Static electricity is the electric charge that gathers on the surfaces of objects, including people, under certain conditions. Static electricity is a common, naturally occurring phenomenon and, in most cases, the charge is so small that it cannot harm humans or animals. It can be dangerous to sensitive electronic components and, in rare cases, even to people. Lightning is a form of static electricity discharge.
Electricity is the effect of electrons moving from one area or object to another on the sub-atomic level. Static electricity collects on a surface when it has an imbalance of electrons, creating a positive or negative electric charge. This is normally discharged when the object or person contacts the earth or a conductive substance such as metal, restoring the electron balance. The earth or a similar “ground” will drain the charge without noticeable effect, but the conductor will create an electric energy transfer called a spark.
This process is best illustrated by example: A person wearing shoes made of leather, a substance with a positive charge, walks along a carpet made of rayon, which has a negative charge. Opposite charges attract, so electrons will transfer to the shoes, giving them a static electric charge; this transfer is known as the triboelectric effect. The carpet, being grounded, is not affected, but if the person then touches a metal doorknob, the charge will immediately transfer to the metal. The result is generally harmless, causing no more than mild discomfort to the person and, possibly, a brief visible spark.
In some conditions, however, even a brief spark can cause a great deal of trouble. Computer components such as semiconductors can be damaged by static electricity. In the presence of volatile gases or other substances, static discharge can result in fires or explosions. Many gas stations advise against using a cell phone while refueling because of possible static discharge. This seems to be an urban legend, but static electricity can indeed ignite fuel vapors; drivers should touch the metal of their vehicle far from the gas cap to discharge any static electricity before refueling.
Lightning is a spectacular and potentially deadly form of static discharge. Conditions in a thunderstorm give a cloud a powerful negative charge. When the positive charge of the earth or nearby clouds is strong enough, the charges equalize in a flash. The resulting lightning is millions of times more powerful than a domestic spark and is accompanied by tremendous heat and sound. When lightning is drawn to the earth, any potential conductors on the surface, including buildings, trees and people, can suffer severe damage in the blink of an eye.