Series Resistors
Two or more components are in series if they are connected one after another in the same path of a circuit. The current is constant through any components in series because it has only one path to follow. Once the current has two or more paths to follow, the series chain is broken.
This concept is illustrated in Figures 4 and 5. Figure 4 shows that once current enters the first resistor, it must flow through the other two with equal magnitude. It has to – it has no where else to flow. This is not the case in Figure 5. Current traveling through the first resistor splits once it reaches the other two resistors with some of the current flowing through R2 and the rest through R3.
How to combine series resistors
Combine series resistors by adding them together according to the equation shown below (where N is the number of series resistors). Note that placing a resistor in series with another always increases the overall resistance of the circuit. This means that RT must be larger than the largest resistor in the series chain. If you combine series resistors and get a number smaller than the biggest resistor, you’ve miscalculated.
Series Resistance Formula
Written by Ryan Eatinger (reatinge@ksu.edu). Thank you!