Magnetic field of wire

[Jethom18]

Homework Statement

A long straight wire lies along the z-axis and carries an 8A current in the +z direction. Find the magnetic field (magnitude and direction) produced at x = 0.4m, y = 0, z = .3m by a .7mm segment of wire centered at the origin.

Homework Equations

B = u(0)I / 2piR

The Attempt at a Solution

b = (4(pi)x10^-7) (8A) / (2pi (.7x10^-3) ==> 2.3 mT(tesla)

I think that's right, but I'm not sure where the magnitude and direction with the vectors come in. I'm assuming you subtract vector 1 from origin vector to leave .4i + .3k. Then do you take the magnitude and multiply it by b?

Thanks for any help.

 

[ideasrule]

You didn't use the right equation to find B. B = u(0)I / 2piR is for an infinitely long wire, but the question asks for the field produced by a finite wire segment.