P2.4 Mains Electricity Part 1

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  • Created by: Lauren
  • Created on: 20-05-13 18:46
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  • P2.4 Mains Electricity Part 1.
    • Mains electricity is useful but can be very dangerous.
    • Cells and batteries supply current that always passes in the same direction.
      • This is called direct current (d.c.).
    • An alternating current (a.c.) is one that is constantly changing direction.
      • Mains electricity is an a.c. supply.
      • The frequency of an alternating current is the number of cycles it passes through per second.
        • In the UK the mains frequency is 50 cycles per seond or 50 Hertz.
        • To measure the frequency of an a.c. supply, we measure the time period of the waves and put it into the formula: frequency = 1/time taken for 1 cycle.
    • The three-pin plug.
      • Most electrical appliances are connected to the mains using a cable and a three-pin plug.
      • The materials used for the plug and cable are designed to reduce risk of electrocution.
        • The inner cores of the wires are made of copper because it's an excellent conductor.
        • The outer layers of the wires are made from flexible plastic because it's a good insulator.
        • Wires comprise of either a two-core or three-core cable. The three-core carries the earth wire.
        • The pins of the plug are made from brass because it's a good conductor, strong and stiff.
        • The casing is made from plastic or rubber because both are good insulators.
      • The main content of a three-pin plug is...
        • A live wire (brown).
        • An earth wire (yellow and green).
        • A neutral wire (blue).
        • A cable grip.
        • A fuse.
        • Casing.

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