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AP Physics Chp 22

AP Physics Chp 22. Electromagnetic Induction If a magnetic field changes near a conductor then an emf is induced which induces a current in the conductor. Move a magnet Move a coil Changing area of a coil also induces an emf.

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AP Physics Chp 22

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  1. AP Physics Chp 22

  2. Electromagnetic Induction • If a magnetic field changes near a conductor then an emf is induced which induces a current in the conductor

  3. Move a magnet • Move a coil • Changing area of a coil also induces an emf

  4. Moving a solid conductor in a constant magnetic field also induces an emf and current • ε= vBL all perpendicular

  5. Magnetic Flux • ε= B∆A / ∆t = ∆ф / ∆t ф = BA mag. Flux • unit is Tm2 = weber Wb • ф = BA cos ф angle between A and B

  6. Faraday’s Law • GFCI and AFCI

  7. Lenz’s Law • An induced emf results from a changing magnetic flux has a polarity that leads to an induced current with a direction so the induced magnetic field opposes the original magnetic flux

  8. Generators

  9. Countertorque • Back (counter) emf • V-ε = IR

  10. Transformers • One coil with a current causes a magnetic field in an iron core. This magnetic field induces a current in a second coil.

  11. Power remains constant in a transformer • P=IV

  12. What ratio of coils in needed in the transformer that has an input of 120V and needs an output of 24V? • If it uses 4.5 A of input current what is the output current?

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