MCQOPTIONS
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MCQOPTIONS
This section includes 20 Mcqs, each offering curated multiple-choice questions to sharpen your Alternating Current and Voltage knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Magnetizing impedance of a transformer is determined by |
| A. | Open circuit test |
| B. | Short circuit test |
| C. | None of these |
| D. | Both open circuit and short circuit tests |
| Answer» B. Short circuit test | |
| 2. |
In a transformer, the exciting current will be in phase quadrature with the impressed voltage provided |
| A. | Only the core loss is ignored |
| B. | Only the leakage impedance drop is ignored |
| C. | Only no-load copper loss is ignored |
| D. | Both the leakage and impedance drop and the core loss are ignored |
| Answer» B. Only the leakage impedance drop is ignored | |
| 3. |
The open circuit All-day efficiency of a transformer is |
| A. | Less than its power efficiency |
| B. | Equal to its power efficiency |
| C. | None of these |
| D. | More than its power efficiency |
| Answer» B. Equal to its power efficiency | |
| 4. |
If a sinusoidal exciting current is applied to a transformer, the mutual flux produced is |
| A. | Sinusoidal |
| B. | Negative |
| C. | Flat top |
| D. | Zero |
| Answer» D. Zero | |
| 5. |
The full-load efficiency of a transformer at 0.85 p.f. lag is 97 per cent. Its efficiency at full load 0.85 bpower factor lead will be |
| A. | 0.96 |
| B. | 0.99 |
| C. | 0.98 |
| D. | 0.97 |
| Answer» E. | |
| 6. |
What is the turns ratio of the transformer needed to match a 1 k source resistance to a 160 load? |
| A. | 2.5:1 |
| B. | 0.4:1 |
| C. | 6.25:1 |
| D. | 16:1 |
| Answer» C. 6.25:1 | |
| 7. |
A transformer is plugged into a 120 V rms source and has a primary current of 300 mA rms. The secondary is providing 18 V across a 10 load. What is the efficiency of the transformer? |
| A. | 88% |
| B. | 90% |
| C. | 92% |
| D. | 95% |
| Answer» C. 92% | |
| 8. |
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. | |
| 9. |
When a 6 V battery is connected across the primary of a transformer with a turns ratio of 8, the secondary voltage is |
| A. | 0 V |
| B. | 6 V |
| C. | 48 V |
| D. | 0.75 V |
| Answer» B. 6 V | |
| 10. |
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 | |
| 11. |
The primary of a transformer is connected to a 6 V battery. The turns ratio is 1:3 and the secondary load, R L , is 100 . The voltage across the load is |
| A. | 0 V |
| B. | 6 V |
| C. | 18 V |
| D. | 2 V |
| Answer» B. 6 V | |
| 12. |
To step 120 V ac up to 900 V ac, the turns ratio must be |
| A. | 75 |
| B. | 750 |
| C. | 7.5 |
| D. | 0.13 |
| Answer» D. 0.13 | |
| 13. |
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 | |
| 14. |
The primary winding of a power transformer should always be |
| A. | open |
| B. | shorted |
| C. | switched |
| D. | fused |
| Answer» E. | |
| 15. |
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 | |
| 16. |
A certain transformer has a turns ratio of 1 and a 0.85 coefficient of coupling. When 2 V ac is applied to the primary, the secondary voltage is |
| A. | 1.7 V |
| B. | 0.85 V |
| C. | 1 V |
| D. | 0 V |
| Answer» B. 0.85 V | |
| 17. |
A transformer with a 110 V primary has a 15:1 turns ratio. The load resistance, R L , 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 | |
| 18. |
If 25 W of power are applied to the primary of an ideal transformer with a turns ratio of 10, the power delivered to the secondary load is |
| A. | 25 W |
| B. | 0 W |
| C. | 250 W |
| D. | 2.5 W |
| Answer» B. 0 W | |
| 19. |
The mutual inductance when k = 0.65, L 1 = 2 H, and L 2 = 5 H is |
| A. | 2 mH |
| B. | 2 H |
| C. | 4 H |
| D. | 8 H |
| Answer» C. 4 H | |
| 20. |
The turns ratio required to match an 80 source to a 320 load is |
| A. | 80 |
| B. | 20 |
| C. | 4 |
| D. | 2 |
| Answer» E. | |