Hi, I'm having trouble doing this problem: A truncated conical cylinder of graphite (bulk resistivity [tex] \rho = 1/\sigma [/tex]). The top of the cylinder has radius r = a, the bottom has r = b (b>a). Find the effective resistance between top and bottom of the cylinder. Show that the expression reduces to the usual one ([tex] R = \rho L / A [/tex]) when a = b. I know I need to do some kind of integration from a to b, but I really don't know how to set this up. Thanks.