Basics of Electronics (1) (E1)

The field of electronics comprises the study and use of systems that operate by Controlling the flow of electrons (or other charge carriers) in devices such as thermionic Valves and semiconductors. The design and construction of electronic circuits to solve Practical problems is an integral technique in the field of electronics engineering and is equally important in hardware design for computer engineering. All applications of Electronics involve the transmission of either information or power. Most deal only with Information.

Introduction:

Electricity and electronics are a part of our everyday lives. When we get up in the morning the first thing we do is turn on the light; we have just used electricity. The television that we watch, the stereos and radios that we listen to, our heat, our air conditioning, frequently even our cooking all use electricity in one form or another.

These devices work on electrical principles; you should possess a thorough knowledge of the principles of electricity and electronics. The purpose of this article is to introduce the readers to the principles of basic electronics. This task will discuss what electricity is, voltage, current, resistance, Ohm's law, and the color codes for resistors. In the succeeding task, we will cover the different types of circuits, the means of measuring and computing voltage, and current of batteries, especially those in a series-parallel circuit etc.

Electricity:

Composition of Matter:

 Matter is defined as anything that occupies space and has weight; that is, the weight and dimensions of all matter can be measured. Examples of matter include air, water, automobiles, clothing, and even our own bodies. Therefore, we can say that matter may be found in any one of three states: solid, liquid, and gaseous.

All material substances, solids, liquids, and gases, are made up of tiny Particles known as atoms. Atoms combine in small groups of two or more to form molecules. Atoms can be further subdivided into smaller particles, some of which have positive electrical charges and others which have negative electrical charges. The atoms of different material substances are discussed in the following paragraphs.

(1) There are over 100 different basic materials in the universe. These basic materials are called elements. Iron is one element, copper; aluminum, oxygen, hydrogen, and mercury are other elements. An element gets its name from the fact that it cannot be broken down easily into simpler (or more elemental) substances. In other words, these 100 basic elements are the building materials from which the universe is made. Close study of any one of these elements reveals that it is made up of those same basic particles, having a positive or a negative electrical charge.

(2) The basic particles that make up all the elements, and thus the universe, are called protons, electrons, and neutrons. A proton is a basic particle having a single positive charge; a group of protons produce a positive electrical charge. An electron is a basic particle having a single negative charge; therefore, a group of electrons produce a negative electrical charge. A neutron is a basic particle having no charge; a group of neutrons, therefore, would have no charge.

First, let us examine the arrangement of atoms in some elements, starting with the simplest of all, and hydrogen. The atom of hydrogen consists of one proton, around which is circling one electron (figure 1 on the following page). There is an attraction between the two particles, because negative and positive electrical charges always attract each other. Opposing the attraction between the two particles, and thus preventing the electron from moving into the proton, is the centrifugal force on the electron, caused by its circular path around the proton. This is the same sort of balance achieved when a ball tied to a string is whirled in a circle in the air.

The centrifugal force exerted tries to move the ball out of its circular path, and is balanced by the string (which can be defined as the attractive force). If the string should break, the centrifugal force would cause the ball to fly away. This is what happens at times with atoms. The attractive force between the electron and proton is sometimes not great enough to hold the electron in its circular path, and the electron gets away.

A slightly more complex atom is the atom of helium. Notice that there are two protons in the center. Because there is an additional proton in the center, or nucleus, of the atom, an electron must be added so as to keep the atom in electrical balance. Notice also that there are additional particles in the nucleus; these are called neutrons. Neutrons overcome the tendency of the two protons to move apart from each other. Just as unlike electrical charges attract, so do like electrical charges repel. Electrons repel electrons. Protons repel protons, except when neutrons are present. Though neutrons have no electrical charge, they cancel out repelling forces between protons in an atomic nucleus and thus hold the nucleus together.

A still more complex atom is the atom of lithium, a light, soft metal. Note that a third proton has been added to the nucleus and that a third electron is now circling around the nucleus. There are also two additional neutrons in the nucleus; these are needed to hold the three protons together. The atoms of other elements can be analyzed in a similar manner. As the atomic scale increases in complexity, protons and neutrons are added one by one to the nucleus and electrons to the outer circles or shells, as they are termed by scientists. After lithium comes beryllium with four protons and five neutrons, boron with five protons and five neutrons, carbon with six and six, nitrogen with seven and seven, oxygen with eight and eight, and so on. In each of these, there are normally the same numbers of electrons circling the nucleus as there are protons in the nucleus.

Composition of Electricity:

 When there are more than two electrons in an atom, they will move about the nucleus in different size shells. The innermost shells of the atom contain electrons that are not easily freed and are referred to as bound electrons. The outermost shell will contain what are referred to as free electrons. These free electrons differ from bound electrons in that they can be moved readily from their orbit.

If a point that has an excess of electrons (negative) is connected to a point that has a shortage of electrons (positive), a flow of electrons (electrical current) will flow through the connector (conductor) until an equal electric charge exists between the two points.

Electron Theory of Electricity:

A charge of electricity is formed when numerous electrons break free of their atoms and gather in one area. When the electrons begin to move in one direction (as along a wire, for example), the effect is a flow of electricity, an electric current. Actually, electric generators and batteries could be called electron pumps, because they remove electrons from one part of an electric circuit. For example, a generator takes electrons away from the positive terminal and concentrates them at the negative terminal. Because the electrons repel each other (like electrical chares repel), the electrons push out through the circuit and flow to the positive terminal (unlike electrical charges attract). Thus, we can see that an electric current is, in fact, a flow of electrons from negative to positive.

This is the reverse of the original idea of current flow. Before scientists understood what electric current was, they assumed that the current flowed from positive to negative. Their studies showed that this was wrong; they learned that current are the electron movement from negative (concentration of electrons) to positive (lack of electrons).

-to be continued…