Force per unit length of wires-

[yankeekd25]

Homework Statement

Two wires have current both running in the positive x direction as shown in the diagram with I1 = 13.9 amps and I2 = 4.5 amps. They are separated by a distance of d = 4.7 meters. A third wire with I3 = 10 amps is placed somewhere between the two wires with current running in the positive x direction. How far above (in the positive y direction) above I1 should I3 be placed such that the force per unit length from both wires acting on I3 be equal to zero? Answer in meters.

The diagram is basically an x-y plane, with three wires going in the positive x direction.

-----------> I2
-----------> I3
|-----------> I1

Homework Equations

Force/ unit length= u0 I1 I2/ 2pi D

The Attempt at a Solution

I know that the force per unit length of wire 1 must equal wire 2 so there is no net force per unit length, but I'm not exactly sure how to do this. How do I write an equation that allows us to do this to find the distance from I3 to I1?

Thank you.

 

[yankeekd25]

Can anyone please help me out? THanks