Magnetic Field Direction in a Square Arrangement of Electric Currents

[singh390]

This problem doens't seem hard, but I am rusty on the right hand rule...
Four electric currents, equal in magnitude are arranged at the corners of a square as shown in the figure.
http://img368.imageshack.us/img368/2654/fourcurrents7jc.jpg
Two currents go into the page (marked by x), and two are pointing out of the page (marked by a dot). Point a is at the center of the square, and points b and c are in the middle of two of the sides. What is the direction of the magnetic field at points a, b, and c?
I am guessing a and b are down and c is zero? Is this right? I am screwed if I get this problem wrong :(

 

[NateTG]

All three are down. Most likely you forgot that the currents that are flowing out of the page contribute to the magnetic field at C.

 

[Ouabache]

You proably want to calculate contribution of magnetic field from each current carrying line at the points of interest. the analytical solution will tell you how much magnetic field is there...

NageTG why are you sure that the direction of magnetic field is down at all three points?

 

[singh390]

yup, I got it. They're all down. Thanks!