AC Production and Transmission

AC Production and Transmission

AC Production

Alternating Current (AC)

  • An Alternating Current (AC) changes direction regularly and periodically.
  • In the UK, the standard AC frequency is 50Hz, meaning the current changes direction 50 times every second.
  • AC can be represented graphically as a sine wave.
  • AC is produced by generators in power stations. These use the principle of electromagnetic induction.

Electromagnetic Induction

  • Electromagnetic Induction is the process of generating an electric current from a changing magnetic field.
  • Changes in magnetic field can be caused by relative motion between a coil and a magnet.
  • This is where a voltage, or Electromotive Force (EMF), is induced which causes current to flow.


  • Generators convert mechanical energy into electrical energy.
  • They work on the principle of electromagnetic induction, where a coil is rotated within a magnetic field or vice versa.
  • The coil’s motion within the magnetic field induces a voltage, which leads to the flow of AC.

AC Transmission


  • A Transformer is used to change the voltage of an electric current.
  • Transformers make long-distance transmission of AC more efficient, by stepping up the voltage to reduce heat loss in the cables.
  • They can step up or step down voltage, depending on requirements at different stages of power transmission.

Advantages of AC Transmission

  • AC can be easily converted between different voltage levels using transformers, making it more suitable for long distance transmission.
  • Transmission at high voltage and low current minimises energy loss due to the heating effect.
  • Electricity grids worldwide use AC because it is safer to transfer over longer distances.

Power Grids

  • Most Power Grids use a mixture of overhead and underground cables to distribute electricity.
  • Power is carried at high voltages from power stations and is stepped down to safe, usable levels for homes and businesses.
  • Transformers are utilised at various points in the grid to ensure efficient transmission and distribution.
  • Electrical energy can be lost in the process due to resistance in the wires, causing them to warm up. This is why high voltage is used for transmission.