MCQOPTIONS
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MCQOPTIONS
This section includes 123 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
The turns ratio required to match an 80 source to a 320 load is |
| A. | 80 |
| B. | 20 |
| C. | 4 |
| D. | 2 |
| Answer» E. | |
| 2. |
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. | 6,250 |
| D. | 62,500 |
| Answer» D. 62,500 | |
| 3. |
A transformer has a 1:6 turns ratio and a secondary coil load resistance of 470 . The load resistance as seen by the source is |
| A. | 1.3 |
| B. | 7.8 |
| C. | 78 |
| D. | 13 |
| Answer» E. | |
| 4. |
The primary of a transformer is connected to a 6 V battery. The turns ratio is 1:3 and the secondary load, , is 100 . The voltage across the load is |
| A. | 0 V |
| B. | 6 V |
| C. | 18 V |
| D. | 2 V |
| Answer» B. 6 V | |
| 5. |
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 | |
| 6. |
A transformer with a 110 V primary has a 15:1 turns ratio. The load resistance, , is 120 . What is the approximate voltage across the load? |
| A. | 7.3 V |
| B. | 73 V |
| C. | 88 V |
| D. | 880 V |
| Answer» B. 73 V | |
| 7. |
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 | |
| 8. |
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 | |
| 9. |
Losses which occur in rotating electric machines and do not occur in trans formers are |
| A. | friction and windage losses |
| B. | magnetic losses |
| C. | hysteresis and eddy current losses |
| D. | copper losses |
| Answer» B. magnetic losses | |
| 10. |
In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are |
| A. | hysteresis and eddy current losses |
| B. | friction and windage losses |
| C. | copper losses |
| D. | none of the above |
| Answer» B. friction and windage losses | |
| 11. |
The secondary of a current transformer is always short-circuited under operating conditions because it |
| A. | avoids core saturation and high voltage induction |
| B. | is safe to human beings |
| C. | protects the primary circuit |
| D. | none of the above |
| Answer» B. is safe to human beings | |
| 12. |
Which of the following protection is normally not provided on small distribution transformers ? |
| A. | Overfluxing protection |
| B. | Buchholz relay |
| C. | Overcurrent protection |
| D. | All of the above |
| Answer» C. Overcurrent protection | |
| 13. |
If a transformer is continuously operated the maximum temperature rise will occur in |
| A. | core |
| B. | windings |
| C. | tank |
| D. | any of the above |
| Answer» C. tank | |
| 14. |
In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of |
| A. | less than 15 A |
| B. | more than 15 A |
| C. | 15 A |
| D. | none of the above |
| Answer» B. more than 15 A | |
| 15. |
Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is |
| A. | approximately equal to one |
| B. | less than one |
| C. | great than one |
| D. | none of the above |
| Answer» B. less than one | |
| 16. |
The efficiencies of transformers compared with that of electric motors of the same power are |
| A. | about the same |
| B. | much smaller |
| C. | much higher |
| D. | somewhat smaller |
| Answer» D. somewhat smaller | |
| 17. |
In an actual transformer the iron loss remains practically constant from noload to fullload because |
| A. | value of transformation ratio remains constant |
| B. | permeability of transformer core remains constant |
| C. | core flux remains practically constant |
| D. | primary voltage remains constant |
| Answer» D. primary voltage remains constant | |
| 18. |
The full-load copper loss of a trans former is 1600 W. At half-load, the copper loss will be |
| A. | 6400 W |
| B. | 1600 W |
| C. | 800 W |
| D. | 400 W |
| Answer» E. | |
| 19. |
An ideal transformer has infinite values of primary and secondary inductances. The statement is |
| A. | true |
| B. | false |
| C. | none |
| D. | none |
| Answer» C. none | |
| 20. |
The efficiency of two identical transformers under load conditions can be determined by |
| A. | short-circuit test |
| B. | back-to-back test |
| C. | open circuit test |
| D. | any of the above |
| Answer» C. open circuit test | |
| 21. |
In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are |
| A. | friction and windage losses |
| B. | copper losses |
| C. | hysteresis and eddy current losses |
| D. | none of the above |
| Answer» D. none of the above | |
| 22. |
The no load current in a transformer lags behind the applied voltage by an angle of about |
| A. | 180 |
| B. | 120" |
| C. | 90 |
| D. | 75 |
| Answer» E. | |
| 23. |
A common method of cooling a power transformer is_______________? |
| A. | natural air cooling |
| B. | air blast cooling |
| C. | oil cooling |
