# Canceling Magnetic Field between two wires using an external force

## Homework Statement

Suppose that I1 = I2 = 20 A; currents are running opposite each other, and that the separation between the wires is 0.019 m. By applying an external magnetic field (created by a source other than the wires) it is possible to cancel the magnetic field at the position of each of the wires. This external field must point along the vertical direction. What is the magnitude of the external field?

## Homework Equations

B= [(permeability of free space) times (current)]/ [(2 (pie) r)]
F(from wire 1 to 2)= I2 [(permeability of free space)I1]/[2 pie r] times L
Permeability of free space is 4 pie times 10-7 Ttimes m/A

## The Attempt at a Solution

Working through this a plugged in current and separation between wires into the equation to find B. I got .084 Telsa. I found out this was the wrong answer and thought doubling it would get me the right answer, but it didn't. I wasn't given a radius for the wire so I don't know what to do. Can anyone help me?

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