Mains electricity Energy stores and systems


  • Most electrical appliances are connected to the mains using three-core cable.

The insulation covering each wire is colour coded for easy identification: live wire – brown

neutral wire – blue

earth wire – green and yellow stripes.

The live wire carries the alternating potential difference from the supply. The neutral wire completes the circuit. The earth wire is a safety wire to stop the appliance becoming live.

The potential difference between the live wire and earth (0 V) is about 230 V. The neutral wire is at, or close to, earth potential (0 V). The earth wire is at 0 V, it only carries a current if there is a fault.

Students should be able to explain:

  • that a live wire may be dangerous even when a switch in the mains circuit is open
  • the dangers of providing any connection between the live wire and earth.

WS 1.5 -Evaluate risks both in practical science and the wider societal context, including perception of risk in relation to data and consequences.

Quiz Lesson Guide

The 3 pin plug.mp4

3 pin PLUG

Quiz followed by Practical

Using quiz teams first before teaching to build resiliance

copy answers down in books when going through the answers


Practical :


  • Mains cord
  • Plug kits
  • wire strippers

Students create plugs for testing (when i finally get around to making a "PAT" tester)



  • Sharp cutters / Wires