Standard electrocardiography measures time-dependent potential differences between multiple points on the body, giving cardiologists multiple perspectives on the heart?s electrical activity. In contrast, Fig. 22.26 is a ?snapshot? showing a more detailed picture at an instant of time. The lines are equipotentials on the surface of a human torso, associated with the heart?s electrical activity. Relative to the line marked V = 0, the potential is negative to the upper left (black) and positive to the lower right (color).

The electric field in the vicinity of the heart points approximately

a. from upper left to lower right.b. from lower left to upper right.c. from upper right to lower left.d. from lower right to upper left.

V = 0 V = -0.5 mV V= 0 FIGURE 22.26 Equipotentials on a human toro (Passage Problems 82-85)