Magnetic Field Between Two Wires

[sgoeke]

Homework Statement

Two long parallel wires 20 cm apart carry currents of 5.0 A and 8.0 A in the same direction. Is there any point between the two wires where the magnetic field is zero.

Homework Equations

B=muI1I2/(2pir)

The Attempt at a Solution

I set the two B equations equal to each other to solve for r, but am stuck on what to do once I set them equal to each other: B1=B2, muI1/2pir = muI2/2pir

 

[Delphi51]

Welcome to PF!

I set the two B equations equal to each other to solve for r, but am stuck on what to do once I set them equal to each other: B1=B2, muI1/2pir = muI2/2pir

The trouble with that a point that is r from one wire is not going to be r from the other wire, unless the point is exactly half way between them. You pretty much need to express one of them as r and the other as .20 - r. This limits you to the plane of the two wires, but I think that is the unstated intent of the question. Anyway, you can now put in your known numbers and you'll have a nice equation with only the unknown r to solve for. Go for it!