SC 6.2

• Transformer

  • A device that changes the voltage of an alternating current
  • It is made up of a soft iron core with a coil of insulated wire on both sides of the core
  • When alternating current is flowing through the primary coil, a changing magnetic field is created continuously
  • This changing magnetic field induces an alternating voltage in the secondary coil
  • Primary coil - receive input voltage
  • Secondary coil - Produce output voltage
• The voltage produced (output voltage)can either increases or decreases, depends on:

  • The input voltage
  • The number of turns of the primary and secondary coil

  In a transformer, the voltage is larger on the side with more turns (wire coil)
• Types of transformer

  1. Step-up transformer
  2. Step-down transformer
• Step-up transformer

  • Input voltage is less than output voltage
  • Number of turns in the primary coil is less than that in secondary coil
  • E.g.
  • microwave oven
  • X-ray Machines
  • Neon Signs
• Step-down transformer

  • Input voltage is greater than output voltage
  • Number of turns in the primary coil is more than that in secondary coil
  • E.g.
  • Mobile Phone Chargers
  • Doorbell Systems
  • Electric Toys
• The function of transformers in the use of electricity in the home:

  • The electricity supply that reaches the house has a voltage of 240 V
  • Most electrical appliances in the home operate at a lower voltage
  • For example, a laptop uses 20 V out of a 240 V power supply so requires a step-down transformer to reduce the 240 V power supply