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Faraday Induction

Faraday Induction. Animation – Faraday induction Magnetism and Induction Roadmap Magnetic Flux / Induced emf Lenz’s Law Examples of Lenz’s Law Examples of Induced emf Generators Transformers . Induction animation. https:// phet.colorado.edu/en/simulation/faradays-law.

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Faraday Induction

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  1. Faraday Induction Animation – Faraday induction Magnetism and Induction Roadmap Magnetic Flux / Induced emf Lenz’s Law Examples of Lenz’s Law Examples of Induced emf Generators Transformers
  2. Induction animation https://phet.colorado.edu/en/simulation/faradays-law
  3. Magnetism and Induction Flowchart Changing magnetic field creates current
  4. Magnetic flux and induced emf Magnetic Flux Area “vector” perpendicular to Area If area “vector” inline with field, area perpendicular to field Flux units weber of T-m2 Induced emf Units
  5. Direction of Induced Current Lenz’s Law Induced current will create magnetic field to oppose **change** that produced it Natural logic – things are not going to reinforce change that produces them – perpetual motion! Flux can change in 3 ways Area Orientation Magnetic Field
  6. Examples of Lenz’s Law – Fig 21-6 Fig 21-6 Flux down -> flux less down, change up, oppose change down, current CW Fig 21-7
  7. Examples of Lenz’s Law – Fig 21-9 Flux up -> flux less up, change down, oppose change up, current CCW Flux down -> flux less down, change up, oppose change down, current CW Flux down -> flux more down, change down, oppose change up, current CCW Magnetic field parallel to plane, no flux, no change in flux, no induced emf Flux zero, flux increasing to left, change to left, oppose change right, current CW
  8. Examples of Lenz’s Law – Fig 21-11 Flux down -> flux more down, change down, oppose change up, current CCW Flus down -> flux less down, change up, oppose change down, current CW No changing flux, no induced current. Flux down -> flux more down, change down, oppose change up, current CCW
  9. Calculation of induced emf (1) Know B = 0.6 T Width 5 cm 100 turns Time 0.1 s R = 100 ohms Find Emf, current (1.5 v 15 mA) Force required (.045 N) Work done by that force (2.25 mJ) Power, Work (22.5 mW, 2.25 mJ)
  10. Calculation of induced emf (2) Emf for single loop Emf for 100 loops Current clockwise by Lentz’s Law i
  11. Calculation of induced emf (3) Mechanical force to pull loop out to left Mechanical work to pull loop out Electrical power dissipated during pulling Electrical energy lost to pull loop out
  12. Other examples Change in B
  13. Other examples Change in A
  14. Other examples Change in A EMF from Flux (0.168V) EMF fromqvB Current (0.168V/27.5 ohm = 6.1 ma) Force (0.64 mN)
  15. Other examples Change in θ Generator
  16. Generator Φ = BA cos(ωt) ε = N dφ/dt ε = NBωA sin(ωt) Lentz’s Law Problems 20-25 Prob 20 (42 loops)
  17. Generator Φ = BA cos(ωt) ε = N dφ/dt ε = NBωA sin(ωt) Lentz’s Law Problems 20-25 Prob 20 (42 loops)
  18. Generator and Transformer Transformer On Primary Vp = NpΔΦ /Δt On Secondary Vs = NsΔΦ /Δt Since changing flux is same Vs/Vp = Ns/Np Power is conserved Is/Ip = Np/Ns Problems 30-
  19. Applications Electric generators Car alternators Transformers (why our power is AC) Hard drives, magnetic tapes Credit-card readers (why you always “swipe”)
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