Magnetic Field with three parallel wires

  1. 1. The problem statement, all variables and given/known data
    Three long, straight wires are carrying currents that have
    the same magnitude. In C the current is opposite to that
    in A and B. The wires are equally spaced. Each wire experiences a net force due to the other two wires. Which
    wire experiences a net force that has the greatest magnitude?

    A =====>====
    B=====>====
    C=====<====

    2. Relevant equations
    FAB = μ°I1 I2 / 2∏d


    3. The attempt at a solution
    It says that the answer is B because 2I squared / d is the net force on B. But the way I am doing it is -I^2/d + I^2/d = 0, hence the net forces cancel out and the force on B is zero. I don't understand how it is 2I^2/d. Please help.
     
  2. jcsd
  3. Hi rikinmathur! Welcome to pf! :smile:

    What are the direction of forces on wire B due to the other two wires?
     
  4. Hey rikinmathur, just think in terms of charges, maybe this is easier for you: A and B are positively charged (in a magnetic sense) and C is negative. So, which wire-pairs will experience an attractive and which a repulsive force?
     
Know someone interested in this topic? Share a link to this question via email, Google+, Twitter, or Facebook

Have something to add?