Transformer Basics and Types Quiz
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Questions and Answers

What is the significance of having the primary and secondary windings close to each other in a transformer?

  • It enhances mutual inductance. (correct)
  • It allows higher voltage operation.
  • It increases the leakage flux.
  • It reduces the number of turns required.

    • What type of coils are typically used in a core type transformer?

  • Square-shaped coils
  • Cylindrical concentric coils (correct)
  • Sandwich coils
  • Layered disk coils

    • How does subdivision of windings into smaller portions affect transformer performance?

  • It decreases current handling capacity.
  • It increases core losses.
  • It reduces leakage flux. (correct)
  • It increases the overall winding resistance.

    • In a typical transformer, where is the low voltage winding usually placed?

    <p>Near the core for ease of insulation.</p> Signup and view all the answers

    What is a primary characteristic of sandwich coils used in transformers?

    <p>They have low voltage portions surrounding the high voltage portion.</p> Signup and view all the answers

    Which factor is primarily considered when classifying transformers?

    <p>The arrangement of the core and windings.</p> Signup and view all the answers

    What material is commonly used for insulating different layers of coils in transformers?

    <p>Paper</p> Signup and view all the answers

    Which design increases the mechanical strength of coils in a transformer?

    <p>Cylindrical concentric coils</p> Signup and view all the answers

    What does a turns ratio of 5:2 signify in a transformer?

    <p>2 volts on the secondary winding for every 5 volts on the primary winding</p> Signup and view all the answers

    What is the role of the primary coil in a transformer?

    <p>It is connected to an AC voltage source.</p> Signup and view all the answers

    What occurs when the current in one coil of a transformer changes uniformly?

    <p>An electromotive force is induced in the secondary coil.</p> Signup and view all the answers

    How is electric energy transferred in a basic transformer setup?

    <p>Entirely through magnetic induction.</p> Signup and view all the answers

    Which statement accurately reflects Faraday's Laws of Electromagnetic Induction in the context of transformers?

    <p>The induced e.m.f. is related to the rate of change of current in the coil.</p> Signup and view all the answers

    Why can't DC currents be used in transformers?

    <p>DC currents cannot change due to constant supply.</p> Signup and view all the answers

    What is the primary voltage if the transformer has 100 primary windings and 350 secondary windings, with a secondary voltage of 700V?

    <p>200V</p> Signup and view all the answers

    In a transformer with 60 primary and 100 secondary windings, if the secondary voltage is 250V, what is the primary voltage?

    <p>150V</p> Signup and view all the answers

    What is the output voltage if a transformer with 50 primary loops and an input voltage of 120V is required to produce 100kV in the secondary?

    <p>100000V</p> Signup and view all the answers

    What is the primary purpose of electric machines?

    <p>To convert between mechanical and electrical energy.</p> Signup and view all the answers

    What is the primary current if the transformer with a primary voltage of 120V draws a current of 10A?

    <p>10A</p> Signup and view all the answers

    When a transformer is described as 'step-up', what is true about its primary and secondary voltages?

    <p>Primary voltage is less than secondary voltage.</p> Signup and view all the answers

    Which of the following machines is classified as a static electrical machine?

    <p>Transformer</p> Signup and view all the answers

    What principle does a transformer operate on?

    <p>Self and mutual induction</p> Signup and view all the answers

    In a step-down transformer, how is the number of secondary windings in comparison to the primary windings?

    <p>It is less than primary windings.</p> Signup and view all the answers

    What must happen to the current in one coil for a transformer to work effectively?

    <p>It must change uniformly.</p> Signup and view all the answers

    What is the main advantage of alternating currents over direct currents?

    <p>They can be easily transformed between different voltage levels.</p> Signup and view all the answers

    Which of the following is NOT a method to generate electricity?

    <p>Electric motors</p> Signup and view all the answers

    During the operation of a transformer, which aspect remains unchanged?

    <p>Frequency</p> Signup and view all the answers

    What is the role of motors in electric machines?

    <p>They convert electrical energy into mechanical energy.</p> Signup and view all the answers

    Which type of electric machine is used to convert mechanical energy into electrical energy?

    <p>Generator</p> Signup and view all the answers

    What is the average e.m.f. per turn according to Faraday's law?

    <p>$4.44f \Phi_m$ volts</p> Signup and view all the answers

    What does the term 'K' represent in the context of transformers?

