McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
Chapters
| 51. |
The most effective and quickest may of making a magnet from soft iron is by |
| A. | placing it inside a coil carrying current |
| B. | induction |
| C. | the use of permanent magnet |
| D. | rubbing with another magnet |
| Answer» A. placing it inside a coil carrying current | |
| 52. |
The commonly used material for shielding or screening magnetism is |
| A. | copper |
| B. | aluminium |
| C. | soft iron |
| D. | brass |
| Answer» C. soft iron | |
| 53. |
If a copper disc is rotated rapidly below a freely suspended magnetic needle, the magnetic needle shall start rotating with a velocity |
| A. | less than that of disc but in opposite direction |
| B. | equal to that of disc and in the same direction |
| C. | equal to that of disc and in the opposite direction |
| D. | less than that of disc and in the same direction |
| Answer» D. less than that of disc and in the same direction | |
| 54. |
A permanent magnet |
| A. | attracts some substances and repels others |
| B. | attracts all paramagnetic substan¬ces and repels others |
| C. | attracts only ferromagnetic sub¬stances |
| D. | attracts ferromagnetic substances and repels all others |
| Answer» A. attracts some substances and repels others | |
| 55. |
The retentivity (a property) of material is useful for the construction of |
| A. | permanent magnets |
| B. | transformers |
| C. | non-magnetic substances |
| D. | electromagnets |
| Answer» A. permanent magnets | |
| 56. |
The relative permeability of materials is not constant. |
| A. | diamagnetic |
| B. | paramagnetic |
| C. | ferromagnetic |
| D. | insulating |
| Answer» C. ferromagnetic | |
| 57. |
The materials are a bit inferior conductors of magnetic flux than air. |
| A. | ferromagnetic |
| B. | paramagnetic |
| C. | diamagnetic |
| D. | dielectric |
| Answer» C. diamagnetic | |
| 58. |
Hysteresis loop in case of magnetically hard materials is more in shape as compared to magnetically soft materials. |
| A. | circular |
| B. | triangular |
| C. | rectangular |
| D. | none of the above |
| Answer» C. rectangular | |
| 59. |
A rectangular magnet of magnetic moment M is cut into two piece of same length, the magnetic moment of each piece will be |
| A. | M |
| B. | M/2 |
| C. | 2 M |
| D. | M/4 |
| Answer» B. M/2 | |
| 60. |
A keeper is used to |
| A. | change the direction of magnetic lines |
| B. | amplify flux |
| C. | restore lost flux |
| D. | provide a closed path for flux |
| Answer» D. provide a closed path for flux | |
| 61. |
Magnetic moment is a |
| A. | pole strength |
| B. | universal constant |
| C. | scalar quantity |
| D. | vector quantity |
| Answer» D. vector quantity | |
| 62. |
The change of cross-sectional area of conductor in magnetic field will affect |
| A. | reluctance of conductor |
| B. | resistance of conductor |
| C. | (a) and (b) b >th in the same way |
| D. | none of the above |
| Answer» C. (a) and (b) b >th in the same way | |
| 63. |
The uniform magnetic field is |
| A. | the field of a set of parallel conductors |
| B. | the field of a single conductor |
| C. | the field in which all lines of mag¬netic flux are parallel and equidis¬tant |
| D. | none of the above |
| Answer» C. the field in which all lines of mag¬netic flux are parallel and equidis¬tant | |
| 64. |
The magneto-motive force is |
| A. | the voltage across the two ends of exciting coil |
| B. | the flow of an electric current |
| C. | the sum of all currents embraced by one line of magnetic field |
| D. | the passage of magnetic field through an exciting coil |
| Answer» C. the sum of all currents embraced by one line of magnetic field | |
| 65. |
What will be the current passing through the ring shaped air cored coil when number of turns is 800 and ampere turns are 3200 ? |
| A. | 2 |
| B. | 4 |
| C. | 6 |
| D. | 8 |
| Answer» B. 4 | |
| 66. |
What will be the magnetic potential difference across the air gap of 2 cm length in magnetic field of 200 AT/m ? |
| A. | 2 AT |
| B. | 4 AT |
| C. | 6 AT |
| D. | 10 AT |
| Answer» B. 4 AT | |
| 67. |
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 ? |
| A. | Decreases |
| B. | Increases |
| C. | Remains same |
| D. | First increases and then decreases depending on the depth of iron in¬sertion |
| Answer» B. Increases | |
| 68. |
The magnetic reluctance of a material |
| A. | decreases with increasing cross sectional area of material |
| B. | increases with increasing cross-sec-tional area of material |
| C. | does not vary with increasing cross-sectional area of material |
| D. | any of the above |
