99 Electricity and Magnetism-High

Electricity and Magnetism Written by David Dreier

Introduction Have you ever looked out a window at night and watched flashes of lightning split the night sky during a raging thunderstorm? 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 produce and harness electricity. Whenever you flip a switch to turn on a light, you are using electricity. Computers and televisions can't work without electricity. Electricity has become such an important part of our everyday lives that it is difficult to imagine the world without it. Magnetism is also a familiar part of our world. Perhaps you have played with magnets or use magnets on your refrigerator door. Did you know that magnetism is closely related to electricity? This book will teach you about electricity and magnetism, as well as 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. Electrical energy comes from tiny, invisible particles called atoms. Atoms are the smallest bits of elements, the basic substances that make up all matter. Inside each atom are even smaller particles called protons, neutrons, and electrons. Protons and neutrons make up an atom's center, called the nucleus. Protons have a positive charge, while neutrons are neutral, meaning they have no charge. Electrons have a negative charge. Charges of the same kind— such as two positive charges— repel each other. Charges that are opposite— a positive and a negative charge— attract each other.

Because electrons and protons are drawn to one another, you might wonder why electrons don't get pulled into the nucleus of an atom. They don't because electrons whirl around the nucleus very quickly. Their high speed keeps them from crashing into it. Normally, the number of positive protons and negative electrons in an atom is equal. Because the number of positive charges is equal to the number of negative charges, 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 acquires a negative charge because the electrons outnumber the protons. If an atom loses electrons, the protons outnumber the electrons, so the atom 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 with more protons than electrons is a positive ion. It is important to remember that charges do not exist by themselves. A charge is always connected to a particle. Negative charges are carried by either electrons or negatively charged ions. Positive charges are carried by protons or positively charged ions.

The Two Kinds of Electricity There are two kinds of electricity: static electricity and electric currents. They both involve the production and movement of charges. But they behave 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 positive and negative charges becomes strong enough, the particles quickly stream back together. Lightning is the most dramatic example of static electricity. In storm clouds, strong winds cause icy particles to collide violently. These collisions strip away many of the particles' outer electrons, leaving the cloud full of positive ions and free electrons. The positive ions move to the top of the cloud. The electrons, which have a negative charge, collect at the base of the cloud. When the collections of positive and negative charges get large enough, they rapidly flow back together. As they do, the energy of their motion heats the surrounding air and creates a lightning flash. 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!