Voltage and Current Division in Resistive Circuits:
The corresponding resistance of series combination of resistances is the addition of all resistances connected in series.
Req = R1 + R2 + R3
Figure: Resistances in Series
In series circuit, current remains similar through all of the resistances whereas the voltage is divided in all resistances.
V = V1 + V2 +V3
= IR1 + IR2 + IR3
= I (R1 + R2 + R3) = I Req