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Homework Help: Force on wire due to current

  1. Jan 15, 2007 #1
    1. The problem statement, all variables and given/known data
    hi,im a bit confused by the following question.i think i have a fairly good idea of most of the solution but the actual wording of the question is stil throwing me.

    Q: 3 parallel wires,arranged in the form of an equilateral triangle,of side length 10cm,each carry a current of 50 A in the same direction.Calculate the force on any one wire due to the other two.

    2. Relevant equations
    I used the equation F= 2*10^-7(I1)(I2)/d
    and arranged wires as follows: *

    b* c*

    with wires going into page.

    3. The attempt at a solution
    i calculated the force on the top wire,a, due to b and c:
    F=2*10^-7(50)(50)/0.1 = 5.0*10^-3 N in each case,along the line joining a to b and a to c

    so this force F is attractive as the currents are in the same direction,yes?
    what i am wondering is if i have to calculate the resultant force on a,that is,use for eg the parallelogram rule to find the resultant force, which would point in the direction straight down,or can i simply leave the ans. as is??

    is there some sort of convention for expressing this direction or can i just say in the direction indicated on a diagram?

    i used the cosine rule and found that the resultant force is (3^1/2)(5*10^-3)N in the direction pointing straight down so that the vector would bisect bc as shown in diagram,does this make sense?
    thanks steve:rofl:
  2. jcsd
  3. Jan 15, 2007 #2
    ok that didnt work out,wires are meant to look like this:


    b* ............. c*

    ignore dots
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