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  • Question

  • 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 Ω load. What is the efficiency of the transformer?


  • Options
  • A. 88%
  • B. 90%
  • C. 92%
  • D. 95%

  • Correct Answer
  • 90% 

    • Transformers problems

    Search Results

    • 1. If the primary power of an ideal transformer having a 2:1 voltage ratio is 100 W, the secondary power is

    • Options
    • A. 100 W
    • B. 50 W
    • C. 75 W
    • D. 200 W
      • Discuss
    • 2. When does maximum power transfer happen from the source to the load?

    • Options
    • A. When the source resistance is greater than the load resistance
    • B. When the source resistance is less than the load resistance
    • C. When there is negligible source resistance
    • D. When the source resistance equals the load resistance
      • Discuss
    • 3. 

      What is the secondary voltage in the given circuit?


    • Options
    • 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
      • Discuss
    • 4. A special transformer used to convert unbalanced signals to balanced signals is the

    • Options
    • A. balun
    • B. autotransformer
    • C. center-tapped transformer
    • D. step-across transformer
      • Discuss
    • 5. 

      What is the power dissipated in the primary of the transformer in the given circuit?


    • Options
    • A. 25 mW
    • B. 500 mW
    • C. 12.5 W
    • D. 62.5 W
      • Discuss
    • 6. The transformer turns ratio determines

    • Options
    • A. the ratio of primary and secondary voltages
    • B. the ratio of primary and secondary currents
    • C. the reflected impedance
    • D. all of the above
      • Discuss
    • 7. Often a common-collector will be the last stage before the load; the main function of this stage is to

    • Options
    • A. provide voltage gain
    • B. buffer the voltage amplifiers from the low-resistance load
    • C. provide phase inversion
    • D. provide a high-frequency path to improve the frequency response
      • Discuss
    • 8. A JFET

    • Options
    • A. is a current-controlled device
    • B. has a low input resistance
    • C. is a voltage-controlled device
    • D. is always forward-biased
      • Discuss
    • 9. To get a negative gate-source voltage in a self-biased JFET circuit, you must use a

    • Options
    • A. voltage divider
    • B. source resistor
    • C. ground
    • D. negative gate supply voltage
      • Discuss
    • 10. A source follower has a voltage gain (Av) of

    • Options
    • A. AV = gmRd
    • B. AV = gmRS
    • C.
    • D.
      • Discuss

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