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Tuesday, 02 April 2013 13:29

Basic Electricity, Part 1

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What Electricity is and Where it Comes From

Electricity is a fundamental force in nature. It is all around us. We are virtually bathing in it at all times in the form of radio and television signals, microwave energy, radar, etcetera. Furthermore, our bodies run on electrical impulses; messages sent from our brains, through the nerves to the muscles causing contractions, both voluntary and involuntary.
Electricity is an electron in motion, and electrons are the negatively charged particles, which orbit the nucleus of an atom. In order to understand electricity, it is best to visualize it in some way. Think of the moon orbiting around the earth. The earth is analogous to the nucleus of an atom, and the moon is analogous to the electron. The whole system of the earth and the moon is then analogous to the simplest atom in nature, the hydrogen atom.

What are electrical charges? Electrical charges suggest a state of attraction between two bodies. Using the analogy of the earth and the moon, the earth would have a positive charge and the moon a negative charge. Similarly, the hydrogen atom possess a single positively charged proton in its nucleus; and orbit in around that nucleus, in equilibrium, is a single negatively charged electron. As long as there are an equal number of positive and negative charges, there exists a state of equilibrium (or balance). In studying electricity, it is the negatively charged electrons with which we are primarily concerned. When we cause a movement, or flow, of these negatively charged electrons, we then have established an electrical current.

The Principle of Charges

The principal of charges states that like charges repel and unlike charges attract. Remember when you were a child and you played with magnets? The two north poles (ends) of the magnets would not come together. Similarly, the two south poles would also repel each other. So it is with two positive or two negative charges; they will repel each other. On the other hand, the north and south poles of the magnets will attract, or come together; and so too will a positive and negative electrical charge.
In electricity, electrons are negatively charged particles, then an abundance of electrons on a surface will give that surface a negative electrical charge, and conversely; a lack of electrons on a surface will give that surface a positive electrical charge.

Conductors and Insulators

By definition, a conductor is a material or element that easily passes an electrical current (flow of electrons). An insulator is a material or element that will not easily pass an electrical current. Although modern science is on the verge of discovering alleged perfect conductors, for our purposes and understanding there are neither perfect conductors, nor insulators. Hence, a good conductor is a material, which presents little resistance to a flow of electrons, and a good insulator is a material which presents much resistance to a flow of electrons.
Electrical circuits need both insulators and conductors in order to accomplish the tasks we desire. The determination of what makes a good conductor versus a good insulator goes back to the basic elements in nature from which all things are made. As we previously stated, hydrogen is the simplest atom in nature having but a single positively charged proton in its nucleus, and a single negatively charged electron orbiting around its nucleus. All of the rest of the basic elements in nature have different and more complex atomic structures with more positively charged protons in their nucleus and an equal number of negatively charged electrons orbiting at various distances from their nucleus in what are called valence bands. This is in much the same way as our solar system with the sun as the theoretical nucleus and the planets, Earth, Mars, Jupiter, etcetera orbiting at various distances as theoretical electrons. It is the atomic structure of an element which determines whether it is a good conductor or a good insulator. The more complex elements have several orbits, or valence bands, located at various distances from the nucleus. This is the same idea as the planets of our solar system circling our sun (nucleus) as various valence bands of an element which ultimately determines conductivity.
When the outer valence band of an element is less than half full of electrons, it is a good conductor. Conversely, when the outer valence band is more than half full the element is a good insulator. Think of it as if the element with few electrons in its outer orbit would rather give them up than go look for more. Similarly, the insulator wants to keep its electrons. Remember, when the electrons do not move, there cannot be a flow of electrical current.
It probably comes as no surprise that all of the metals such as copper, aluminum, iron, gold, silver, mercury, etcetera have loosely bound outer valence electrons and are good conductors. The practical insulators used in electrical circuits are molecular substances, which are made up of two or more of the basic elements, rather than the basic elements themselves. Examples of good insulators are ceramic, glass, dry wood, and mot plastics.

The Basic Forms of Electricity

Essentially, electricity exists in one of three somewhat broad forms. They are static, direct, and alternating.

