COMBINATIONS OF RESISTORS
As you remember from Chapter 10, two common ways of combining circuit
elements within a circuit is to place them either in series (one after the other)
or in parallel (that is, side-by-side)
To simplify the circuit, our goal is to find the equivalent resistance of the resistors.
Resistors are said to be in series if they all share the same current and if the total
voltage drop across them is equal to the sum of the individual voltage drops.