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: Finding magnitude of external field from two magnetic fields

  1. Nov 2, 2008 #1
    1. The problem statement, all variables and given/known data
    I was wondering how would you determine the magnitude an external field needed to cancel two magnetic fields in two wires? In this instance the currents of the two wires are in opposite directions...so I know there is a repulsion force.
    The currents in both wires are equal to 20 amps apiece
    The wires are parallel to each other and are 0.019meters apart.

    2. Relevant equations
    Going about this problem I thought this would be useful F(magnetic)= (Current)(Length)(Magnetic field)
    Also I thought this would be useful B= (4piE-7)(I) divided by (2pie X r)

    3. The attempt at a solution
    When I tried to plug in the values for B I got 0.000210526 for the magnetic field in one wire. If I double this I get 0.000421053 for the total force of repulsion. Would this be the correct way of approaching the problem.
  2. jcsd
  3. Nov 2, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    No, just go with the 0.00021. That's the magnetic field due to one wire, at the location of the other wire.
  4. Nov 2, 2008 #3
    Thank you. I really appreciate your help.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook