Object charged by friction method process called triboelectrification (or after the friction between the two different types of objects, an object of positively and negatively charged another object).
Cause triboelectrification, because friction makes things get extra electrons, or lose electrons. Get the extra electron negatively charged objects, objects lose electrons positively.
Triboelectrification definition: when two objects are rubbed, some bound tightly in electronics are often transferred from one object to another object, so negatively due to electron neutral objects, objects lose electrons is positively charged.
Friction there are two objects with charge: silk by rubbing glass rods with the charge is a (positive), the fur rubbing hard rubber rods with the charge is another (negative).