Static electricity is the accumulation of an electric charge in an insulating material. For example, a plastic ruler rubbed with a dry cloth or a comb run through hair acquires a negative charge by picking up electrons from the cloth or hair. It can then attract small bits of paper, by altering the distribution of their originally neutral electric charge. Electric charges can be released suddenly. Called electrostatic discharge, this is what happens, for example, when you walk on carpet and feel a slight electric shock on touching a metal object. Electrostatics, the branch of physics that studies these phenomena, is governed by Coulomb's law.