Our approach will be to begin with a simple circuit and then generalize the analysis to more
complicated ones. The circuit shown in Fig. 2.15 will serve as a basis for discussion. This circuit
consists of an independent voltage source that is in series with two resistors. We have
assumed that the current flows in a clockwise direction. If this assumption is correct, the
solution of the equations that yields the current will produce a positive value. If the current is
actually flowing in the opposite direction, the value of the current variable will simply be
negative, indicating that the current is flowing in a direction opposite to that assumed. We have
also made voltage polarity assignments for and These assignments have been made
using the convention employed in our discussion of Ohm’s law and our choice for the direction
of i(t)—that is, the convention shown in Fig. 2.14a.