Mains electricity

• The three wires in the three core cable are made of copper, which is a good conductor of electricity
• The coatings of the wires are made of plastic, which does not conduct electricity
• Live wire:

  • Carries electricity with a potential difference of 230 volts from the electricity generators
  • Connected to a fuse in the plug
  • Can be extremely dangerous and fatal if touched, even if the switch is open
  • If touched, a current would flow through the person into the earth, leading to electrocution
• Neutral wire:

  • Completes the circuit
• Earth wire:

  • Connected to appliances with metal cases
  • Prevents electric shocks if the live wire comes loose and touches the metal case
  • Metal case is attached to the earth wire, which is connected into the ground with a metal rod
  • If the case becomes live, a huge current flows to the earth, the fuse melts, and shuts off the current to prevent electric shocks
• Wires in a circuit have low resistance, which is why they do not become warm easily
• Appliances like kettles need heating elements with high resistance to become warm
• Energy is transferred to elements, heating them up
• A 70 watt bulb is brighter than a 40 watt bulb because it transfers 70 joules of energy every second, which is 30 joules more than the 40 watt bulb
• Power is measured in joules per second or watts
• Electricity from mains shows a wave-like pattern due to alternating current generated at power stations
• Direct current is when current travels in a straight line, found in batteries and cells
• The three wires in the three-pin cable are:

  • Brown wire: Live wire carries a potential difference of around 230v and is connected to a fuse in the plug
  • Blue wire: Neutral wire, which completes the circuit with the live wire, has a potential difference of around 0v compared to the live wire
  • Green and yellow-striped wire: Earth wire, a safety wire

  
• Main electrical appliances plug into wall outlets and run on the electricity supplied by the grid

  
• Common electrical problem: surges, sudden increases in current
• Surges can occur when something changes in a circuit or due to a fault in the circuit or appliance
• Surges can damage appliances, cause fires, and electric shocks
• Double insulation: Entire appliance covered in plastic casing

  • No exposed metal parts to touch
  • Prevents electric shocks as plastic doesn't conduct electricity
  • Appliances with double insulation usually don't need an earth wire
• Hazards of mains electricity:

  • High voltage supplied by mains
  • Frayed cables
  • Damaged plugs
  • Metal objects in sockets
  • Long cables with high resistance that can heat up
  • Water around electricity
  • Overloaded plugs that may get hot and melt
• Safety features on UK plugs:

  • Brown lead is the live lead, connected to the fuse
  • Fuse melts if a larger current passes through, protecting from fires
  • Green and yellow lead is the earth wire, connected underground to Earth
  • Blue lead is the neutral pin
  • All leads should be double insulated
  • Cord grip should grip onto the outer layer of insulation
• Inside an appliance:

  • Brown lead and blue lead (live and neutral) power the appliance
  • Green and yellow lead (earth) is connected to the metal outer casing
  • If a fault occurs and the live lead touches the metal casing, the current passes through the earth lead back to the supply, blowing the fuse and rendering the appliance safe
• Fuses in the UK come in three main varieties: 3, 5, and 13 amps

  • Fuses melt if a larger current flows through, preventing fires and overheating of cables or appliances