7.1 Static Charge

 Electric charges that can be collected and held in place  If you recall from the chemistry unit, an atom has protons (positive) and neutrons (neutral) in the nucleus and electrons (negative) around the outside  If protons equal electrons then the atom is neutral  All solid materials are charged by the transfer of electrons  If electrons are lost then the atom or object is positive  If electrons are gained then the atom or object is negative

 Friction between two objects can result in one object losing electrons and the other object gaining electrons  Acetate (transparency plastic) rubbed with paper towel gained electrons from the paper towel to become negative (and conversely, the paper towel is positive)  Materials that do not allow charges to move easily are called electrical insulators  Glass, plastics, ceramics and dry wood  Materials that allow electrons to travel freely are called electrical conductors  Metals like copper or aluminum

 The unit of electrical charge is called a Coulomb (C)  1 C is the addition or removal of 6.25 x 1018 electrons  Charging an object through friction occurs naturally or artificially  In a cloud, the friction between rising hot air and the cloud produces lightning  Van de Graff generator using a moving belt to produce friction and a negative charge which is collected in the dome  Plastic sandwich wrap  Air ionizers take electrons out of the air  Paint can be given an electric charge to stick to vehicles better

 Sparks caused by a build up of static charge can blow up fuel trucks so a cables are attached to provide grounding (a way for extra electrons to get absorbed into the ground)  Lightning rods and ground wires are examples