24. Electric Force & Field; Gauss' Law

A glass rod is rubbed with silk, and a plastic rod is rubbed with wool. Afterward, to which object or objects will the glass rod be attracted?

A ring of charge lies in the xy-plane with its center at the origin. The ring has a radius of 87 cm and a total charge of $130\mu \mathrm{C}$. What is the linear charge density on the ring?