| D. | any of the above |
| Answer» D. any of the above | |
| 24. |
A Buchholz relay can be installed on______________? |
| A. | auto-transformers |
| B. | air-cooled transformers |
| C. | welding transformers |
| D. | oil cooled transformers |
| Answer» E. | |
| 25. |
The voltage V2 is _____ in the given circuit. |
| A. | 36.7 V |
| B. | 73.3 V |
| C. | 110 V |
| D. | 220 V |
| Answer» B. 73.3 V | |
| 26. |
The reflected resistance is ___ as seen by the source in the given circu. |
| A. | 150 |
| B. | 300 |
| C. | 600 |
| D. | 2.4 k |
| Answer» E. | |
| 27. |
The secondary current is _____ in the given circuit. |
| A. | 1.9 mA |
| B. | 7.5 mA |
| C. | 30 mA |
| D. | 60 mA |
| Answer» D. 60 mA | |
| 28. |
In the given circuit, Maximum power is being transferred to the load. |
| A. | True |
| B. | False |
| Answer» C. | |
| 29. |
The secondary voltages produced by a center-tapped transformer are equal in amplitude but 180° out of phase with respect to the center tap. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 30. |
In the given circuit, the secondary voltage is in phase with the primary voltage. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 31. |
If the load doubled in value in the given circuit, what reflected resistance would the source see? |
| A. | 80 |
| B. | 400 |
| C. | 2 k |
| D. | 10 k |
| Answer» B. 400 | |
| 32. |
What is the secondary voltage in the given circuit? |
| A. | 13.3 V rms in phase with the primary |
| B. | 120 V rms in phase with the primary |
| C. | 13.3 V rms out of phase with the primary |
| D. | 120 V rms out of phase with the primary |
| Answer» D. 120 V rms out of phase with the primary | |
| 33. |
What is the power dissipated in the primary of the transformer in the given circuit? |
| A. | 25 mW |
| B. | 500 mW |
| C. | 12.5 W |
| D. | 62.5 W |
| Answer» E. | |
| 34. |
What is the current through the load in the given circuit? |
| A. | 500 A |
| B. | 10 mA |
| C. | 250 mA |
| D. | 1.25 A |
| Answer» D. 1.25 A | |
| 35. |
A transformer responds only to dc. |
| A. | True |
| B. | False |
| Answer» C. | |
| 36. |
A reflective load is a load as it appears to the source in the primary of a transformer. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 37. |
A center tap (CT) is a connection at the midpoint of the secondary winding of a transformer. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 38. |
An autotransformer is one in which the primary and secondary are automatically coupled. |
| A. | True |
| B. | False |
| Answer» C. | |
| 39. |
A transformer changes ac to dc. |
| A. | True |
| B. | False |
| Answer» C. | |
| 40. |
A step-up transformer steps up power. |
| A. | True |
| B. | False |
| Answer» C. | |
| 41. |
A transformer consists of two or more cores that are electrically coupled on a common core. |
| A. | True |
| B. | False |
| Answer» C. | |
| 42. |
A transformer with a 110 V primary has a 15:1 turns ratio. The load resistance, RL, is 120 . What is the approximate voltage across the load? |
| A. | 7.3 V |
| B. | 73 V |
| C. | 88 V |
| D. | 880 V |
| Answer» B. 73 V | |
| 43. |
The primary of a transformer is connected to a 6 V battery. The turns ratio is 1:3 and the secondary load, RL, is 100 . The voltage across the load is |
| A. | 0 V |
| B. | 6 V |
| C. | 18 V |
| D. | 2 V |
| Answer» B. 6 V | |
| 44. |
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 | |
| 45. |
The use of higher flux density in the transformer design |
| A. | Reduces weight per KVA |
| B. | Reduces iron losses |
| C. | Reduces copper losses |
| D. | Increases part load efficiency |
| Answer» B. Reduces iron losses | |
| 46. |
A transformer oil must be free from |
| A. | Sludge |
| B. | Odour |
| C. | Gases |
| D. | Moisture |
| Answer» E. | |
| 47. |
Distribution transformers are generally designed for maximum efficiency around |
| A. | 90% load |
| B. | Zero load |
| C. | 25% load |
| D. | 50% load |
| Answer» E. | |
| 48. |
While conducting short-circuit test on a transformer the following side is short-circuited |
| A. | High voltage side |
| B. | Low voltage side |
| C. | Primary side |
| D. | Secondary side |
| Answer» C. Primary side | |
| 49. |
A transformer core is laminated to |
| A. | Reduce hysteresis loss |
| B. | . Reduce eddy current losses |
| C. | Reduce copper losses |
| D. | Reduce all above losses |
| Answer» C. Reduce copper losses | |
| 50. |
During open circuit test of a transformer |
| A. | Primary is supplied rated voltage |
| B. | Primary is supplied full load current |
| C. | . Primary is supplied current at reduced voltage |
| D. | Primary is supplied rated kVA |
| Answer» B. Primary is supplied full load current | |