Circuit Diagram Symbols

4.4 Circuit Diagram Symbols

In a circuit diagram, the cells are represented by the symbols shown below. 

Electric cell symbol

Two cells in series symbol

Cells in series symbol

The long, thin stroke represents the positive electrode; while the short, thick stroke represents the negative electrode of the cell. These are conventional symbols and the polarity marks (+ or -) may be omitted.

Most electric cells source are 1.5 volts when new. This electric potential is too weak to deliver a large amount of electric energy. When this is needed, two or more cells are used. For example, a torch requires two size D cells to give enough light. But more powerful torches require three or four such units. Similarly, small radios require three size D cells, while the large ones require as many as twelve.

In principle, the term battery refers to more than one cell when used or connected together. Consequently, the two dry cells in a torch form a battery just as the six dry cells in the radio. The individual dry cell does not make a battery.

At times, manufacturers connect many cells and house them together to form powerful batteries. The 12-volt car battery consists of six lead-acid cells connected and housed in the same casing. In doing this the battery has enough power to start a car engine. Individual cells or batteries may be connected in various ways to achieve the required voltage and current supply.