensity at a point is numerically equal to the force exerted upon a charge placed at that point
(c) An electric field is defined as a point in space at which an electric charge would experienc* a force
(d)     Unit field intensity in the exertion of a force of one newton on a charge of one coulomb
Ans: b

4.43. When a magnet is in motion relative to a coil the induced e.m.f. does not depend upon
(a)     resistance of the coil
(b)     motion of the magnet
(c)    number of turns of the coil
(d) pole strength of the magnet
Ans: a

4.44. One maxwell is equal to
(a) 10  webers    
(b) 10  webers
(c) 10  webers    
(d) 10  webers
Ans: d
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