MCQOPTIONS
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MCQOPTIONS
This section includes 79 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
Reciprocal of permeability is |
| A. | eluctivity |
| B. | usceptibility |
| C. | ermittivity |
| D. | onductance |
| Answer» B. usceptibility | |
| 52. |
The direction of magnetic lines of force is |
| A. | rom south pole to north pole |
| B. | rom north pole to south pole |
| C. | rom one end of the magnet to another |
| D. | one of the above |
| Answer» C. rom one end of the magnet to another | |
| 53. |
A material which is slightly repelled by a magnetic field is known as |
| A. | erromagnetic material |
| B. | iamagnetic material |
| C. | aramagnetic material |
| D. | onducting material |
| Answer» C. aramagnetic material | |
| 54. |
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. | ero |
| B. | LI |
| C. | 2LI |
| D. | LI2 |
| Answer» B. LI | |
| 55. |
The relative permeability is less than unity is case of |
| A. | erromagnetic materials |
| B. | errites |
| C. | on-ferrous materials |
| D. | iamagnetic materials |
| Answer» E. | |
| 56. |
The magnetomotive force is |
| A. | he voltage across the two ends of exciting coil |
| B. | he flow of an electric current |
| C. | he sum of all currents embraced by one line of magnetic field |
| D. | he passage of magnetic field through an exciting coil |
| Answer» D. he passage of magnetic field through an exciting coil | |
| 57. |
Indicate which of the following material does not retain magnetism permanently. |
| A. | oft iron |
| B. | tainless steel |
| C. | ardened steel |
| D. | one of the above |
| Answer» B. tainless steel | |
| 58. |
What is the magneto-motive force in a 75-turn coil of wire when there are 4 A of current through it? |
| A. | 8.75 At |
| B. | 0 At |
| C. | 00 At |
| D. | 87 At |
| Answer» D. 87 At | |
| 59. |
Strength of an electromagnet can be increased by |
| A. | ncreasing the cross-sectional area |
| B. | ncreasing the number of turns |
| C. | ncreasing current supply |
| D. | ll above methods |
| Answer» E. | |
| 60. |
Magnetism of a magnet can be destroyed by |
| A. | eating |
| B. | ammering |
| C. | y inductive action of another magnet |
| D. | y all above methods |
| Answer» E. | |
| 61. |
A basic one-loop dc generator is rotated at 90 rev/s. How many times each second does the dc output voltage peak (reach maximum)? |
| A. | 90 |
| B. | 180 |
| C. | 270 |
| D. | 360 |
| Answer» C. 270 | |
| 62. |
If a conductor is moved back and forth at a constant rate in a constant magnetic field, the voltage in the conductor will reverse polarity. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 63. |
The voltage induced across a certain coil is 200 mV. A 120 resistor is connected to the coil terminals. The induced current is |
| A. | 1.7 mA |
| B. | 16 mA |
| C. | 12 mA |
| D. | 120 mA |
| Answer» B. 16 mA | |
| 64. |
What is the flux density when the flux is 5.5 Wb and the cross-sectional area is 6 × 10–3 m2? |
| A. | 91.7 T |
| B. | 917 T |
| C. | 91 T |
| D. | 9.7 T |
| Answer» C. 91 T | |
| 65. |
The unit for reluctance is |
| A. | tesla |
| B. | At/Wb |
| C. | At/m |
| D. | Wb |
| Answer» C. At/m | |
| 66. |
If the steel disk in a crankshaft position sensor has stopped with the tab in the magnet's air gap, the induced voltage |
| A. | increases |
| B. | decreases |
| C. | is zero |
| D. | will remain constant |
| Answer» D. will remain constant | |
| 67. |
What is the flux density in a magnetic field in which the flux in 0.1 m2 is 600 Wb? |
| A. | 6,000 T |
| B. | 600 T |
| C. | 600 T |
| D. | 6 T |
| Answer» B. 600 T | |
| 68. |
Materials with a low retentivity do not retain a magnetic field very well. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 69. |
If a loop in a basic dc generator suddenly begins rotating at a faster speed, the induced voltage |
| A. | remains unchanged |
| B. | reverses polarity |
| C. | increases |
| D. | decreases |
| Answer» D. decreases | |
| 70. |
The induced voltage across a coil with 250 turns that is located in a magnetic field that is changing at a rate of 8 Wb/s is |
| A. | 1,000 V |
| B. | 2,000 V |
| C. | 31.25 V |
| D. | 3,125 V |
| Answer» C. 31.25 V | |
| 71. |
What is the reluctance of a material that has a length of 0.07 m, a cross-sectional area of 0.014 m2, and a permeability of 4,500 Wb/At √ó m? |
| A. | 1111 At/Wb |
| B. | 111 At/Wb |
| C. | 11 At/Wb |
| D. | 1 At/Wb |
| Answer» B. 111 At/Wb | |
| 72. |
When the current through the coil of an electromagnet reverses, the |
| A. | direction of the magnetic field reverses |
| B. | direction of the magnetic field remains unchanged |
| C. | magnetic field expands |
| D. | magnetic field collapses |
| Answer» B. direction of the magnetic field remains unchanged | |
| 73. |
An electromagnetic field exists only when there is |
| A. | an increasing current |
| B. | decreasing current |
| C. | voltage |
| D. | current |
| Answer» E. | |
| 74. |
Lenz's law defines the polarity of the induced voltage. |
| A. | 1 |
| B. | |
| C. | 1 |
| D. | |
| Answer» B. | |
| 75. |
If the cross-sectional area of a magnetic field increases, but the flux remains the same, the flux density |
| A. | increases |
| B. | decreases |
| C. | remains the same |
| D. | doubles |
| Answer» C. remains the same | |
| 76. |
The direction of a magnetic field within a magnet is |
| A. | from south to north |
| B. | from north to south |
| C. | back to front |
| D. | front to back |
| Answer» B. from north to south | |
| 77. |
For a given wirewound core, an increase in current through the coil |
| A. | reverses the flux lines |
| B. | decreases the flux density |
| C. | increases the flux density |
| D. | causes no change in flux density |
| Answer» D. causes no change in flux density | |
| 78. |
There is 900 mA of current through a wire with 40 turns. What is the reluctance of the circuit if the flux is 400 Wb? |
| A. | 14,400 At/Wb |
| B. | 1,440 At/Wb |
| C. | 9,000 At/Wb |
| D. | 90,000 At/Wb |
| Answer» E. | |
| 79. |
When the speed at which a conductor is moved through a magnetic field is increased, the induced voltage |
| A. | increases |
| B. | decreases |
| C. | remains constant |
| D. | reaches zero |
| Answer» B. decreases | |