1. The problem statement, all variables and given/known data What is the (volume) charge density of a ring of radius [tex]r_0[/tex] and uniform charge density [tex]\lambda[/tex]? 2. Relevant equations The Dirac Delta Function 3. The attempt at a solution I've done a few line charge densities of straight wires along an axis (usually z, but on x as well), but I'm getting stuck at using the delta functions when wrapping the wire around in a circle. I am pretty sure I'll want the ring to be lying in the y-z plane, as the problem continues with an integral with [tex]\cos\theta[/tex] in the integrand and [tex]\theta[/tex], being measured from the z-axis, should give me a delta function there to make the integral easier. Any suggestions?