The potential divider is a device designed to limit the voltage across a pair of terminals for whatever reason. It does this by placing a resistorbetween the output terminals, in series with another resistoras shown in the diagram below.

The input voltageis split in the ratio of the two resistances, so that the output voltage is given by

Eitherorcan be replaced by a variable voltage so thatcan be varied with a dial. If is replaced with a variable resistor of maximum resistancethencan vary betweenandwhere for the latter, the variable resistance is set to zero.

If R_2 is replaced with a variable resistor of maximum resistancethencan vary between 0 andand

A potential divider can act as a safety device, because if there is a short circuit in the input circuit then thewill limit the current and if there is a short circuit in the output circuit thenwill limit the resistance.

A potential divider can be used to measure a resistanceConnect in in position ofand measurethenIfandare known thencan be calculated.