Static electricity

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  • Created by: Clare
  • Created on: 25-03-13 20:52
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  • Static Electricity
    • Materials
      • Conductor
        • Materials that conduct electricity (usually metallic)
          • Copper, silver, gold
      • Insulator
        • Materials that do not conduct electricity
          • Rubber, glass, plastic, wood
    • Charges in an atom
      • Gain electrons= NEGATIVE
      • Atoms have no overall charge- protons and electrons are the same
      • Electrons in the shells can be transferred from place to place
    • Experiments
      • Polyethene and clear acetate rods can be charged by rubbing with a dry cloth
        • It then attracts dry pieces of paper
    • Forces
      • Attraction
      • Repulsion
      • Unlike charges attract, like charges repel
      • Metals
        • Electrons move freely so  when held near a charging object the OPPOSITE charge is induced
      • Uncharged objects
        • Electrons stay with atom but are weighted to one side and can still attract objects
    • Explanation
      • When rubbing 2 materials together, electrons are torn from one of the materials and transferred to the other
      • This changes the charges as the number of electrons are unbalanced so it causes attraction/ repulsion
    • Uses
      • Inkjet printers
        • Charging ink droplets so they can be directed in the required place  using charged plates
      • Photocopiers
        • Charged drum is exposed to light- reflected from the document
          • This discharges the drum except where there is black (doesn't reflect light)
            • Charged parts attract toner which is transferred onto paper and sealed with heat
      • Paint spraying
        • Paint droplets are given a static charge and the object to be painted is connected to a supply of the opposite charge
    • Dangers
      • Fueling tankers and aircraft
        • When fuelling static charge can build up and if there is a spark this will cause an explosion
          • Prevention: earthing straps and earthed metal benches
      • Electric shocks
        • Charges build up and shock to a person who touches the object


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