6.02 The potential divider rule.

The potential divider rule can be used as a quick way of calculating voltage drops, when two resistors in series are connected to an e.m.f.

potential divider

Proof of the potential divider rule.

Therefore to find the voltage across a resistor in a potential divider circuit, we simply multiply the supply voltage by its resistance divided by the total resistance.

V2 = VS x R2/(R1 + R2).

Note the potential divider rule can be used when an e.m.f. is applied to any number of resistors in series.
The voltage across resistor A is given by, VA = VS x RA/RT .