98 Electricity and Magnetism-Mid

Electricity and Magnetism Written by David Dreier

Introduction Have you ever watched flashes of lightning during a big storm at night? You might be surprised to know that lightning is a natural form of electricity. In the last two hundred years, people have learned how to make and use their own electricity. Whenever you turn on a light you are using electricity, Computers and televisions can't work without electricity, either. Electricity has become such an important part of our lives that it is hard to imagine the world without it. Magnetism is also a familiar part of our world. Perhaps you have played with magnets or have magnets on your refrigerator door. Did you know that magnetism is closely related to electricity? This book will teach you about electricity and magnetism, and how they are related.

What Is Electricity? You just learned that electricity? can be produced naturally or by people. But what is electricity? It is a form of energy. It comes from very tiny particles called atoms. Atoms are the smallest bits of elements, the basic substances that everything is made of. Inside each atom are even smaller particles called protons, neutrons, and electrons. Protons and neutrons make up an atom's center, called the nucleus. Electrons whirl around the nucleus. Protons and electrons have a feature called electrical charge. This feature is the source of electricity. Protons have a charge that scientists call positive. Electrons have an opposite charge called negative. Neutrons are neutral, meaning they have no charge.

Charges of the same kind repel each other. So two protons repel each other, and so do two electrons. Charges that are opposite attract each other. So a proton and an electron are attracted to each other. However, electrons do not get pulled into the nucleus, even though they are attracted by the protons. That is because they are moving so fast. The number of positive protons and negative electrons in an atom is usually equal. Because the charges are equal in number, they cancel each other out. The atom is neutral, meaning it has no charge.

Atoms can gain or lose electrons by contacting other atoms. If an atom gains electrons, it is no longer neutral. It now has a negative charge. If an atom loses electrons, the protons outnumber the electrons. The atom now has a positive charge. An atom that has a charge is called an ion. An atom that has more electrons than protons is a negative ion. An atom that has more protons than electrons is a positive ion.

The Two Kinds of Electricity There are two kinds of electricity. They are static electricity and electric currents. Both kinds of electricity involve the production and movement of charges. But they act in very different ways. Static Electricity Static electricity is caused by a buildup of negative charges in one place and positive charges in another. When the attraction between the separated charges becomes strong enough, the particles quickly stream back together. Lightning is caused by static electricity. In storm clouds, strong winds cause a buildup of electrons and positive ions. The charges collect in different parts of the cloud. When the collections of charges get big enough, they rapidly flow back together. This heats the surrounding air and causes a lightning flash. Most lightning occurs inside clouds or between clouds. WOWSER! A lightning bolt heats the air around it to about 30,000° C (54,000° F). That's five times as hot as the surface of the Sun! The burst of energy creates a bright flash of light. At the same time, the lightning bolt causes the air to expand violently. That is what produces thunder.