# Homework Help: Two very long straight conducting wires problem

1. Jul 27, 2009

### cate25

1. The problem statement, all variables and given/known data

My picture won't upload but there is an x-y plane with point P at (5,4) and a vector shooting off from P in the SW direction. There are two wires pointing into the page (in the z plane) at (5,2) and (10,2).

Here is the actual problem:

Two very long straight conducting wires are perpendicular to the x-y plane. At point 'p', the magnetic field, shown on the figure below, is due to the currents in wires '1' and '2', with |B| = 4.782×10-4 T. Its components Bx= -4.470×10-4 T and By= -1.700×10-4 T.

I. Indicate the direction of the currents in the wires, +z (out of the page) or -z (into the page).

II. Calculate the magnitude of the current in wire2.
2. Relevant equations

III. Calculate the magnitude of the current in wire1.

3. The attempt at a solution

The current in wire 1 is in the -z direction and wire 2 is +z?
For the second part Bwire = (miu*I)/ (2*pi*R)

2. Jul 27, 2009

### tiny-tim

Welcome to PF!

Hi cate25! Welcome to PF!

Isn't R just the distance from P to each wire (so you'll need two equations, one for the field from each wire, and with different R's)?

3. Jul 27, 2009

### cate25

Re: Welcome to PF!

Thanks, tiny tim!