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  • P2b
    • fuses and earthing
      • a fault allows live wire to touch metal case, a big current flows out through earth wire, a big surge in current blows the fuse, the device is isolated from the earth wire
    • atomic  structure
      • Rutherford and Marsden
        • fired a beam of alpha particles at some gold foil
        • expected to see slightly deflected alpha particles by the electrons
        • most went straight through, some came straight back, some deflected
          • most of mass concentrated in tiny nucleus, nucleus must be positively charged, most of atom must be empty space
    • background radiation
      • dumped nuclear waste and nuclear weapons would add to this
      • food
    • half life
      • always some background radiation, radioactivity will never fall to 0
    • uses of radiation
      • smoke detectors use alpha
      • tracers in medicine always use short life beta or gamma
      • radiotherapy uses gamma
      • sterilisation of food and surgical instruments uses gamma
    • nuclear fission  and fusion
      • fission forms lighter elements, uses uranium or plutonium (not hydrogen), radioactive waste is formed, and reactors already exist, all unlike fusion
    • life cycle of stars
      • gas and dust in orbit around a newly formed star may clump together to form masses which merge together to form planet
      • stars become red giants because the hydrogen fuel begins to run out
        • red giants are red because the surface cools


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