How does a styrofoam ball work?
Initially the Styrofoam ball or the acetate plastic strip carried an electric charge. When a charged object is placed close to an uncharged object an induced charge can develop on the uncharged object. This means that there can be some displacement of charge in the uncharged object and electrons can be be either pushed to or pushed away from the surface (depending on the charge on the second object). This results in the two surfaces having opposite charges and attracting each other. Once the two surfaces touch one of two things can happen. In the case of the acetate strip and the Styrofoam ball some charge can move from one surface to the other. These two objects then carry the same polarity of charge and start to repel each other. There are cases when charge does not transfer when the objects come into contact and they will continue to attract each other. This is the case with a charged rubber balloon and a painted wall. A charged rubber balloon can be made to stick to a wall.
