Characteristics of resistor in series and parallel connection?

Resistors in series add resistance to an electrical circuit. For instance two 1 ohm resistors in series will have 2 ohms of resistance.

Resistors in parallel divide the resistance between them. Thus two 2 ohm resistors in parallel will have 1 ohms total resistance.

resistors of different sizes work the same way. a 4 ohm and 2 ohm resistor in series have 6 ohms resistance. While in parallel they will have .75 ohm resistance.

resistance formulas:

series: Req = r1+r2+r3....+rx

parallel: Req = 1/r1 + 1/r2 + 1/r3 ..... +1/rx