Static Electricity

The first form, static (or at rest) is familiar to all of us. Remember combing your hair on a dry day or walking across a carpet in the wintertime, then touching a metal object? What happened was that the comb, or carpet, caused negatively charged electrons to be rubbed off from your body. You then acquired a static positive (lack of electrons) electrical charge, and when you touched some metal object which was connected to the Earth, and any resistance to a flow of electrons, and an abundant supply of electrons, your electrons were restored in a rather abrupt way, probably startling you in the process. Static electricity has little practical use because, in order to do a meaningful amount of electrical work, we need to have an abundant, continuous supply of electrons. Another example of static electricity is a battery. When you purchase a battery at the store, it possesses an electrical charge of static electricity. When you place the battery in a flashlight, or some other electrical device, only then can it do electrical work. When you turn on the switch you convert static electricity to the second form of electricity with which we are concerned: direct current.

Direct Current

Direct current plays a very important role in the practice of electrolysis; as a matter of fact, it is responsible for our being called electrologists.
Direct current is a flow of electrons from point "A" to point "B" – or more correctly stated, from the negative terminal (or pole) to the positive terminal. As we will see later, direct current can be produced by means other than batteries; however, it is important to note that all batteries produce direct current. All batteries have two terminals: one positive and one negative. When the battery possesses an electrical charge, and when we connect it in an electrical circuit of some sort, the negatively charged electrons leave the negative terminal, go through the circuit (doing electrical work), and return to the positive terminal. When all of the available electrons have made it to the positive terminal, then the battery has reached a state of equilibrium, or discharge, and no more electrical work can be done. In the case of a flashlight, the light goes out.
Another important point for us as electrologists is that all batteries contain chemicals, and as we already stated all batteries produce direct current. The important fact is that the converse is also true; direct current produces chemicals. This fact is the very foundation of our profession. The process of producing chemicals from direct current is called electrolysis.

Alternating Current

Alternating current is also a flow of electrons, but in a quite different way. Unlike direct current (which flows from point "A" to point "B"), alternating current flows from point "A" to point "B", then back again. In other words, alternating current flows alternately both ways in an electrical circuit; first one way, then the other. This is also sometimes called sinusoidal current.
Virtually all wall outlets are alternating current outlets with very few exceptions. Only in some very old commercial buildings are there any wall outlets with direct current. There are several important differences between direct current and alternating current, which we need to understand, because as electrologists we work with forms of both direct and alternating current.
The rate at which the reversal of direction takes place in alternating current is known as frequency. Since direct current is always going in the same direction, and does not reverse, there is no frequency associated with direct current. In the United States, the rate of reversal or frequency for standard electric power is standardized at 60 cycles per second, or Hertz. Cycles is a generic term indicating that there are 60 periods when the electrons go from zero to a maximum positive point, back through zero to a maximum negative point, and then back to zero again all in one second of time. The word Hertz is synonymous with cycle, and has been adopted widely in recent years in order to give credit to Henrich Hertz who, in the late 1800s, discovered alternating current. In much of the rest of the world, the standard power frequency for alternating current is fifty-Hertz. Note that the words "per second" are rarely stated when we speak of cycles, or Hertz; however, per second is implicit in the correct definition.
Because alternating current reverses direction so frequently, for all practical purposes it has no polarity. Did you have to think which way you plugged in your hair dryer this morning? Maybe you said, "Yes, it has three prongs," or "yes, it has a fat prong, and a skinny prong." Most hair dryers, and for that matter most handheld electrical appliances produced today, have only two prongs of the same size, and can be plugged in either way. The point here is that in spite of the fact that some electrical appliances have three prongs, or plugs with one wide and one narrow prong that can be plugged in one way, many electrical appliances can be plugged in either way. This is proof that alternating current has no polarity, because as we previously stated that at any moment in time the current is reversing itself and going the other way. The reason some appliances have three prongs – or wide and narrow prongs that can only be plugged in one way – is for purposes of safety from electrical shock hazards, not polarity, per se.
The next important difference between direct and alternating current has to do with chemical effects. We previously said that chemicals can produce direct current and that direct current can produce chemicals. Have you ever heard of alternating current battery? There is no such thing, and just as chemicals do not produce alternating current, alternating current does not produce chemicals. This is an important point to remember in electrolysis. Direct current produces chemical effects; alternating current does not. Another way to understand this phenomenon is to realize that whatever chemical effects which would be created with alternating current when the current is traveling in one direction, would be canceled out when the current is traveling in the other direction.
Now that we understand the basic forms of electricity, let us see how we can put them to work for us.

Part 2 of this article will be printed in t he next issue of DERMASCOPE Magazine.

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