1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Magnetic field of 2 infinite wires.

  1. Nov 6, 2011 #1
    1. The problem statement, all variables and given/known data
    Two thin, long wires situated in y = -a and y = a carrying two equal in magnitude and opposite running currents I.
    Find the field strength in therms of y.
    Find the average Field strength in a region -b to b, where 0 is between the 2 points.

    2. Relevant equations
    Amperes law.

    3. The attempt at a solution
    I find via. Amperes' law, that the field of the wire in -a (current running down) has the magnitude:
    [itex] B(y) = \dfrac{\mu_0 I}{2\pi r_1}[/itex]
    Where r1 is the distance from the wire, now i find that r1 = a-y.
    The field from the other is the same with the distance r2 instead of r1. r2 = a-y too so the field is zero and the average is of course also 0, and that is annoying. What have i done wrong.
    Last edited by a moderator: Nov 6, 2011
  2. jcsd
  3. Nov 6, 2011 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Better check if, for the downgoing wire, r1 = a - y.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook