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Homework Help: Help with ampere's law problem

  1. Sep 20, 2005 #1
    urgent help with ampere's law problem

    The problem reads as: Consider a hollow wire of inner radius a and outer radius b carrying a current I. Use Ampere's law to find the magnitude of the magnetic field B(r) as a function of distance r from the center of the wire.

    A) What is the current density in the wire?

    B) What is B(r) in the center hollow of the wire (r < a)?

    C) What is B(r) inside the metal part of the wire (a < r < b)?

    D) What is B(r) outside the wire (r > b)?

    HEre is the diagram:http://www.mustangmods.com/data/16002/untitled1.jpg

    Here is my work, i don't beleive i am doing it right for what it is asking.
  2. jcsd
  3. Sep 21, 2005 #2
    can anyone help?
  4. Sep 21, 2005 #3
    I wish I could help but magnetism isnt a strong point of mine. What I can tell you is this helped me alot last semester when I was taking the course.

    A) Current density is current per unit area, your unit area here is [itex] \pi (b^2-a^2) [/itex]

    B) In a solenoid there is a magnetic field between, but I'm not sure for a cylindrical wire.

    C) If there was a magnetic field inside the wire, it would affect the flow of current drastically. I doubt there is one.

    D) I'm quite confident there is a magnetic field outside.

    Again, don't bet on my answers, but I hope it gives you some pointers until someone else helps/
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