Before we discuss the basics of electricity and electronics, we need to understand what matter is. Matter is anything that occuples space and has mass, or weight. Wire, rubber, and glass are examples of matter. Scientist study the properties of matter in order to know how it works. Energy has different forms, such as heat energy and electric energy. Electric energy result from the motion of tiny bits of matter called electrons. Energy can make changes in materials, such as putting them together, taking them appart, or simply moving them from one place to another.The basic unit of matter is the atom. In studying electricity and electronics, it is important for you to understand the atom, because the electron is one of its parts. In this unit, the structure of the atom and its electrical properties are discussed
Structure of the atom
An atom is made up of tiny particles. Two of these particles, the elctron and the proton, are important to our studies.
Electrons move around the center, or nucleus, of an atom in paths. These paths are usually called shells. An atom can have several shells around its nucleus. Each of these shells can have only up to a certain number of electrons. This number is called the quota of a shell. When every shell of the atom contains its quota of electrons, the atom is said to be in a stable condition. The nucleus of the atom is made up of particles called protons and neutrons. These are held together tighty by a binding energy.
All electrons are alike, and all protons are alike. Thus, atoms differ from one another only in the number of electrons and protons they contain. The number of protons in the nucleus is the atomic number of that atom. Neutrons weigh about the same as protons. The term atomic weight refers to the total number of particles (both protons and neutrons) in the nucleus of an atom.
Elements, compounds, and molecules
When all the atom is a substance is called an element, copper, iron, and carbon are among the more than 100 different elements known to exist. Different elements can combine to form a subtance called a compound. Water, sugar, and plastic materials are exemples of compounds.
The smallest particle of a compound that has all the properties of that compound is called a molecule. A molecule contains atom of each of the elements that form the compound.
Charges
Electrons and protons have tiny amounts of energy known as electric charges. Electrons have negative (-) charges. Protons have positive (+) charges. Neutrons have no electric charge. Thus, they are natural. The amount of the negative charge of each electron is equal to the amount of the positive charge of each proton. These opposite charges attract each other. This attraction helps hold the atom together.
Under normal conditions, these negative and the positive charges in a atom are equal in value. This is because the atom has an equal number of electrons and protons. An atom in this condition is said to be elctrically neutral.
Valance elctrons
Elctrons in the outermost shell of an atom are called valence electrons. In the study of elctricity and electronics, we are concerned mostly with the behavior of valence electrons. They can, under certain conditions, leave their “parent” atoms. The number of valence electrons in atoms also determines important electrical and chemical characteristics of the subtance.
Energy levels and free electrons
The electrons in any shell of an atom are said to be located at certain energy levels. These are related to the distance of the electrons from the nucleus of the atom. When outside energy such as heat, light, or elctricity is applied to certainmaterials, the electrons within the atoms of these materials gain energy. This may cause the electrons to move to a higher energy level. Thus, they move farther from the nuclei of their atoms.
When an electrons has moved to the highest possible energy level (or the outermost shell of its atom), it is least attracted by the positive charges of the protons within the nuclei of the atom. If enough energy is then applied to the atom, some of the outermost-shell, or valence, electrons will leave the atoms. Such electrons are called free electrons.
Ions
An ion is a charged atom. If a neutral atom gains electrons, there are then more electrons than protons in the atom. Thus, the atom becomes a negatively charged ion. If a neutral atom loses electrons, protons outnumber the remaining electrons. Thus, the atom becomes a positively charged ion. Ions with unlike charges attract one another. Ions with like charges repel one another. The process by which atoms either gain or lose electrons is called ionization.
Electric charges in actions
A simple way of generating an electric charges is by friction. For exemple, if you rub a rubber balloon briskly with a wool cloth, electrons will move from the cloth to the balloon, causing the balloon to become negatively charged. If you then put the balloon to become negatively charged. If you then put the balloon against a wall, the balloon’s negative charge will repel electrons from the surface of the wall.
This will, in turn, cause the surface of the wall to become positively charged. The attraction between the opposite charges of the balloon and a small surface area of the wall is strong enough to hold the balloon in place
