Copyright © 2007 Dorling Kindersley
A lightning strike demonstrates the incredible energy of electricity. This intense flash of heat and light is created naturally by static electricity. We use this same electric force to provide a clean, controllable power supply to our homes, farms, factories, and cities.
The electrons and protons inside every atom carry a property called an electric charge. Electrons have a negative charge and protons a positive charge. These charges either attract or repel each other. Unlike (opposite) charges attract, and like (the same) charges repel. The force they do this with is called electricity.
Electricity comes in two forms—as electric current when electric charges flow along wires in a circuit, and as static electricity, when electric charges do not move. Normally, most materials are neutral (have no charge). But if a material gains or loses large numbers of electrons, it becomes charged with static electricity.
Materials can become charged with static electricity by INDUCTION or by friction. When two materials rub together, friction transfers electrons from one to the other. This gives one material a negative charge, and the other a positive charge. A nylon comb gains a negative charge when it is pulled through hair.
Electric induction is the process by which a charged object can charge another object without touching it. A charged nylon comb, for example, will attract scraps of paper, even though the scraps are not charged themselves.
When the comb is brought close to the paper, the negative charge on the comb repels electrons in the paper to the side farthest away from the comb. This creates a positive charge (fewer electrons) on the side of the paper facing the comb. Positive and negative attract, so the paper is pulled toward the comb.