General

• Mains electricity

  a.c supply
• a.c.

  Alternating Current
• d.c.

  Direct Current
• Alternating current


  Current that continuously changes direction at a specific frequency
• Direct current

  One directional current flow
• Mains electricity in the UK is an a.c supply
• The frequency of the UK mains electricity supply is 50 Hz
• The voltage of the UK mains electricity supply is 230V
• Wires in cables connecting electrical appliances to the mains

  • Live wire
  • Neutral wire
  • Earth wire
• Earth wire insulation colour

  Green and Yellow Stripes
• When the Earth wire carries a current

  1. Under normal circumstances, no current flows through the Earth wire

  2. If a fault occurs in the appliance (such as a surge or the casing becoming live), current will flow to the ground
• The neutral wire is at 0 Volts
• The potential difference between the live and earth wires is 230 Volts
• Purpose of the neutral wire


  To complete the circuit by connecting the appliance back to the mains supply
• Where the Earth wire is connected for metal appliances

  1. Earth wire is connected to the metal casing of the appliance

  2. If live wire becomes loose and touches the casing, the current will flow through the Earth wire, preventing electrocution