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Homework Help: Multistep problem (help on how to do, do not give answers)

  1. Feb 6, 2009 #1
    1. The problem statement, all variables and given/known data
    A 80 m Copper wire 1mm in diameter is joined end to end with a 49.0 m iron wire of the same diameter. The current in each is 2 A. (a) Find the current density in each wire (b) Find the electric field in each wire (c) Find the potential difference in each wire (d) Find the equivalent resistance which would carry the same 2A at a potential difference equal to the sum of that across the two. In the answer box,first write values for Cu then a comma(,) and then value for Fe

    2. Relevant equations

    3. The attempt at a solution
    This is a practice assignment to prep us for our test in weeks, i have an idea how to do these types of problems but this one adds a bunch of mini steps (like for part a, i know that current density is current divided by area, but he's never given a 3d example; we just took the area of a circle, etc., so would i use the entire surface area of the cylinder or just the circle base) and that's where i get confused. could someone, not give me the answers to each step (because i can do bio/chem simply, but i gotta learn physics... its just too abstract), but help me out on how to do them to where i can work them out and get the feel of how to approach these kinds.
  2. jcsd
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