Based on many conversations I’ve had with people over the years, I’ve come to the conclusion that, of all the elements that go into a car, electricity is, by a wide margin, the most misunderstood. And not just by the layman, either. Electricity is a hang up for technicians and engineers, as well.
I’ve also concluded that a great deal of this misunderstanding stems from the fact that electricity is invisible and formless, so its nature can be perceived only indirectly. Another reason for the misunderstanding is that electricity is not often taught well in many schools, possibly because the instructors don’t fully understand it, either.
In the following section, I portray electricity as a phenomenon — which it certainly is — that can be reckoned with and worked with.
So, what is electricity? What is this force that sparks the sparkplugs and lights the lights? Is it some kind of magic that only an engineer or scientist can understand? No!
Webster’s New Collegiate Dictionary puts it like this:
“Electricity is a fundamental entity of nature consisting of positive and negative kinds… usually utilized in the form of electrical currents.”
Mysterious, maybe, but not magic.
Let’s try to improve on Webster:
- Electricity has positive and negative charges.
- It is an invisible force.
- It can be controlled.
- It can do work.
- It can flow in a current from place to place.
- It can flow only in a completed circuit.
- It can be “stored” in a battery.
Pic. When the like poles (+ + or – -) of two magnets are close to each other, they repel. The unlike poles (+ and -) attract each other. This phenomenon is the basic key to understanding how electricity works.
Positive & Negative — In grade-school science, you probably learned that magnets are electrical in nature, with a north pole and a south pole. On some magnets, north is marked + (positive) and south is marked – (negative). Put two magnets close to each other and you’ll see that like poles ( + + or – -) repel each other and unlike poles ( + — ) attract each other.
This separation into positives and negatives is called polarity. It is the first important point about electricity, which will become clearer later. For now, just remember positive, negative, and the attraction between them.
The Invisible Force — You can’t see electricity because it operates at an atomic level. All matter is composed of atoms. They’re so tiny it would take millions of them to equal the width of the period at the end of this sentence. Atoms are composed of even smaller particles — protons, neutrons and electrons among them. The particles we’re concerned with are the electrons.
Pic. Principle of electrical flow depends on fact that atoms of some materials have loosely held electrons in their outer orbits. When loosely held electron is forced from its outer orbit, it is free to “hop” to another atom.
Electrons travel in circular paths around their atom’s nucleus, like planets around the sun. In some materials — copper wire for instance — the outermost electrons aren’t held too strongly. They’re free to hop randomly from one atom to another. Each time an extra electron hops into an atom, it pops another one loose. Because the activity of these free electrons is random, there’s nothing directional about their movements.
There are two devices in a car’s electrical system that are sources of excess free electrons: battery and generator. At one terminal there’s an excess of free electrons, and at the other terminal there’s not enough.
If you attach a copper wire between the two terminals of a battery or generator, free electrons begin to push into the copper wire. The random movement of the copper’s free electrons begins to take on a pattern. With pressure (voltage) behind and a void ahead, the electrons move in a more-or-less orderly fashion in one direction. This directional flow of electrons in the wire is called electrical current. Voltage is discussed later.
Conductors, Resistors & Insulators – As mentioned earlier, the outermost electrons in copper atoms are held relatively loosely. Silver is another metal with loosely held electrons. Materials such as these are called conductors because they freely conduct or carry electron movement.
Other metals conduct electricity, but not as well. In these metals, when a free electron hits an atom, some of its energy gets absorbed. So when the next electron is freed, it doesn’t have as much energy as the first one did. This slowing of electron movement is called resistance, and materials in which it occurs are called resistors. They conduct electricity, but tend to resist its movement. Examples of resistance metals are nickel, iron and nichrome.
Materials whose outermost electrons are firmly held are called insulators. Because there aren’t any, or not many, free electrons available, insulators can’t conduct electron flow — note the difference between a resistor and an insulator. Insulators include air, rubber, glass, wood, bakelite, cotton, and of course, the plastic insulation on electrical wire.
So, metals are capable of conducting electricity, although some act as resistors. Non-metals generally act as insulators.