Figure 1
Resistors can be connected in series; that is, the current flows through them one after another. The circuits in Figure 1 and Figure 2 show two resistors connected in series. The arrow indicates the positive direction of the current. Since there is only one path for the current to travel, the current passing through each of the resistors is the same.
Figure 2 The voltage drop across the resistors must add up to the total voltage supplied by the battery. Resistors connected in series can be replaced with a single resistor, called an equivalent resistor, whose resistance equals the sum of the individual resistors: