The , sign convention of Figure 5–4(a) has a deeper meaning than so far
considered. Voltage exists between points, and when we place a at one
point and a at another point, we define this to mean that we are looking at
the voltage at the point marked with respect to the point marked . Thus,
in Figure 5–4(b), V 6 volts means that point a is 6 V positive with respect
to point b. Since the red lead of the meter is placed at point a and the black
at point b, the meter will indicate 6 V.