# Homework Help: Hairy Electro-Magnetics problem.

1. Mar 15, 2004

### frankR

A surface current equal to Js is flowing on the surface of a perfect conductor in the x-z-plane traveling in the positive x direction. At a distance y = L along the y-axis lies the central axis of a cylindrical conductor with radius “a” and having a volumetric current distribution Jv= Jo*r*ex traveling in the positive x-direction, where L > a. Find the condition for Jo where the H field is equal to zero in the regions, r <= a and r > a.

What I know:

Without posting a ton of equations I’ll tell you where I’m stuck. I used Biot-Savart laws for a surface current and a volumetric current and combined them to find the condition where the H-fields cancel.

I’m not sure how to handle the integrals for the Biot-Savart laws. I get infinities in the limits and everything explodes.Do you have make a one axis simplification to find where the fields cancel? I’m thinking you do because the math gets hairy. Or am I going in the wrong direction, do you use something other than Biot-Savart’s law?

Thanks

Last edited: Mar 15, 2004