Electricity

• Electricity

  A convenient form of energy that is transferred from place to place as an electric current
• Electrical conductors

  • Materials that conduct an electric current
  • All metals are good conductors
• Electrical insulators

  • Materials that do not conduct an electric current
  • Include plastic, wood, glass, rubber and card
• Metals

  Good conductors because they contain delocalised electrons that carry electrical charge along the metal
• Insulating materials


  Do not contain delocalised electrons
• Electricity is potentially dangerous
• Electrical devices must be handled with care
• Connecting an electrical appliance

  1. Appliance is connected to a plug

  2. Plug fits into a socket, which provides electricity
• Things electrical users should not do

  • Poke objects into sockets
  • Use appliances with damaged plugs
  • Handle appliances with wet hands
• Electrical appliances with metal bodies

  • Connected to an earth wire that provides a pathway for current in the event of wires coming loose and touching the metal body
  • Protects the user from severe electric shock
• Electrical appliances with plastic bodies

  • Do not require an earth wire and are said to be double insulated
• Mains electricity is too dangerous for use in laboratory experiments
• Cell

  A means of providing a small and safe amount of energy
• Battery


  Formed when two or more cells are joined together
• Cell terminals


  Positive (+) and negative (-)
• There is a difference in potential between the terminals of a cell
• Connecting cells to form a battery

  Cells must be pointing in the same direction, with the positive terminal of one connected to the negative terminal of another
• Conventional current


  Flows from the positive terminal of a cell or battery through the circuit to the negative terminal
• Electron flow


  Is in the opposite direction to the conventional current
• Complete circuit


  • Needed for an electric current to flow
  • Current stops if there is a break in the circuit
• Switch


  A device that can be used to turn a device on and off by completing or breaking the circuit
• Ammeter


  Used to measure electric current
• Current unit


  Ampere (A) or milliampere (mA), with 1000 mA in 1 A
• Circuit diagram


  A method of representing a circuit by a series of connected symbols, each representing a component
• Building a circuit from a diagram

  1. Identify the electrical components

  2. Determine how the components are connected together