Static electricity is an electrical charge at rest. Static electricity is most commonly created by friction and separation. Friction causes heat which excites the molecular particles of the material. When two materials are then separated, a transfer of electrons from one material to the other may take place

As electrons transfer, the absence or surplus of electrons creates an electrical field known as static electricity. The simple separation of two materials, as when tape is pulled off a roll, can also create this same transfer of electrons between materials, generating static electrical fields.

The amount of static electricity generated depends upon the materials subjected to friction or separation, the amount of friction or separation and the relative humidity of the environment. Common plastic generally will create the greatest static charge. Low humidity conditions such as those created when air is heated during the winter will also promote the generation of significant static electrical charges.

Materials that easily transfer electrons (or charge) between atoms are called conductors and are said to have "free" electrons. Some examples of conductors are metals, carbon and the human body's sweat layer. Materials that do not easily transfer electrons are called insulators. Some well known insulators are common plastics, glass and air. Both conductors and insulators may become "charged" with static electricity. When a conductor is charged, the free electrons give it the ability to discharge rapidly when it comes close to another conductor with a different potential.