2.2.5 Mains Electricity

• Mains electricity

  The standard electrical power supply delivered to homes and businesses through the electrical grid
• Characteristics of Mains Electricity

  • Voltage
  • Frequency
  • AC vs. DC
• In the UK, the mains electricity voltage is typically 230 volts (V)
• The standard frequency of mains electricity in the UK is 50 Hertz (Hz)
• AC

  Alternating current, meaning the direction of the current periodically reverses
• DC

  Direct current, which flows in a single direction
• Components of Mains Electricity

  • Live Wire
  • Neutral Wire
  • Earth Wire
• Live Wire

  • Color Code: Brown (in the UK)
  • Function: Carries the current to the appliance
• Neutral Wire

  • Color Code: Blue (in the UK)
  • Function: Completes the circuit by carrying the current away from the appliance
• Earth Wire

  • Color Code: Green and Yellow stripes (in the UK)
  • Function: Provides safety by directing any fault current away from the appliance
• Fuse

  Protects the circuit by melting and breaking the circuit if the current exceeds a certain level
• Circuit Breaker

  Automatically cuts off the supply when there is a fault
• Earth Leakage Circuit Breaker (ELCB)


  Detects earth faults and cuts off the electricity supply to prevent electric shock
• Electrical power


  The rate at which energy is transferred by an electric circuit, measured in watts (W)
• Energy Consumption

  The amount of energy used by an appliance over time
• Energy is measured in kilowatt-hours (kWh)
• A 1 kW heater running for 2 hours uses 2 kWh of energy
• Electrical Appliances

  • Designed to operate at mains voltage and frequency
  • Include devices like refrigerators, toasters, and televisions
• Plug Design

  • Designed with safety features, including fuses and insulating materials
• Wiring

  • Electrical wiring in homes is designed to handle the standard mains voltage and is installed according to safety regulations
• Familiarity with color codes for wires is crucial for understanding and working with electrical systems
• Understanding mains electricity is vital for grasping how electrical systems work, ensuring safety, and managing energy use effectively