Electrical Circuit

An electrical circuit is includes of individual electrical components, like transistors, resistors, capacitors, diodes and inductors, which are connected by the conductive traces or wires via which electricity could flow. In a field as diverse as electrical engineering, you might well ask whether all of its branches have anything in common. The answer is yes—electric-circuits. An electrical circuit is a mathematical model that approximates the behavior of an actual electrical system. As such, it provides an impor­tant foundation for learning—in your later courses and as a practicing engineer—the details of how to design and operate systems such as those just described. The models, the mathematical techniques, and the language of circuit theory will form the intellectual framework for your future engi­neering endeavors.

Note that the term electric circuit is commonly used to refer to an actual electrical system as well as to the model that represents it. In this text, when we talk about an electric circuit, we always mean a model, unless otherwise stated. It is the modeling aspect of circuit theory that has broad applications across engineering disciplines-Circuit theory is a special case of electromagnetic field theory: the study of static and moving electric charges. Although generalized field theory might seem to be an appropriate starting point for investigating electric sig­nals, its application is not only cumbersome but also requires the use of advanced mathematics.

The basic assumptions which allows use to use the electrical circuit theory instead of the electromagnetic field theory, is in order to understand the physical system represented by the electronic circuit. These assumptions are as follows:

Electrical effects occur instantly all over the system. We could make this assumption since we know that the electrical signals travel near or at the speed of light. Therefore, if the system is physically small, electric signals move through it so quickly that we can con­sider them to affect every point in the system simultaneously. A sys­tem that is small enough so that we can make this assumption is called a lumped-parameter system.

The net charge on each element in the electric system is all the time zero. Therefore no component could collect a net excess of charge, although some components, as you will learn later, can hold equal hut oppo­site separated charges.

There is no magnetic coupling between the components tit a system. As we demonstrate later, magnetic coupling can occur within a component.

Questionnaire:

• What is electrical circuit? Explain.