# Definition of Equivalent Resistance [duplicate]

Is the equivalent resistance of two parallel resistors the resistance of the individual resistors or the sum of their resistances?

Is the $R_e$ of two series resistors their sum?

## marked as duplicate by Olin Lathrop, ACuriousMind♦, Kyle Kanos, Brandon Enright, BMSOct 28 '14 at 5:50

The two simplest networks are two resistors in series (add their resistances to get the equivalent) or in parallel (then $R_e=\frac{R_1R_2}{R_1+R_2}$). But more complex combinations are possible - and while there may not be a "simple" formula to compute their equivalent resistance, a network with just two terminals always has an equivalent impedance.
$1/R_e = \sum1/R_i$