MCQOPTIONS
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MCQOPTIONS
This section includes 100 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. |
If the supply frequency to the transformer is increased, the iron loss will |
| A. | ot change |
| B. | ecrease |
| C. | ncrease |
| D. | ny of the above |
| Answer» D. ny of the above | |
| 52. |
Delta/star transformer works satisfactorily when |
| A. | oad is balanced only |
| B. | oad is unbalanced only |
| C. | n balanced as well as unbalanced loads |
| D. | one of the above |
| Answer» D. one of the above | |
| 53. |
Star/star transformers work satisfactorily when |
| A. | oad is unbalanced only |
| B. | oad is balanced only |
| C. | n balanced as well as unbalanced loads |
| D. | one of the above |
| Answer» C. n balanced as well as unbalanced loads | |
| 54. |
The changes in volume of transformer cooling oil due to variation of atmospheric tem-perature during day and night is taken care of by which part of transformer |
| A. | onservator |
| B. | reather |
| C. | ushings |
| D. | uchholz relay |
| Answer» B. reather | |
| 55. |
In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are |
| A. | riction and windage losses |
| B. | opper losses |
| C. | ysteresis and eddy current losses |
| D. | one of the above |
| Answer» D. one of the above | |
| 56. |
In an actual transformer the iron loss remains practically constant from noload to fullload because |
| A. | alue of transformation ratio remains constant |
| B. | ermeability of transformer core remains constant |
| C. | ore flux remains practically constant |
| D. | rimary voltage remains constant |
| Answer» D. rimary voltage remains constant | |
| 57. |
For given applied voltage, with the increase in frequency of the applied voltage |
| A. | ddy current loss will decrease |
| B. | ddy current loss will increase |
| C. | ddy current loss will remain unchanged |
| D. | one of the above |
| Answer» D. one of the above | |
| 58. |
Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds |
| A. | 0°C |
| B. | 0°C |
| C. | 00°C |
| D. | 50°C |
| Answer» E. | |
| 59. |
Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in |
| A. | hort-circuiting of the secondaries |
| B. | ower factor of one of the transformers is leading while that of the other lagging |
| C. | ransformers having higher copper losses will have negligible core losses |
| D. | oading of the transformers not in proportion to their kVA ratings |
| Answer» E. | |
| 60. |
The function of breather in a transformer is |
| A. | o provide oxygen inside the tank |
| B. | o cool the coils during reduced load |
| C. | o cool the transformer oil |
| D. | o arrest flow of moisture when outside air enters the transformer |
| Answer» E. | |
| 61. |
Part of the transformer which is most subject to damage from overheating is |
| A. | ron core |
| B. | opper winding |
| C. | inding insulation |
| D. | rame or case |
| Answer» D. rame or case | |
| 62. |
Which of the following loss in a transformer is zero even at full load ? |
| A. | ore loss |
| B. | riction loss |
| C. | ddy current loss |
| D. | ysteresis loss |
| Answer» C. ddy current loss | |
| 63. |
A transformer cannot raise or lower the voltage of a D.C. supply because |
| A. | here is no need to change the D.C. voltage |
| B. | D.C. circuit has more losses |
| C. | araday's laws of electromagnetic induction are not valid since the rate of change of flux is zero |
| D. | one of the above |
| Answer» D. one of the above | |
| 64. |
The size of a transformer core will depend on |
| A. | requency |
| B. | rea of the core |
| C. | lux density of the core material |
| D. | and (B) both |
| Answer» E. | |
| 65. |
The purpose of providing iron core in a step-up transformer is |
| A. | o provide coupling between primary and secondary |
| B. | o increase the magnitude of mutual flux |
| C. | o decrease the magnitude of magnetizing current |
