1. A transformer is an electrical device used to change the voltage levels in an AC circuit.
  2. It operates on the principle of electromagnetic induction and mutual induction between two coils.

Working Principle of a Transformer

  • Based on Faraday's laws of electromagnetic induction, a varying current in the primary coil produces a varying magnetic flux.
  • This magnetic flux links to the secondary coil through a common core, inducing an EMF in the secondary coil.
  • The transformer works only with AC (alternating current), as a constant DC current does not produce changing magnetic flux.
  • The relationship between primary and secondary voltages is given by the formula:
    • Vs/Vp = Ns/Np, where:
      • Vs: Voltage across the secondary coil.
      • Vp: Voltage across the primary coil.
      • Ns: Number of turns in the secondary coil.
      • Np: Number of turns in the primary coil.
  • The power input and output ideally satisfy the relation Pin = Pout (assuming no losses).

Types of Transformers

  • Step-up Transformer: Increases voltage from the primary to the secondary coil (Ns > Np).
  • Step-down Transformer: Decreases voltage from the primary to the secondary coil (Ns < Np).

Construction of a Transformer

  • Consists of two windings: primary coil and secondary coil.
  • The coils are wound on a magnetic core made of laminated sheets to reduce energy loss.
  • Uses high-quality insulation to prevent short circuits.

Efficiency of a Transformer

  • The efficiency of a transformer is defined as:
  • Efficiency = (Output Power / Input Power) × 100%
  • Real transformers are not 100% efficient due to energy losses.

Energy Losses in Transformers

  • Core Loss (Hysteresis and Eddy Current Loss): Losses in the magnetic core due to alternating flux.
  • Copper Loss: Heat loss due to resistance in the windings.
  • Leakage Flux: Some magnetic flux does not link with the secondary coil.
  • Dielectric Loss: Loss due to insulation resistance.

Applications of Transformers

  • Power Transmission: Step-up transformers increase voltage for transmission, reducing energy loss.
  • Power Distribution: Step-down transformers reduce voltage for safe household or industrial use.
  • Electrical Devices: Used in chargers, adapters, and power supplies.
  • Isolation Transformers: Provide electrical isolation between circuits for safety.
  • Testing Equipment: Used in laboratories to test circuits at different voltage levels.

Conclusion

  • A transformer is a crucial device in modern electrical systems, enabling efficient power transmission and distribution.
  • Understanding its working and applications is essential for mastering concepts in electromagnetic induction and competitive exams.

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Questions

  1. What is the working principle of a transformer?
  2. In a transformer, what is the role of the primary coil?
  3. What type of current is required for a transformer to operate?
  4. What is the purpose of the core in a transformer?
  5. How is the voltage ratio between primary and secondary coils determined in a transformer?
  6. What type of transformer increases voltage?
  7. What type of transformer decreases voltage?
  8. What is the efficiency of an ideal transformer?
  9. What is the role of insulation in a transformer?
  10. What kind of loss occurs due to the resistance of transformer windings?
  11. What type of loss occurs due to eddy currents in the transformer core?
  12. What material is commonly used for transformer cores?
  13. How does a step-up transformer affect current in the secondary coil?
  14. What is the purpose of the laminated core in a transformer?
  15. What does the mutual induction process in a transformer involve?
  16. Which device uses a step-up transformer?
  17. Which device uses a step-down transformer?
  18. What happens to the frequency of the current in a transformer?
  19. What limits the efficiency of a transformer in practical applications?
  20. How can hysteresis losses in a transformer be reduced?
  21. What is the typical efficiency range of a transformer?
  22. How does a transformer transfer electrical energy?
  23. What happens to the magnetic flux in the core of a transformer under load?
  24. Which law of physics governs the operation of a transformer?
  25. What is the role of an isolation transformer?
  26. Why is high voltage used in power transmission through transformers?
  27. What happens to the current in a transformer with a higher secondary voltage?
  28. What type of transformer is used in distribution systems?
  29. What is the power output of an ideal transformer compared to its input?
  30. What type of transformer can adjust voltage within a small range?
  31. How can eddy current losses in a transformer be minimized?
  32. What determines the secondary voltage in a transformer?
  33. What is the main function of a transformer in an electrical circuit?
  34. What happens to the power in an ideal transformer?
  35. What type of transformer is used in a welding machine?
  36. Why are transformers rated in kVA instead of kW?
  37. What is the purpose of oil in some transformers?