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Homework Help: Magnetic Field Inside a Charging Capacitor

  1. Oct 20, 2013 #1
    1. The problem statement, all variables and given/known data
    A 10-cm-diameter parallel-plate capacitor has a 1.0 mm spacing. The electric field between the plates is increasing at the rate 1.4×106V/m*s.
    What is the magnetic field strength 2.7cm from the axis?

    2. Relevant equations

    [itex]\oint[/itex]B*ds=[itex]\mu[/itex][itex]\epsilon[/itex]dE(t)/dt*A
    B=([itex]\mu[/itex][itex]\epsilon[/itex]dE(t)/dt*A)/(2[itex]\pi[/itex]r)

    B=([itex]\mu[/itex]Id)/(2[itex]\pi[/itex]R2)*r
    3. The attempt at a solution
    I tried using the first equation:
    8.85E-12*4[itex]\pi[/itex]E-7*1.4E6*[itex]\pi[/itex](0.05)2/(2[itex]\pi[/itex]*0.027)=
    7.2E-13T which is wrong
     
  2. jcsd
  3. Oct 20, 2013 #2

    mfb

    User Avatar
    2017 Award

    Staff: Mentor

    "A" should be the area your integral encloses, not the total area of the capacitor.
     
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