Electricity is as old as the universe. But knowledge about it is relatively new. Early humans were aware of electricity in the form of lightning. They learned of its power when they saw it starts fires and kills people and animals. But it was only about 300 years ago that people began to learn the basic laws of electricity. And only about 120 years have passed since electricity was first put to work. It has been only 100 years since the first practical electric lamp was invented, only 80 years since the vacuum tube was invented, and less than 40 years since the transistor was invented. Despite this brief time, electricity has greatly changed people’s lives—our lives. The universe consists of atoms and every atom contains at least one electron. An electron is the smallest particle of an atom and has a negative electric charge. When the movement of electrons is controlled, they are capable of doing work.

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