Electronics Handbook/Components/Resistors/Series Connection

Resistor in series
Two or more resistor can be connected in series to increase the total resistance. The Total Resistance is equal to the sum of all the resistor's resistance. The total resistance In Series connected circuit Current and voltage will be reduced
 * [[Image:Resistors_in_Series.svg|200px]]
 * $$R_{eq}=R_1+R_2+R_3+...+R_n \,$$

Two equal value Resistor in series
When connecting two resistors of the same resistance the total resistance is doubled
 * R + R = 2R