Electricity is the flow of electrons within a conductor. You can get these moving electrons to do things for you in automotive systems, such as starting your engine, charging your phone, controlling vehicle emissions, and opening your windows. Electrical systems are everywhere in modern automobiles. Having a basic understanding of how electricity works can go a long way toward helping you repair automotive electrical systems.
The first thing to talk about is the flow of electricity. For the purposes of this article, we're going to say that electricity flows from positive to negative. Yes, there are other theories on electron flow, but to keep things simple we're going to stick with electrons flowing from positive to negative in this article.
To get this electricity to flow and go were we want it to, we use conductors. Conductors are materials that allow electrons to flow freely. Resistors are materials that inhibit electron flow. We use resistors to insulate our conductors so we keep the electricity flowing where we want it to go. Electricity is funny like that; if you let it, it will find the shortest route to ground, which might happen before you want it to. Insulators help keep this from happening.
Then there are semiconductors: transistors, resistors, and diodes, just to name a few. We use these to help control things in automotive electrical systems. Semiconductors can allow electron flow sometimes but not others. They can block electron flow in one direction, but allow it to flow in the other direction. They can also be used to change the resistance of a circuit based on temperature. Semiconductors are used extensively in computers and control systems. As a result, you run into a lot of semiconductors in automotive applications.
Another big component of an electrical circuit is the load. The load is what does the work in an electrical circuit. The load can be a lot of things. It can be a motor, a heating element, a bulb, or any number of other electrical components that do work. The load and the resistance in the circuit dictates the amount of current flow in the circuit. We'll talk more about that in a minute.
Aside from the wires that carry electricity and the wiring insulation that keeps the electricity on the path we want it to take, we also need the ability to control a circuit. We often do this with switches. Switches come in all shapes and sizes. They can be switches that we activate, or they can be activated automatically when certain conditions are met; they can also turn things off at a given time.
This is a very basic overview of what you'll find in automotive electrical systems. Now let’s talk about how we label and measure electricity in order to diagnose electrical faults.