“STATIC ELECTRICITY” (CONTACT ELECTRIFICATION) IS CAUSED BY FRICTION?
November 15, 2010 Leave a comment
WRONG “Static” electricity appears whenever two dissimilar insulating materials are placed into intimate contact and then separated again. All that’s required is the touching. Chemical bonds are formed when the surfaces touch, and if the atoms in one surface tend to hold electrons more tightly, that surface will tend to steal charged particles from the other surface immediately as they touch. This causes the surfaces to become oppositely “charged”; they acquire imbalances of opposite polarity. One surface now has more electrons than protons, while the other has more protons than electrons. When the surfaces are later separated, the regions of opposite charge-imbalance also get separated.
For example, when adhesive tape is placed on an insulating surface and then peeled off, both the tape and the surface will become electrified. No friction was required.
Another example: when a thin material passes between rollers, sometimes the material becomes electrified. The rollers become oppositely electrified. For example, when newspaper passes between rubber rollers in a printing press, the paper becomes electrified and later on this can cause problems with cling and sparking. This situation in a large newspaper press inspired Robert VandeGraaff to design his famous generator.
Friction is not required. However, if one of the materials is rough or fiberous and does not give a very large footprint of contact area, then the process of rubbing one material upon another can greatly increase the total contact area. Friction may also remove thin layers of oil or oxide, exposing a more pure surface beneath. The peeling tape does not have to be rubbed in order to generate charge-imbalance, but the hair does need to be rubbed by the balloon. But the rubbing is not the cause of electrification, electrification can come about purely from contact. The term “Frictional electricity” is misleading. I try to instead use the terms “Contact Electricity” or “Electrification by Contact,” or “separation of charge,” or “creating charge imbalance.”