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Homework Help: Magnetic Field question

  1. Feb 23, 2010 #1
    1. The problem statement, all variables and given/known data

    This is a two part question I just want to check I'm on the right track - it just seems too easy to be worth the marks they're given so apologies now if I'm stating the obvious:

    a) Write down an equation for the magnitude B of the magnetic field at a distance D away in a vacuum from an infinitely long wire carrying a current i.

    b) Find the magnitude and direction of the magnetic field at the point O located at a distance D=10cm form a wire carrying a current i = 1.0A directed into the page.

    3. The attempt at a solution

    For a) I've got B(D)= (μ_0 i)/2πD

    Where μ_0 is the permeability of free space constant at 4π x 10^-7 T m A-1

    for b) I've just put the figures into the above equation, giving:

    B(D) = (4 x 3.14 x 10^-7) x 1A / (2 x 3.14) x 0.1m

    That just seems far too easy - what am I missing? Many thanks
  2. jcsd
  3. Feb 23, 2010 #2


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    Science Advisor
    Homework Helper
    Gold Member

    You are missing that this is indeed an easy problem. :wink:

    I hope you got the direction right in the second part.
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