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  • Created by: Sophie
  • Created on: 05-05-13 11:21
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  • Transformers
    • Change the p.d- but only AC p.d
    • Primary and secondary coils, joined with an iron core
    • Step-up transformers
      • Increase voltage
      • More turns on the secondary coil than the primary coil
      • Magnetic field in the iron core
    • Step-down transformers
      • Decrease voltage
      • More turns in the primary coil than secondary
    • Work by electromagnetic induction
      • Primary coil produces a magnetic field which stays within the iron core. So neraly all of it passes through the secondary coil and hardly any is lost
        • Alternating current in the primary coil means the field in the iron core is constantly changing direction- its a changing magnetic field
          • Rapidly changing magnetic field felt by the secondary coil
            • Changing field induces an alternating potential difference across the secondary coil
              • Electromagnetic induction of a potential difference
              • Relative number of turns of the two coils deterines whether the p.d in the secondary coil is less or greater than the p.d in the primary
                • Step-up = p.d in secondary coil is larger than p.d of primary
                • Step-down transformer = the p.d across the secondary coil is less than the p.d of primary
    • DC wouldn't work as although there'd be a magnetic field in the core, it wouldn't be constantly changing so there'd be no induction in the secondary because you need a changing field to induce a p.d.
    • Iron ncore is for changing the magnetic field; no electricity flow through it.


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