Electricity

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Created by: Kirsten Reading
Created on: 24-04-13 22:09

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ELECTRICITY
- Static
  - When materials are rubbed against each other...
    - Electrons move from one material to another
    - Material that loses electrons becomes +
    - Material that gains electrons becomes -
    - Equal but opposite charges in each material
  - Only negative charges move
  - Opposite charges attract
  - Same charges repel
- Circuits
  - Current
    - Ammeter
      - Series
    - = charge / time
    - Rate of flow of charge
    - More cells = bigger p.d. = more current
  - Volts
    - Voltmeter
      - Parallell
    - = work done / charge
    - Work done
    - Total p.d. = sum of p.d.
  - Series
    - Current is the same
    - P.d. is shared
    - Resistance adds up
  - Parrallel
    - Current is shared
    - P.d. is the same
- Resistance
  - = p.d. / current
  - Moving electrons collide with ions in the metal
    - Makes it more difficult for current to flow (resistance)
    - Hotter ions = vibrate more = more collisions with electrons = greater resistance
- Household
  - UK mains = 230V = 50Hz
  - DIRECT CURRENT - current flows in one direction
  - ALTERNATING CURRENT - current constantly changes direction
  - Plugs & Cables
    - Neutral (blue)
    - Live (brown)
    - Earth (green/yellow)
    - Plastic, brass pins, fuse, cable grip
  - Too much current - fuse breaks
    - Protects wiring and appliance
      - Piece of wire heats up & melts easily
    - Circuit breakers = quicker, don't need replacing
  - Earthing
    - Safe route for current if live wire touches casing
      - Strong current = low resistance = breaks fuse