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Transcript
TRANSFORMER 1. 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 2. 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 3. The mutual inductance when k = 0.65, L1 = 2 H, and L2 = 5 H is A. 2 mH B. 2H C. 4H D. 8H 4. 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. 0W C. 250 W D. 2.5 W 5. 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 C. 88 B. 73 V D. 880 V 6. 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. 9V B. 90 V C. 900 V D. 0.9 V 7. 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 8. 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. 1V D. 0V 9. 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. 2V B. 20 V C. 180 V D. 18 V 10. The primary winding of a power transformer should always be A. open B. shorted C. switched D. fused 11. 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 12. 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. 0V B. 6V C. 18 V D. 2V 13. 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 14. 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 15. 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. 0W B. 14.1 W C. 111.5 W D. 1,020 W 16. When a 6 V battery is connected across the primary of a transformer with a turns ratio of 8, the secondary voltage is A. 0V B. 6V C. 48 V 17. 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 18. 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 19. 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 20. The turns ratio required to match an 80 source to a 320 load is A. 80 B. 20 C. 4 D. 2 21. 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 22. 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 23. 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