Two resistors are in series if and only if current that enters one resistor must enter the other resistor. That is, they are connected end to end in a row (but not both ends). In each of the following diagrams, R1 and R2 are in series (with respect to the terminals). Even in the last case, because no current can flow through R3.
Contrast this with the following diagrams where R1 and R2 are NOT in series:
Two resistors are in parallel if and only if the voltage is the same on both. That is, both ends are connected together. In each of the following diagrams, R1 and R2 are connected in parallel.
On the otherhand, in each of the diagrams below, R1 and R2 are NOT in parallel:
© Calvin College, 2000
This page was written and is maintained by Steve VanderLeest.
It was last modified on 1 Mar 2000.