P1.26-P1.27 Generating and Transmitting Electricity

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  • Generating and Transmitting Electricity
    • Electromagnetic induction
      • when a piece of wire is moved in a magnetic field
        • creating an induced current
          • Increasing the induced current
            • more turns on the coil of wire
            • iron core
            • stronger magnet
            • move wire faster
          • changing the direction of an induced current
            • change the direction of the movement of the wire
            • change the direction of the movement of the magnetic field
      • Bicycle dynamos
        • a magnet spins inside a coil of wire, inducing a current, powering the bike's lights
          • also used for wind up radios and torches
        • DC current
          • flows in one direction
      • electromagnets are used in  generators because they are more powerful
    • Generators
      • permanent magnets produce a magnetic field
        • an iron core spins round and round inside the magnetic field, inducing a current
          • current flows through spinning coil of wire around core
            • current flows through spinning slip rings
              • current flows through carbon brushes and the AC current can be used
    • National Grid
  • Power station
    • step up transformer
      • transmission lines
        • step down transformers
          • homes, shops and offices
          • factories
          • to decrease voltage for safety
      • to increase voltage, therefore decreasing current, decreasing heat loss, improving efficiency
  • 25 000 V
  • Transformers
    • two coils of wire around an iron core
    • electricity is supplied to the primary coil and obtained from the secondary coil
    • change the size of an alternating voltage
    • step up transformers increase voltage and decrease current
      • more turns of wire on secondary coil
    • step down transformers decrease voltage and increase current
      • more turns of wire on primary coil


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