Electrical Terms

Understanding of electrical terms is compulsory for engineers. As you study electricity in your engineering program, and as you work with electricity in the power plants, industrial plants, you will hear, read, and use various electrical terms. These terms have very exact meanings. You must know what each one means if you are to understand other people and make them understand you. The following terms explain the meaning of the most basic electrical terms.

Electric current the electrical term

Electric current is one of the basic electrical terms described as when electrons flow from one place to another, they make a current. The electrons always flow from a negative point to a positive (or less negative) point, because electrons have a negative charge.

Unfortunately, the direction of the current flow can be confusing. Some people think of a positive current that is in the opposite direction from the electron flow- that is, from positive to negative instead of from negative to positive. You must be careful to distinguish between the two kinds of flow. Both kinds are commonly used in words and diagrams.

The so-called “positive current” is from positive to negative. The “electron flow” is from negative to positive. The word “current” to mean electron flow-from negative to positive. The figure below shows the difference between positive current and electron flow.

Circuit

Electrons flow along with some kind of path in going from one point to another. This path is called a circuit. If the path has no gaps to stop the flow of electrons, the circuit is said to be complete or closed.

In case the path has a gap that the electrons cannot cross- for example, a break in a wire where the ends are separated by air- the circuit is said to be open. If another pathway provides an easier way a short circuit for the electrons to go from one point another, that part of the circuit is said to be shorted. The figure below shows the circuit that is complete, open, and shorted.

Potential difference

This term is the correct name for what is often called “voltage” or “electromotive force.” Potential difference is a measure of how much potential energy an electron has in one place compared to another place.

The greater the potential energy, the more work an electron can do in going from one place to the other. The potential energy of each electron also determines how much current will flow from one point to another in a given circuit.

Resistance

Every electrical pathway from one place to another has the property of resisting the flow of electrons. Some pathways resist the flow only slightly. For example, a thick copper wire offers very little resistance. Other pathways-for examples, an air gap-offer great resistance. The greater the resistance, the less the current for a given potential difference.

Cell

Electricity can be produced by chemical means. The arrangement of materials that produces a potential difference between two points by chemical resources is called a cell. Familiar cells include the dry cells used in flashlights, calculators, and radios.

Battery

When you connect two or more cells together, the combination is called a battery. If your calculator takes two dry cells, the grouping is called a two-cell battery.

The storage battery in a car or truck is usually a six-cell battery that produces a potential difference of 12V between the terminals. Each cell in such a battery produces a potential difference of 2 V between its internal terminals. The terminals of the cells are connected in such a way that their potential differences add together between the external terminals

As you study the remaining lessons in this course and the other courses in your series, make sure you learn the proper terms to use in discussing electricity, and the exact meaning of each term. Always use the correct terms, even if other people do not. If you use the wrong terms, you are likely to be misunderstood. In addition, other people will think you know less about electricity than you actually do.