A level revision

Potential dividers

Potential dividers, as the name suggests, divide potential. Electrical potential in fact using resistors like in the circuit below:

The two voltages across the two resistors are related by a simple relationship:

This is as a result of Ohm's law.

Alternatively a more useful and altogether powerful equation for calculating the output of the potential divider is:

Worked example

A potential divider made from two resistors of 100 Ohms and 200 Ohms is supplied with a voltage of 12V. What are the potential differences across the resistors?

This question involves using the relationship between the ratio of voltages and resistances. Since the resistances are twice as much as each other so are potential differences, hence the potential difference across the 200 Ohm resistor is 8V and the 100 Ohm resistor is 4V.

You could also use the full equation with R₁ as 100 and R₂ as 200: