Electromagnetic Induction and Transformers

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  • Created by: Lina
  • Created on: 09-04-14 16:53
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  • Electromagnetic Induction
    • The creation of p.d. across a component which is experiencing a change in magnetic field
      • An electric current will flow in the circuit if the component is part of a complete circuit
    • 1) Conductor moved in a magnetic field, e.g. a wire between 2 magnets
      • Or turning a magnet end to end in a coil+ spinning it
        • As you turn the magnet, the magnetic field through the coil changes-> induces the p.d.-> makes current flow in the wire
          • Turn the magnet through half a turn-> the direction of the magnetic field through the coil reverses-> the p.d. reverses-> current flows in the opposite direction around the coil
            • Keep turning the magnet in the same direction-> p.d. will keep reversing every half turn-> AC current
    • 2) Magnet is moved in a coil of wire
      • If the magnet is moved in the opposite direction-> the p.d. will be reversed
      • If the polarity of the magnet is reversed-> the p.d. is also reversed
      • Keep the coil/ magnet moving backwards+ forwards-> produce a p.d. that keeps swapping direction-> AC
    • Transformers
      • Use a soft iron core- easily magnetised
      • The coils are insulated, so that the current doesn't cut across either the iron core or adjacent turns of wire
      • The DC can't be used because it would be continually expanding+ collapsing-> no p.d. would be induced because you need a changing magnetic field
      • The primary coil produces a magnetic field which stays within the iron core+ passes to the secondary
        • Because of the AC, the field in the iron core is constantly changing direction
          • Felt by the secondary-> p.d. is induced

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