| D. | o provide all above features |
| Answer» D. o provide all above features | |
| 66. |
A transformer has a 1:6 turns ratio and a secondary coil load resistance of 470 Ω. The load resistance as seen by the source is |
| A. | .3 Ω |
| B. | .8 Ω |
| C. | 8 Ω |
| D. | 3 Ω |
| Answer» E. | |
| 67. |
The primary coil of a transformer is connected to a 60 V ac source. The secondary coil is connected to a 330 Ω load. The turns ratio is 3:1. What is the secondary voltage? |
| A. | V |
| B. | 0 V |
| C. | 80 V |
| D. | 8 V |
| Answer» C. 80 V | |
| 68. |
If a transformer is continuously operated the maximum temperature rise will occur in |
| A. | ore |
| B. | indings |
| C. | ank |
| D. | ny of the above |
| Answer» C. ank | |
| 69. |
When a given transformer is run at its rated voltage but reduced frequency, its |
| A. | lux density remains unaffected |
| B. | ron losses are reduced |
| C. | ore flux density is reduced |
| D. | ore flux density is increased |
| Answer» E. | |
| 70. |
Which of the following does not change in an ordinary transformer? |
| A. | requency |
| B. | oltage |
| C. | urrent |
| D. | ny of the above |
| Answer» B. oltage | |
| 71. |
Two transformers operating in parallel will share the load depending upon their |
| A. | eakage reactance |
| B. | er unit impedance |
| C. | fficiencies |
| D. | atings |
| Answer» C. fficiencies | |
| 72. |
If R₂ is the resistance of secondary winding of the transformer and K is the transformation ratio then the equivalent secondary resistance referred to primary will be |
| A. | ₂/√K |
| B. | ₂/K² |
| C. | ₂²/K² |
| D. | ₂²/K |
| Answer» C. ₂²/K² | |
| 73. |
Which of the following is not a routine test on transformers? |
| A. | ore insulation voltage test |
| B. | mpedance test |
| C. | adio interference test |
| D. | olarity test |
| Answer» D. olarity test | |
| 74. |
An ideal transformer has infinite values of primary and secondary inductances. The statement is |
| A. | rue |
| B. | alse |
| Answer» C. | |
| 75. |
When the equivalent circuit diagram of doouble squirrelcage induction motor is constructed the two cages can be considered |
| A. | n series |
| B. | n parallel |
| C. | n series-parallel |
| D. | n parallel with stator |
| Answer» C. n series-parallel | |
| 76. |
Which of the following is not the standard voltage for power supply in India? |
| A. | lkV |
| B. | 3kV |
| C. | 6 kV |
| D. | 22 kV |
| Answer» E. | |
| 77. |
Buchholz's relay gives warning and protection against |
| A. | lectrical fault inside the transformer itself |
| B. | lectrical fault outside the transformer in outgoing feeder |
| C. | or both outside and inside faults |
| D. | one of the above |
| Answer» B. lectrical fault outside the transformer in outgoing feeder | |
| 78. |
In the transformer following winding has got more cross-sectional area |
| A. | ow voltage winding |
| B. | igh voltage winding |
| C. | rimary winding |
| D. | econdary winding |
| Answer» B. igh voltage winding | |
| 79. |
An ideal transformer will have maximum efficiency at a load such that |
| A. | opper loss = iron loss |
| B. | opper loss < iron loss |
| C. | opper loss > iron loss |
| D. | one of the above |
| Answer» B. opper loss < iron loss | |
| 80. |
If the percentage impedances of the two transformers working in parallel are different, then |
| A. | ransformers will be overheated |
| B. | ower factors of both the transformers will be same |
| C. | arallel operation will be not possible |
| D. | arallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load |
| Answer» E. | |
| 81. |
A good voltage regulation of a transformer means |
| A. | utput voltage fluctuation from no load to full load is least |
| B. | utput voltage fluctuation with power factor is least |
| C. | ifference between primary and secondary voltage is least |
| D. | ifference between primary and secondary voltage is maximum |
| Answer» B. utput voltage fluctuation with power factor is least | |
