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Homework Help: Magnitude of Magnetic Field

  1. Jan 26, 2005 #1
    I understand that it needs to relate to the following equation but that is it. [tex]B=\frac{\mu_{0} I}{2\Pi r}[/tex]

    I am unsure how to derive an answer for this, I am drawing a blank on solving this. Can anyone give me any helpful hints?
     
    Last edited: Jan 26, 2005
  2. jcsd
  3. Jan 26, 2005 #2
    what is the direction of the current???? post the whole question pls....
     
  4. Jan 26, 2005 #3
    That is the full question, the current is running through a hollow cylinder. From how I understand the current is flowing through direction of the hieght of the cylinder.
     
  5. Jan 26, 2005 #4
    find the [itex] \ver{A} [/itex] first, then B
     
  6. Jan 26, 2005 #5
    [tex]\oint{\vec{B}\vec{dl}}=\mu_0\int{\int_S{j}}ds[/tex]
    and from this you can simply derive

    [tex]B(r)2\pi r=\mu_0 j \cdot \pi(r^2-a^2)[/tex]

    where
    [tex]j=\frac{I}{\pi (b^2-a^2)}[/tex].
     
  7. Jan 26, 2005 #6
    Thanks to both of you. Clive you pointed out a part in which I made an error in my thinking of my previous answer. Appreciate the help.
     
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