MCQOPTIONS
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MCQOPTIONS
This section includes 110 Mcqs, each offering curated multiple-choice questions to sharpen your Electronics knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
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] |
| A. | 8 N-m |
| B. | 0.48 N-m |
| C. | 0.048 N-m |
| D. | 0.0048 N-m |
| Answer» D. 0.0048 N-m | |
| 52. |
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» E. | |
| 53. |
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? |
| A. | 2500 AT/m |
| B. | 250 AT/m |
| C. | 25 AT/m |
| D. | 2.5 AT/m |
| Answer» C. 25 AT/m | |
| 54. |
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 experience a force |
| D. | Unit field intensity in the exertion of a force of one newton on a charge of one coulomb |
| Answer» C. An electric field is defined as a point in space at which an electric charge would experience a force | |
| 55. |
Core of an electromagnet should have |
| A. | low coercivity |
| B. | high susceptibility |
| C. | both of the above |
| D. | none of the above |
| Answer» D. none of the above | |
| 56. |
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 ? |
| A. | 22 x 10"8 N |
| B. | 22 x 10"7 N |
| C. | 22 x 10-6 N |
| D. | 22 x 10"5 N |
| Answer» E. | |
| 57. |
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 |
| Answer» C. proportional to distance between the conductors | |
| 58. |
Which of the following is a ferromagnetic material? |
| A. | Tungsten |
| B. | Aluminium |
| C. | Copper |
| D. | Nickel |
| Answer» E. | |
| 59. |
Air gap has_______eluctance as compared to iron or steel path |
| A. | little |
| B. | lower |
| C. | higher |
| D. | zero |
| Answer» C. higher | |
| 60. |
Degaussing is the process of |
| A. | removal of magnetic impurities |
| B. | removing gases from the materials |
| C. | remagnetising metallic parts |
| D. | demagnetising metallic parts |
| Answer» E. | |
| 61. |
The use of permanent magnets is. not made in |
| A. | magnetoes |
| B. | energy meters |
| C. | transformers |
| D. | loud-speakers |
| Answer» D. loud-speakers | |
| 62. |
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» C. Remains same | |
| 63. |
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» D. None of the above | |
| 64. |
Magnetic moment is a |
| A. | pole strength |
| B. | universal constant |
| C. | scalar quantity |
| D. | vector quantity |
| Answer» E. | |
| 65. |
For which of the following materials the saturation value is the highest? |
| A. | Ferromagnetic materials |
| B. | Paramagnetic materials |
| C. | Diamagnetic materials |
| D. | Ferrites |
| Answer» E. | |
| 66. |
Magnetising steel is normals difficult because |
| A. | it corrodes easily |
| B. | it has high permeability |
| C. | it has high specific gravity |
| D. | it has low permeability |
| Answer» E. | |
| 67. |
Which of the following materials are diamagnetic? |
| A. | Silver |
| B. | Copper |
| C. | Silver and copper |
| D. | Iron |
| Answer» D. Iron | |
| 68. |
A 300 mm long conductor is carrying a current of 10 A and is situated at right angles to a magnetic field having a flux density of 0.8 T ; the force on the conductor will be |
| A. | 240 N |
| B. | 24 N |
| C. | 2.4 N |
| D. | 0.24 N |
| Answer» D. 0.24 N | |
| 69. |
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 |
| Answer» B. BLI | |
| 70. |
The magnetomotive 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» D. the passage of magnetic field through an exciting coil | |
| 71. |
Indicate which of the following material does not retain magnetism permanently. |
| A. | Soft iron |
| B. | Stainless steel |
| C. | Hardened steel |
| D. | None of the above |
| Answer» B. Stainless steel | |
| 72. |
Which of the following is the unit of magnetic flux density? |
| A. | Weber |
| B. | Lumens |
| C. | Tesla |
| D. | None of the above |
| Answer» D. None of the above | |
| 73. |
What is the magneto-motive force in a 75-turn coil of wire when there are 4 A of current through it? |
| A. | 18.75 At |
| B. | 30 At |
| C. | 300 At |
| D. | 187 At |
| Answer» D. 187 At | |
| 74. |
Strength of an electromagnet can be increased by |
| A. | increasing the cross-sectional area |
| B. | increasing the number of turns |
| C. | increasing current supply |
| D. | all above methods |
| Answer» E. | |
| 75. |
What is the magneto-motive force (mmf) of a wire with 8 turns carrying three amperes of current? |
| A. | 2,400 At |
| B. | 240 At |
| C. | 24 At |
| D. | 2.4 At |
| Answer» D. 2.4 At | |
| 76. |
___ is the ability of a material to remain magnetized after removal of the magnetizing force. |
| A. | Reluctance |
| B. | Hysteresis |
| C. | Retentivity |
| D. | Induction |
| Answer» D. Induction | |
| 77. |
The ___ is an electromagnetic device that contains a coil rotating on a jeweled bearing mount. |