| 82. |
To step 110 V ac down to 20 V ac, the turns ratio must be |
| A. | 5.5 |
| B. | 18 |
| C. | 0.18 |
| D. | 0.018 |
| Answer» D. 0.018 | |
| 83. |
A step-down transformer has a turns ratio less than 1. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 84. |
The primary coil of a transformer is connected to a 60 V ac source. The secondary coil is connected to a 330 load. The turns ratio is 3:1. What is the secondary voltage? |
| A. | 2 V |
| B. | 20 V |
| C. | 180 V |
| D. | 18 V |
| Answer» C. 180 V | |
| 85. |
When a 200 load resistor is connected across the secondary winding of a transformer with a turns ratio of 4, the source "sees" a reflective load of |
| A. | 50 |
| B. | 12.5 |
| C. | 800 |
| D. | 0 |
| Answer» C. 800 | |
| 86. |
What is the coefficient of coupling for a transformer in which 4% of the total flux generated in the primary does not pass through the secondary? |
| A. | 0.4 |
| B. | 4 |
| C. | 9.6 |
| D. | 0.96 |
| Answer» E. | |
| 87. |
A transformer |
| A. | changes ac to dc |
| B. | changes dc to ac |
| C. | steps up or down dc voltages |
| D. | steps up or down ac voltages |
| Answer» E. | |
| 88. |
The primary is the winding connected to the source, and the secondary is the winding connected to the load. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 89. |
In a certain loaded transformer, the secondary voltage is one-fourth the primary voltage. The secondary current is |
| A. | one-fourth the primary current |
| B. | four times the primary current |
| C. | equal to the primary current |
| D. | one-fourth the primary current and equal to the primary current |
| Answer» C. equal to the primary current | |
| 90. |
The mutual inductance when k = 0.65, L1 = 2 H, and L2 = 5 H is |
| A. | 2 mH |
| B. | 2 H |
| C. | 4 H |
| D. | 8 H |
| Answer» C. 4 H | |
| 91. |
The turns ratio required to match an 80 source to a 320 load is |
| A. | 80 |
| B. | 20 |
| C. | 4 |
| D. | 2 |
| Answer» E. | |
| 92. |
In a certain transformer, the input power to the primary is 120 W. If 8.5 W are lost to the winding resistance, what is the output power to the load, neglecting any other issues? |
| A. | 0 W |
| B. | 14.1 W |
| C. | 111.5 W |
| D. | 1,020 W |
| Answer» D. 1,020 W | |
| 93. |
A certain transformer has 400 turns in the primary winding and 2,000 turns in the secondary winding. The turns ratio is |
| A. | 0.2 |
| B. | 0.4 |
| C. | 5 |
| D. | 25 |
| Answer» D. 25 | |
| 94. |
If a transformer has 50 turns in the primary winding and 10 turns in the secondary winding, what is the reflective resistance if the secondary load resistance is 250 ? |
| A. | 250 |
| B. | 25 |
| C. | 6250 |
| D. | 62500 |
| Answer» D. 62500 | |
| 95. |
A certain amplifier has 600 internal resistance looking from its output. In order to provide maximum power to a 4 speaker, what turns ratio must be used in the coupling transformer? |
| A. | 8 |
| B. | 0.8 |
| C. | 0.08 |
| D. | 80 |
| Answer» D. 80 | |
| 96. |
When the turns ratio of a transformer is 20 and the primary ac voltage is 12 V, the secondary voltage is |
| A. | 12 V |
| B. | 120 V |
| C. | 240 V |
| D. | 2,400 V |
| Answer» D. 2,400 V | |
| 97. |
How many primary volts must be applied to a transformer with a turns ratio of 0.1 to obtain a secondary voltage of 9 V? |
| A. | 9 V |
| B. | 90 V |
| C. | 900 V |
| D. | 0.9 V |
| Answer» C. 900 V | |
| 98. |
If the voltage is stepped up, the current is stepped down, and vice versa. |
| A. | 1 |
| B. | |
| C. | 1 |
| D. | |
| Answer» B. | |
| 99. |
The primary winding of a transformer has 110 V ac across it. What is the secondary voltage if the turns ratio is 8? |
| A. | 8.8 V |
| B. | 88 V |
| C. | 880 V |
| D. | 8,800 V |
| Answer» D. 8,800 V | |
| 100. |
What kVA rating is required for a transformer that must handle a maximum load current of 8 A with a secondary voltage of 2 kV? |
| A. | 4 kVA |
| B. | 0.25 kVA |
| C. | 16 kVA |
| D. | 8 kVA |
| Answer» D. 8 kVA | |