This charge may be transferred from the material, creating an electrostatic discharge, or ESD, event. An electrostatic charge also may be created on a material in other ways such as by induction, ion bombardment, or contact with another charged object. However, triboelectric charging is the most common. How much charge is generated, where that charge goes, and how quickly, are functions of the materials' electrical characteristics. A material that prevents or limits the flow of electrons across its surface or through its volume is called an insulator.
Insulators have an extremely high electrical resistance.
A considerable amount of charge can be generated on the surface of an insulator. Because an insulative material does not readily allow the flow of electrons, both positive and negative charges can reside on insulative surface at the same time, although at different locations. The excess electrons at the negatively charged spot might be sufficient to satisfy the absence of electrons at the positively charged spot. However, electrons cannot easily flow across the insulative material's surface, and both charges may remain in place for a very long time. A conductive material, because it has low electrical resistance, allows electrons to flow easily across its surface or through its volume.