A photo shows a child sliding down a spiral-shaped slide, with his straight hair standing on end.
Figure 18.1 This child’s hair contains an imbalance of electrical charge (commonly called static electricity), which causes it to stand on end. The sliding motion stripped electrons away from the child’s body, leaving him with an excess of positive charges, which repel each other along each strand of hair. (credit: Ken Bosma, Wikimedia Commons)

Electrostatic Forces

You may have been introduced to static electricity like the child sliding down the slide in the opening photograph (Figure 18.1). The zap that he is likely to receive if he touches a playmate or parent tends to bring home the lesson. But static electricity is more than just fun and games—it is put to use in many industries. The forces between electrically charged particles are used in technologies such as printers, pollution filters, and spray guns used for painting cars and trucks. Static electricity is the study of phenomena that involve an imbalance of electrical charge. Although creating this imbalance typically requires moving charge around, once the imbalance is created, it often remains static for a long time. The study of charge in motion is called electromagnetism and will be covered in a later chapter. What is electrical charge, how is it associated with objects, and what forces does it create? These are just some of the questions that this chapter addresses.