topic 11

• Atoms


  Basic unit of matter
• Neucleus


  the positively charged central core of an atom, containing protons and neutrons.
• Protons


  particles in the nucleus that have a positive charge.
• Neutrons


  particles of the nucleus that have no charge
• Electrons


  Negatively charged subatomic particles which are in orbit around he nucleus.
• Positive Ions


  Atoms which have lost one or more electrons so that they are positively charged.
• Negative ions


  Atoms which have gained one or more electrons so that they are negatively charged.
• Electrical energy


  The energy associated with electric charges.
• Electrostatic charges


  non-moving electric charges
• Conductors


  materials that allow electric charges to move through them easily.
• Metals


  materials that are good conductors of electricity.
• Insulators


  materials that prevent electric charges from moving through them easily.
• Plastics


  Materials the make good insulators of electricity.
• Friction


  A force that opposes motion between two surfaces that are in contact and can cause electrons to be transferred.
• Charged


  Describes an object whose net charge is not zero.
• Negatively charged


  When a material has more electrons than Protons.

  ie it has gained some electrons.
• Positively charged


  When a material has more protons than electrons

  ie it has lost some electrons.
• Neutrally charged or Not charged


  Particles which have the same number of electrons and protons so that the overall charge is zero.
• Attraction


  The force between objects with different charges which pulls them together.
• Repulsion


  The force between objects with same charge which pushes them apart.
• Gold leaf electroscope


  A piece of equipment used to detect charge
• Charging (3 methods)


  When an object gains static electricity by

  - friction. (Rubbing two surfaces）

  - conduction （contact allows electrons to flow)

  - induction (without contact)
• Discharging ( 3 methods)

  When an object loses static electricity by

  - conduction （contact allows electrons to flow)

  - Sparks (air conducts the charge away)

  - earthing/grounding (the object is connected to earth）
• Earthing （ also called grounding)


  When electricity flows between a source of current and the ground
• Dangers


  - Explosions due to sparks igniting explosive materials

  - Fires dues to sparks igniting Flammable materials

  - Disruption of electronic devices eg pace makers.

  - Attracting dust to sterile surfaces
• Nuisances


  - Electrical shocks when touching objects.

  - Hairs standing on end.

  - Jumpers and clothes sticking together.
• Uses of Static electicity

  - Photocopiers

  - Inkjet Printers

  - Paint sprayer.

  - Electrostatic precipitators (smoke cleaners)
• Triboelectric series


  The materials at the top lose electrons easily and the ones at the bottom gain electrons easily.

  Skin, glass, hair, nylon, wool, silk, cotton, rubber, polyester, polythene and PVC.
• Plastic or glass gains +ve charge

  (by losing electrons)

  when rubbed with silk

  (So the silk gains electrons and becomes -ve charged)
• Polythene or ebonite gains -ve charge

  (by gaining electrons)


  when rubbed with fur

  (So the fur loses electrons and becomes +ve charged)