Series Resistors

Resistors in series have an equivalent (replacement) resistance, Req , given by

             Req = R1 + R2 + R3 + ….

 See Figure 1.  Note that the current through all series circuit elements is the same and that the change in potential across the complete series leg is the sum of the potential changes across each of the series circuit elements.

             Vb - Va = + V1 + V2 + V3 = - I*R1 - I*R2 - I*R3

 for the current direction shown.