P4.9 How Transformers Work

• What is the primary function of transformers in the national grid?

  To increase or decrease voltage
• Why is electricity generated at huge power stations spread out across the UK?

  To ensure efficient distribution of electricity
• What voltage do step-up transformers increase electricity to?

  Around 400,000 volts
• What is the purpose of increasing voltage in the national grid?

  To minimize energy losses during transmission
• What voltage do step-down transformers decrease electricity to?

  Around 230 volts
• What is the role of the iron core in a transformer?

  To connect the primary and secondary coils
• How does an alternating potential difference affect the primary coil?

  It generates an alternating magnetic field
• What happens to the magnetic field in the iron core when an alternating magnetic field is applied?

  It induces an alternating magnetic field
• What does the induced magnetic field in the iron core do?

  It induces a potential difference across the secondary coil
• Why can't electricity pass directly from the primary to the secondary coil?

  Because the wires are insulated in plastic
• If a step-up transformer has twice as many turns in the secondary coil, what happens to the voltage?

  The voltage is doubled
• What is the difference between a step-up and a step-down transformer?

  Step-up increases voltage; step-down decreases it
• What are the key components of a transformer and their functions?

  • Primary coil: Receives input voltage
  • Secondary coil: Delivers output voltage
  • Iron core: Connects coils and enhances magnetic field
• What are the steps involved in how a transformer operates?

  1. Alternating potential difference applied to primary coil
  2. Current flows, generating an alternating magnetic field
  3. Magnetic field induces an alternating field in the iron core
  4. Iron core induces potential difference in the secondary coil
  5. Current flows in the secondary coil
• What are the implications of using transformers in the national grid?

  • Efficient long-distance electricity transmission
  • Reduced energy losses
  • Safe voltage levels for consumer use
• Do transformers work with alternating or direct electrical supplies?


  Alternating electrical supplies (alternating voltage/current)
• What do transformers do?


  Transformers change the voltage and current of an alternating current.
• What does a step-down transformer do?


  A step-down transformer decreases the voltage and increases the current.
• Where could a step-down transformer be used?


  A step down transformer could be used before electricity enters a home, to ensure the voltage is low enough to be safe.
• What does a step-up transformer do?


  A step-up transformer increases the voltage and decreases the current.
• Where could a step-up transformer be used?


  A step-up transformer could be used as electricity leaves a power station and enters the national grid.
• Why is it important to use a step-up transformer before electricity is transmitted across the national grid?


  It is important to have very high voltage and low current to minimise energy loss during transmission.
• How do transformers work?


  1. When supplied with an alternating current, the primary coil will generate an alternating magnetic field.
  2. This induces an alternating magnetic field in the iron core.
  3. This, in turn, induces an alternating voltage in the secondary coil, which- if the circuit is complete- will lead to an alternating current.