Editing Electric charge (section)

== Role of charge in static electricity ==
[[Static electricity]] refers to the electric charge of an object and the related [[electrostatic discharge]] when two objects are brought together that are not at equilibrium. An electrostatic discharge creates a change in the charge of each of the two objects.

=== Electrification by sliding ===
{{Further|Triboelectric effect}}

When a piece of glass and a piece of resin—neither of which exhibit any electrical properties—are rubbed together and left with the rubbed surfaces in contact, they still exhibit no electrical properties. When separated, they attract each other.

A second piece of glass rubbed with a second piece of resin, then separated and suspended near the former pieces of glass and resin causes these phenomena:
* The two pieces of glass repel each other.
* Each piece of glass attracts each piece of resin.
* The two pieces of resin repel each other.

This attraction and repulsion is an ''electrical phenomenon'', and the bodies that exhibit them are said to be ''electrified'', or ''electrically charged''. Bodies may be electrified in many other ways, as well as by sliding. The electrical properties of the two pieces of glass are similar to each other but opposite to those of the two pieces of resin: The glass attracts what the resin repels and repels what the resin attracts.

If a body electrified in any manner whatsoever behaves as the glass does, that is, if it repels the glass and attracts the resin, the body is said to be ''vitreously'' electrified, and if it attracts the glass and repels the resin it is said to be ''resinously'' electrified. All electrified bodies are either vitreously or resinously electrified.

An established convention in the scientific community defines vitreous electrification as positive, and resinous electrification as negative. The exactly opposite properties of the two kinds of electrification justify our indicating them by opposite signs, but the application of the positive sign to one rather than to the other kind must be considered as a matter of arbitrary convention—just as it is a matter of convention in [[mathematical diagram]] to reckon positive distances towards the right hand.<ref>[[James Clerk Maxwell]] (1891) ''[[A Treatise on Electricity and Magnetism]]'', pp. 32–33, Dover Publications</ref>