Electronics - Theory and Practice

Electric Current

What makes such a simple thing as an electric lamp glow? It is easy to pass the problem off with the statement, “The switch connects the light to the power lines and it glows” or something to that effect. But what does connecting the light to the power lines do? How does energy travel through solid copper wires? What makes a motor turn, a radio play? What is behind the dial that allows you to pick out one radio station from thousands of others operating at the same time? How fast is electricity really?

There are no simple single answers to any of these questions. Each question requires the understanding of many basic principles. By adding one basic idea to another, it is possible to answer, eventually, most of the questions that may be asked about the intriguing subjects of electricity, electronics, and radio. When the light switch is turned on at one point in a room and the light suddenly glows, energy has found a path through the switch to the light. The path used is usually along copper wires, and the tiny particles that do the moving and carry the energy are called electrons. These electrons are important to anyone studying electronics and radio, since they are usually the only particles that are considered to move in electric circuits. To explain what is meant by an electron, it will be necessary to investigate more closely the makeup of all matter.

The word “matter” means, in a general sense, anything that can be touched. It includes substances such as rubber, salt, wood, water, glass, copper, and air. The whole world is made of different kinds of matter.

The ancient Greek philosophers were always trying to find the ’stuff’ that the universe was made of. Even before Greeks, the Alchemists were trying to find the basic building blocks that all matter was made from, though most of the time their driving force was not so much science but the pursuit of wealth. They figured that if they could isolate the building blocks of matter then they would be able to ‘create’ matter themselves. One of their pursuits was the creation of the precious metal gold.

Water is one of the most common forms of ’stuff’ that we call matter. If a drop of water is divided in two and then divided again and again until it can be divided no longer and still be water, then we have arrived at the smallest possible piece of water. We have a water molecule. The ancient Greeks would have called the smallest droplet of water an atom (atomos). The word atom means indivisible. We know today that substances such as water can be divided into more fundamental bits.

The water molecule can be broken down into still smaller particles, but these new particles will not be water.
Physicists have found that there are three smaller particles making up a molecule of water: two atoms of hydrogen (H) and one atom of oxygen (0) as shown at right.

The symbols ‘H’ and ‘O’ are universal symbols used to represent Hydrogen and Oxygen. Oxygen, at normal temperatures, is one of several gases that constitute the air we breathe. Hydrogen is also a gas in its natural state; it is found in everyday use as part of the gas used for heating or cooking. If a gaseous mixture containing 2 parts of hydrogen and 1 part of oxygen is ignited, a chemical reaction in the form of an explosion takes place. The residue of the explosion will be water (H20) droplets.

As a child, (much to my mothers dismay) one of the experiments I enjoyed the most was mixing Hydrogen and Oxygen gases in a ratio of 2 to 1 in a jar and placing the jar in sunlight. A violent explosion would occur as the sunlight triggered a combining of the gases to produce water and release a significant amount of excess energy in the process. This is not an experiment that I would recommend. I still have all my fingers, however this is just the result of being lucky more than anything else.

So, water is made up from two atoms, hydrogen and oxygen. Water is a molecule. A molecule is a substance that is made up of groups of atoms. If you divided a droplet of water down to its smallest possible size you will have a single molecule of water. If you had the means to divide the water molecule further, you will no longer have water; you will have the atoms (hydrogen and oxygen) that make up water. The chemical name of water then is Di-Hydrogen Oxide.

It has been found that atoms are also divisible. An atom, being made up of at least two types of particles: protons and electrons, and a third particle called a neutron. Don’t let these names concern you too much. For our purposes the most important particle is the electron, at this time. Electrons and protons are called electrical particles, and neither one is divisible (in normal environments). All the molecules that make up all matter of the universe are composed of these electrical proton-electron pairs.

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