Analyse quantitatively the operation of ideal transformers

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  • By using Faraday’s Law of induction, It can be shown that the rate of change of flux due to an alternating input current is : Faraday’s Law of induction
    • where Vp is input voltage
    • Np is the number of winding in the primary coil
  • By using Faraday’s Law of induction, It can be shown that the voltage developed in the secondary coil due to changing flux experience is : Faraday’s Law of induction
  • In an ideal transformer, changing flux that is experienced by the secondary coil is the same changing flux due to the primary coil.
  • Therefore
    • equations of transformers
  • These are the equations of transformers.
    • equations of transformers
    • If Ns is greater than Np, then it is known as Step-Up transformer
    • If Ns is smaller than Np, it is known as Step-Down Transformer.

Energy conservation in an Ideal Transformer

  • Energy is transferred from the primary coil to the secondary coil.
  • In an ideal transformer, there is no loss during this transfer of energy.
  • If there is no loss , then power in the secondary and primary coil are same.
    • Equation of power : P = VI
    • Thus, VpIp = VsIs
  • This allows us to understand how low voltage in input coil can give higher voltage on output coil in Step-Up Transformer
  • equations of transformers
    • equations of transformers

Extract from Physics Stage 6 Syllabus © 2017 NSW Education Standards Authority (NESA)