# Identifying between series and parallel resistors.

#### Mayor Haggar

Joined Dec 13, 2017
2
I am new to circuit analysis, and I am having some trouble telling the difference between series and parallel resistors. Some are obvious to me while others are not. Does anyone know a surefire way to tell which resistors are which? My textbook amazingly has no advanced examples of those kinds of problems; it only has two very simple ones.

#### WBahn

Joined Mar 31, 2012
26,398
Two components are in series if and only if whatever current flows in one component MUST flow in the other.

Two components are in parallel if and only if whatever voltage appears across one component MUST appear across the other.

#### Mayor Haggar

Joined Dec 13, 2017
2
Many thanks to you. That does make it easier to understand, and I can see the circuits better now.

#### bertus

Joined Apr 5, 2008
21,330
Hello,

Take a look at this simple schematic:

R2 and R3 are in series.
The combination of R2 and R3 are parallel to R1.

Bertus

#### WBahn

Joined Mar 31, 2012
26,398
Many thanks to you. That does make it easier to understand, and I can see the circuits better now.
And, if it hasn't already been pointed out by your text, not every circuit can be reduced via series and parallel combinations. There are many topologies that simply are neither. In some cases, there are techniques, such as delta-wye transforms, that can be used to transform these circuits into equivalent circuits that are series-parallel combinations. You will probably run into these transforms pretty soon. There are also analysis techniques that don't require reducing circuits to a single equivalent resistance in order to analyze them. If you haven't gotten to them yet, you should very shortly.