| A. | permanent-magnet speaker |
| B. | d'Arsonval movement |
| C. | single-pole, double-throw relay |
| D. | crankshaft position sensor |
| Answer» C. single-pole, double-throw relay | |
| 78. |
When the south poles of two bar magnets are brought close together, there will be a force of attraction. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 79. |
The operation of an electrical generator relies on electromagnetic induction. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 80. |
The magnetic field, current through the Hall element, and Hall voltage are all at right angles to each other. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 81. |
A voltage is induced across a conductor if it remains absolutely stationary within a magnetic field. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 82. |
When the speed at which a conductor is moved through a magnetic field is increased, the induced voltage will _____. |
| A. | not be affected |
| B. | equal 0 V |
| C. | decrease |
| D. | increase |
| Answer» E. | |
| 83. |
A magnetic field is produced around a current-carrying conductor. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 84. |
The unit of magnetic flux is the weber. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 85. |
Ferromagnetic materials have minute magnetic ___ created within their atomic structure by the orbital motion and spin of electrons. |
| A. | forces |
| B. | flux lines |
| C. | domains |
| D. | tapes |
| Answer» D. tapes | |
| 86. |
The induced emf of a conductor cutting flux lines is directly proportional to the rate of cutting. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 87. |
The induced voltage across a stationary conductor in a stationary magnetic field ___. |
| A. | equals 0 V |
| B. | is usually very large |
| C. | varies with time |
| D. | depends on the strength of the magnetic field |
| Answer» B. is usually very large | |
| 88. |
Magnetic flux flows from the north pole to the south pole within the magnet. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 89. |
"Series" and "parallel" as applied to dc motors refer to |
| A. | the connection of the motor and controller |
| B. | the connection of the field coil and armature windings |
| C. | the connection of the brush and commutator |
| D. | the connection of the motor batteries |
| Answer» C. the connection of the brush and commutator | |
| 90. |
Which electromagnetic device has a flexible cone? |
| A. | A speaker |
| B. | A dc generator |
| C. | A relay |
| D. | A solenoid |
| Answer» B. A dc generator | |
| 91. |
The unit of flux density is known as |
| A. | magnetomotive force |
| B. | a weber |
| C. | a maxwell |
| D. | a tesla |
| Answer» E. | |
| 92. |
A magnetic material such as iron can change the course of magnetic lines of force. |
| A. | 1 |
| B. | |
| C. | 1 |
| D. | |
| Answer» B. | |
| 93. |
You can determine the direction of the lines of force surrounding a conductor by using _____. |
| A. | the right-hand rule |
| B. | the left-hand rule |
| C. | Lenz's law |
| D. | Faraday's law |
| Answer» B. the left-hand rule | |
| 94. |
The component that produces power in an electromagnetic generator is called the |
| A. | armature |
| B. | field winding |
| C. | commutator |
| D. | brush |
| Answer» B. field winding | |
| 95. |
After the magnetizing force has been removed, the ratio of the remaining magnetic flux to the saturated magnetic flux is called _____________. |
| A. | saturation |
| B. | retentivity |
| C. | hysteresis |
| D. | coercivity |
| Answer» C. hysteresis | |
| 96. |
What do you call the characteristic of a magnetic material whereby a change in magnetization lags the application of a magnetizing force? |
| A. | Hysteresis |
| B. | Induction |
| C. | Retentivity |
| D. | Reluctance |
| Answer» B. Induction | |
| 97. |
Ferromagnetic materials have pre-existing magnetic fields. |
| A. | 1 |
| B. | |
| C. | 1 |
| D. | |
| Answer» C. 1 | |
| 98. |
The polarity of induced voltage while a field is collapsing is |
| A. | independent of the force creating the field |
| B. | opposite to the force creating the field |
| C. | identical to the force creating the field |
| D. | present only if the force is stationary |
| Answer» C. identical to the force creating the field | |
| 99. |
What is the reluctance of a material that has a length of 0.045 m, a cross-sectional area of 0.015 m2, and a permeability of 2500 µWb/At·m? |
| A. | 833.33 µAt/Wb |
| B. | 0.27 At/Wb |
| C. | 1200 At/Wb |
| D. | More information is needed in order to find the reluctance. |
| Answer» D. More information is needed in order to find the reluctance. | |
| 100. |
A group of force lines going from the north pole to the south pole of a magnet is called the magnetic ___. |
| A. | retentivity |
| B. | reluctance |
| C. | hysteresis |
| D. | flux |
| Answer» E. | |