You can receive a mildly unpleasant shock and produce a little spark if you touch a metal doorknob after walking across a carpet. Vigorously brushing your freshly washed hair makes all the hairs fly apart. A plastic comb that you’ve run through your hair will pick up bits of paper and other small objects, but a metal comb won’t.
The common factor in these observations is that two objects are rubbed together. Why should rubbing an object cause forces and sparks? What kind of forces are these? Why do metallic objects behave differently from nonmetallic? These are the questions with which we begin our study of electricity.
Our first goal is to develop a model for understanding electric phenomena in terms of charges and forces. We will later use our contemporary knowledge of atoms to understand electricity on a microscopic level, but the basic concepts of electricity make no reference to atoms or electrons. The theory of electricity was well established long before the electron was discovered.