Transformers And Impedance Matching Quiz

15 Questions | By BATANGMAGALING | Updated: Nov 30, 2022 | Attempts: 645

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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