    <p>The ratio of secondary to primary induced e.m.f.</p> Signup and view all the answers

    How is the R.M.S value of induced e.m.f. for whole secondary windings expressed?

    <p>$N_2 \times 4.44f \Phi_m$ volts</p> Signup and view all the answers

    What is the significance of the factor 1.11 in the context of the R.M.S value?

    <p>It is the factor by which the average value is converted to R.M.S value.</p> Signup and view all the answers

    How does the average e.m.f. per turn relate to the rate of change of flux?

    <p>It is directly proportional to the rate of change of flux.</p> Signup and view all the answers

    What does the term 'turn ratio' refer to in transformer equations?

    <p>The ratio of number of turns in primary to number of turns in secondary</p> Signup and view all the answers

    What occurs to the flux in the core during one quarter of the cycle?

    <p>It increases sinusoidally from zero to maximum.</p> Signup and view all the answers

    What is the formula for the average e.m.f. in the primary winding (E1)?

    <p>$4.44f \Phi_m N_1$ volts</p> Signup and view all the answers

    What is the primary function of a transformer?

    <p>To increase or decrease voltage levels</p> Signup and view all the answers

    In a step-up transformer, how does the number of turns in the primary coil compare to the secondary coil?

    <p>Less than the secondary coil</p> Signup and view all the answers

    What type of current do transformers typically operate with?

    <p>Alternating Current (AC)</p> Signup and view all the answers

    What equation represents the relationship between the input and output voltages of a transformer?

    <p>$E_1/N_1 = E_2/N_2$</p> Signup and view all the answers

    What is the peak value of flux density if the primary voltage is 520 V, with 400 turns, at a frequency of 50 Hz?

    <p>0.976 Wb/m2</p> Signup and view all the answers

    Which of the following components is the main factor that enables a transformer to function?

    <p>Electromagnetic induction</p> Signup and view all the answers

    What happens to the current output when using large voltages in transformer demonstrations?

    <p>Current decreases significantly</p> Signup and view all the answers

    If a transformer has a secondary voltage of 1300 V and a primary voltage of 520 V, what is the ratio of the number of turns between the primary and secondary?

    <p>1:2.5</p> Signup and view all the answers

    Study Notes

    Transformer Basics

    • Transformers are static electrical devices that transfer electrical energy between two circuits
    • They do this without a direct electrical connection
    • The core principle is mutual induction
    • Two coils (primary and secondary) are wound around a ferromagnetic core

    Transformer Types

    • Core type
      • Single magnetic circuit
      • Core is rectangular
      • Windings encircle core
      • Cylindrical coils
    • Shell type
      • Double magnetic circuit
      • Core has three limbs
      • Windings placed on central limb
      • Multilayer disc or sandwich coils
    • Berry type
      • Distributed magnetic circuits
      • More than two magnetic circuits
      • Core construction like spokes of a wheel
      • Symmetrical to shell type
      • Tanks filled with insulating oil

    Transformer Construction

    • Two windings wound on separate limbs
    • Soft iron core provides magnetic circuit
    • Laminated core to reduce eddy currents
    • Insulating materials between windings and core
    • Insulating materials between layers of winding coils

    Principle of Operation

    • Mutual Induction
    • Alternating current (AC) in primary winding creates alternating magnetic flux
    • Changing flux induces voltage in secondary winding
    • Voltage ratio is determined by turns ratio (N2/N1)
      • Step-up transformer = N2>N1; increases voltage
      • Step-down transformer = N2<N1; decreases voltage

    Transformer Equations

    • Voltage ratio (K) = E2/E1 = N2/N1
    • Current ratio = I2/I1 = N1/N2
    • Transformer efficiency is typically high

    Transformer Applications

    • Electrical power distribution (stepping up/down voltage)
    • Industrial machinery
    • Household appliances.

    Transformer Losses

    • Eddy currents in the core (reducing with laminated core)
    • Hysteresis losses in the core (reducing with higher quality core materials)
    • Resistance losses in wires
    • Leakage flux affecting transformer efficiency.

    Transformer Exercises

    • DC cannot be used in transformers because the current does not uniformly change
    • Exercises provided show how to calculate voltage and turns based on the known quantities for primary turns, secondary turns, secondary voltage

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    Related Documents

    Machine Transformer Lecture Notes PDF

    Description

    Test your knowledge on the fundamentals of transformers, including their basic principles, different types, and construction methods. This quiz covers essential concepts such as mutual induction, core types, and the materials used in transformer design.

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