Suppose that a spherical shell $B$ has inner radius $a$ and outer radius $b$ with a spherically symmetric internal charge density $\rho(r)=10kr^2$. What is the total charge?

Suppose instead that the shell is cylindrical, with the same inner and outer radii, but with a cylindrically symmetric internal charge density $\rho(r)=10kr^2$. What is the total charge?

Do you see the difference?? The coordinates $r$ in these two examples are different, with the first being the spherical radius, and the second being the cylindrical radius!

: Add some questions about theta and delta functions and limits