| Answer» A. decreases with increasing cross sectional area of material | |
| 69. |
The initial permeability of an iron rod is |
| A. | the highest permeability of the iron rod |
| B. | the lowest permeability of the iron rod |
| C. | the permeability at the end of the iron rod |
| D. | the permeability almost in non-magnetised state |
| Answer» D. the permeability almost in non-magnetised state | |
| 70. |
How does the magnetic compass needle behave in a magnetic field ? |
| A. | It assures a position right angle to magnetic field |
| B. | It starts rotating |
| C. | It assures a position which follows a line of magnetic flux |
| D. | None of the above |
| Answer» C. It assures a position which follows a line of magnetic flux | |
| 71. |
In a simple magnetic field the strength of magnet flux |
| A. | is constant and has same value in energy part of the magnetic field |
| B. | increases continuously from initial value to final value |
| C. | decreases continuously from initial value to final value |
| D. | first increases and then decreases till it becomes zero |
| Answer» D. first increases and then decreases till it becomes zero | |
| 72. |
The stray line of magnetic flux is defined as |
| A. | a line vertical to the flux lines |
| B. | the mean length of a ring shaped coil |
| C. | a line of magnetic flux in a non-uniform field |
| D. | a line of magnetic flux which does not follow the designed path |
| Answer» D. a line of magnetic flux which does not follow the designed path | |
| 73. |
The bar magnet has |
| A. | the dipole moment |
| B. | monopole moment |
| C. | (a) and (b) both |
| D. | none of the above |
| Answer» A. the dipole moment | |
| 74. |
Which of the following materials are dia-magnetic ? |
| A. | Silver |
| B. | Copper |
| C. | Silver and copper |
| D. | Iron |
| Answer» C. Silver and copper | |
| 75. |
Which of the following type of materials are not very important for engineering applications ? |
| A. | Ferromagnetic |
| B. | Paramagnetic |
| C. | Diamagnetic |
| D. | None of the above |
| Answer» C. Diamagnetic | |
| 76. |
The susceptibility of paramagnetic materials generally lies between |
| A. | KT3 and 1CT6 |
| B. | 1CT3 and 1CT7 |
| C. | KT4 and KT8 |
| D. | 10"2 and KT5 |
| Answer» A. KT3 and 1CT6 | |
| 77. |
For which of the following materials the saturation value is the highest ? |
| A. | Ferromagnetic materials |
| B. | Paramagnetic materials |
| C. | Diamagnetic materials |
| D. | Ferrites |
| Answer» D. Ferrites | |
| 78. |
The magnetic materials exhibit the property of magnetisation because of |
| A. | orbital motion of electrons |
| B. | spin of electrons |
| C. | spin of nucleus |
| D. | either of these |
| Answer» C. spin of nucleus | |
| 79. |
For which of the following materials the net magnetic moment should be zero ? |
| A. | Diamagnetic materials |
| B. | Ferrimagnetic materials |
| C. | Antiferromagnetic materials |
| D. | Antiferrimagnetic materials |
| Answer» C. Antiferromagnetic materials | |
| 80. |
The attraction capacity of electromagnet will increase if the |
| A. | core length increases i |
| B. | core area increases |
| C. | flux density decreases |
| D. | flux density increases |
| Answer» D. flux density increases | |
| 81. |
Which of the following statements is correct ? |
| A. | The conductivity of ferrites is better than ferromagnetic materials |
| B. | The conductivity of ferromagnetic materials is better than ferrites |
| C. | The conductivity of ferrites is very high |
| D. | The conductivity of ferrites is same as that of ferromagnetic materials |
| Answer» A. The conductivity of ferrites is better than ferromagnetic materials | |
| 82. |
Temporary magnets are used in |
| A. | loud-speakers |
| B. | generators |
| C. | motors |
| D. | all of the above |
| Answer» D. all of the above | |
| 83. |
Main causes of noisy solenoid are |
| A. | strong tendency of fan out of lami-nations at the end caused by repul¬sion among magnetic lines of force |
| B. | uneven bearing surface, caused by dirt or uneven wear between moving and stationary parts |
| C. | both of above |
| D. | none of the above |
| Answer» C. both of above | |
| 84. |
Core of an electromagnet should have |
| A. | low coercivity |
| B. | high susceptibility |
| C. | both of the above |
| D. | none of the above |
| Answer» C. both of the above | |
| 85. |
Magnetism of a magnet can be destroyed by |
| A. | heating |
| B. | hammering |
| C. | by inductive action of another magnet |
| D. | by all above methods |
| Answer» D. by all above methods | |
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