Homework Statement The linear charge density for a ring of radius R which lies in the xy-plane (center at the origin) is given by:
\eta(\phi) = \left\{
\begin{array}{c l}
+\lambda & \mbox{if } 0<\phi<\frac{\pi}{2} \\
- \lambda & \mbox{if } \frac{\pi}{2}<\phi<\pi \\
+\lambda &...