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For more information, please see full course syllabus of AP Physics B
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Lecture Comments (1)

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Post by Jose Elenes on January 20, 2014

how does the faradays ice pail electric field sketch look like?

Faraday's Law

  • Magnetic flux: if a loop, of area A, sits in a uniform magnetic field B, a magnetic flux exists through the loop. If the loop plane is perpendicular to B, the flux is equal to BA. If the normal to the plane of the loop makes an angle theta with B, then the flux is given by BAcos(theta).
  • Faraday’s law: If the magnetic flux through a loop changes with time, an emf is induced in the loop. The value of the emf is minus the rate of change of the magnetic flux.
  • Lenz’s law: this law determines the direction of the current induced in a loop due to the changing magnetic flux. It states that the induced current has a direction so as to oppose the change of flux that induces the current. For example, if B is in the positive z direction and is increasing with time, and the loop is in the x-y plane, then the induced current will be clockwise, so as to produce a magnetic field in the negative z direction.

Faraday's Law

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Faraday's Law 0:57
    • Coil Connected to Battery With Switch
    • Closed Switch Ammeter Reads Current
    • Current in First Coil Drops to Zero
    • Change in Flux Generates Current
    • Induced EMF
  • Example 13:45
    • Coil Has N Turns
    • Connecting the Ends of Wire to Resistance
    • Total Flux
  • Motional EMF Revisited 25:04
    • Rod Moving in a Magnetic Field
    • Magnetic Force Pushes Electrons
    • Magnetic Field is Perpendicular to Area
    • Flux in Loop
  • Lenz's Law 40:03
    • Magnetic Field into Page
    • Current Induced by Increased Flux
    • Current Induced to Oppose Change in Flux
    • Flux is Increasing, Opposing Created Magnetic Field In Opposite Direction
  • Extra Example 1: Loop of Wire in Magnetic Field
  • Extra Example 2: Coil in Square
  • Extra Example 3: Decreasing Magnetic Field