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Homework Help: Electromagnetic field

  1. Apr 4, 2007 #1
    1. The problem statement, all variables and given/known data

    A 1400 nF capacitor with circular parallel plates 1.0 cm in diameter is accumulating charge at the rate of 25.0 mC/s at some instant in time. What will be the magnitude of the induced magnetic field 9.0 cm radially outward from the center of the plates?
    What will be the magnitude of the field after the capacitor is fully charged?

    2. Relevant equations

    Obviously i'm a little confused, but I believe the general equation is B=mevE where B is magnetic field, e is c^2/Nxm^2, m is Nxs^2/C^2...on second, thought, i'm very confused.
    another possibility is B=(mu) initial x I/ 2 pi r

    3. The attempt at a solution

    Last edited: Apr 4, 2007
  2. jcsd
  3. Apr 4, 2007 #2


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    Science Advisor
    Gold Member

    Well some of your comments are on the right track. First you need to calculate the current, given the charge per second. Then use that current in your secon equation (often called the law of Biot and Savart).

    However, don't forget to look at the units!! You can't just plug in 25 without making use of its units milli-Coulomb.
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