Ohm’s Law in Graphical Form

A very valuable way of analyzing an electric circuit is by drawing a graph. No other method provides a more convenient or more rapid way to observe the characteristics of an electrical device.

The first step in drawing a graph is to obtain a table of data. The information in the table may be obtained by taking measurements on the circuit under test, or may be obtained theoretically through a series of Ohm’s law computations.

Since there are three variables (v, i, and R) to be analyzed, there are three distinct graphs that may be drawn. To construct any graph of electrical quantities, it is standard practice to vary one quantity in a specified way and note the changes, which occur in a second quantity.

The quantity, which is intentionally varied is called the independent variable and is plotted on the horizontal axis. The horizontal axis is known as the x-axis.

The second quantity, which varies as a result of changes in the first quantity, is called the dependent variable and is plotted on the vertical, or y-axis.

Any other quantities involved are held constant. When the equation of Ohm’s law is plotted, the graph is a straight line passing through the origin as shown in Figure 5.2.

Figure 5.2 Ohm’s Law in Graphical Form