Electrical Circuit.

The electrical circuit is the path in which the electricity moves. The properties of electrical circuits and the electrical quantities associated with them make an appropriate beginning for the study of the subject of electrical engineering, for electrical energy is in almost all practical applications utilized in circuits. These circuits are 

of various forms and extent, and are made for many different purposes, but all possess to a greater or less extent the same properties and involve the same electrical quantities. Suppose, for example, a door bell that is operated from two or three dry cells, as shown in Fig. 1. This combination forms an electrical circuit, typical of all electrical circuits. It contains a source of electrical energy (the battery), an energy transforming device (the bell), and the necessary connecting materials (wire and push button). It is closed upon itself and like the circumference of a circle has neither beginning nor end. (A table of symbols commonly used in representing the different pieces of electrical apparatus is given in Chapter 20.)