Static electricity is generated when two materials are rubbed together, with one gaining electrons and becoming negatively charged and the other losing electrons and becoming positively charged, as determined by their ranking on the triboelectric series. The triboelectric series ranks materials based on their tendency to gain or lose electrons through friction, with materials higher on the list more likely to become positively charged when rubbed against those below. Car tires are made of conducting rubber to prevent a buildup of static electric charge while driving.