Static electricity refers to the build up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Although charge exchange can happen whenever any two surfaces come into contact and separate, a static charge will only remain when at least one of the surfaces has a high resistance to electrical flow (an electrical insulator). The effects of static electricity are familiar to most people because we can see, feel and even hear the spark as the excess charge is neutralized when brought close to a large electrical conductor (for example a path to ground), or a region with an excess charge of the opposite polarity (positive or negative). The familiar phenomenon of a static â€˜shockâ€™ is caused by the neutralization of charge.
The materials we observe and interact with from day to day are formed from atoms and molecules that are electrically neutral, having an equal number of positive charges (protons, in the nucleus) and negative charges (electrons, in shells surrounding the nucleus). The phenomenon of static electricity requires a separation of positive and negative charges.
Removing or preventing a buildup of static charge can be as simple as opening a window or using a humidifier to increase the moisture content of the air, making the atmosphere more conductive. Air ionizers can perform the same task.
Items that are particularly sensitive to static discharge may be treated with the application of an antistatic agent, which adds a conducting surface layer that ensures any excess charge is evenly distributed. Fabric softeners and dryer sheets used in washing machines and clothes dryers are an example of an antistatic agent used to prevent and remove static cling.
Many semiconductor devices used in electronics are particularly sensitive to static discharge. Conductive antistatic bags are commonly used to protect such components, while people working on circuits containing them will often ground themselves using a conductive antistatic strap.
In the industrial settings such as paint or flour plants as well as in hospitals, antistatic safety boots are sometimes used to prevent a buildup of static charge due to contact with the floor. These shoes have soles with good conductivity. Anti-static shoes should not be confused with insulating shoes, which provide exactly the opposite benefit â€” some protection against serious electric shocks from the mains voltage.