Transformers And Impedance Matching Quiz

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Transformers And Impedance Matching Quiz - Quiz

To test and expand your knowledge, take this transformers and impedance matching quiz that we have designed for you. Impedance-matching transformers are used for the purpose of matching the impedance of a source and of its load to get the most efficient transfer of energy. Isolation transformers are mostly applied for reasons of safety to separate a piece of equipment from the power source. So, learn more with these questions, and we wish you good luck.


Questions and Answers
  • 1. 
    In a step-up transformer,
    • A. 

      The primary impedance is greater than the secondary impedance.

    • B. 

      The secondary winding is right on top of the primary.

    • C. 

      The primary voltage is less than the secondary voltage.

    • D. 

      All of the above are true.

  • 2. 
    A transformer steps a voltage down from 117 V to 6.00 V. What is its primary-to-secondaryturns ratio?
    • A. 

      1:380

    • B. 

      380:1

    • C. 

      1:19.5

    • D. 

      19.5:1

  • 3. 
    A step-up transformer has a primary-to-secondary turns ratio of 1:5.00. If 117 V rms appearsat the primary, what is the ac rms voltage across the secondary?
    • A. 

      23.4 V rms

    • B. 

      585 V rms

    • C. 

      117 V rms

    • D. 

      2.93 kV rms

  • 4. 
    A transformer has a secondary-to-primary turns ratio of 0.167. This transformer is
    • A. 

      A step-up unit.

    • B. 

      A step-down unit.

    • C. 

      Neither a step-up unit nor a step-down unit.

    • D. 

      A reversible unit.

  • 5. 
    Eddy currents cause
    • A. 

      An increase in efficiency.

    • B. 

      An increase in coupling between windings.

    • C. 

      An increase in core loss.

    • D. 

      An increase in usable frequency range.

  • 6. 
    The shell method of transformer winding
    • A. 

      Provides maximum coupling.

    • B. 

      Minimizes capacitance between windings.

    • C. 

      Withstands more voltage than other winding methods.

    • D. 

      Has windings far apart but along a common axis.

  • 7. 
    Which of these core types is best if you need a winding inductance of 1.5 H?
    • A. 

      Air core

    • B. 

      Ferromagnetic solenoid core

    • C. 

      Ferromagnetic toroid core

    • D. 

      Ferromagnetic pot core

  • 8. 
    An advantage of a toroid core over a solenoid core is the fact that
    • A. 

      The toroid works at higher frequencies.

    • B. 

      The toroid confines the magnetic flux.

    • C. 

      The toroid can work for dc as well as for ac.

    • D. 

      It is easier to wind the turns on a toroid.

  • 9. 
    High voltage is used in long-distance power transmission because
    • A. 

      It is easier to regulate than low voltage.

    • B. 

      The I^2 R losses are minimized.

    • C. 

      The electromagnetic fields are strong.

    • D. 

      Small transformers can be used.

  • 10. 
    In a household circuit, 234-V rms electricity usually has
    • A. 

      One phase.

    • B. 

      Two phases.

    • C. 

      Three phases.

    • D. 

      Four phases.

  • 11. 
    In a transformer, a center tap often exists in
    • A. 

      The primary winding.

    • B. 

      The secondary winding.

    • C. 

      An unbalanced winding.

    • D. 

      A balanced winding.

  • 12. 
    An autotransformer
    • A. 

      Can be adjusted automatically.

    • B. 

      Has a center-tapped secondary.

    • C. 

      Consists of a single tapped winding.

    • D. 

      Is useful only for impedance matching.

  • 13. 
    Suppose a transformer has a primary-to-secondary turns ratio of 2.00:1. The inputimpedance is 300 Ω, purely resistive. What is the output impedance?
    • A. 

      75 Ω, purely resistive

    • B. 

      150 Ω, purely resistive

    • C. 

      600 Ω, purely resistive

    • D. 

      1200 Ω, purely resistive

  • 14. 
    Suppose a purely resistive input impedance of 50 Ω must be matched to a purely resistiveoutput impedance of 450 Ω. The primary-to-secondary turns ratio of the transformer must bewhich of the following?
    • A. 

      9.00

    • B. 

      3.00

    • C. 

      1/3.00

    • D. 

      1/9.00

  • 15. 
    Suppose a quarter-wave matching section has a characteristic impedance of 75.0 Ω. Theinput impedance is 50.0 Ω, purely resistive. What is the output impedance?
    • A. 

      150 Ω, purely resistive

    • B. 

      125 Ω, purely resistive

    • C. 

      100 Ω, purely resistive

    • D. 

      113 Ω, purely resistive

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