You can use resistors to divide voltage.

A circuit with just some resistors may not seem very interesting but you can learn something. If you put two resistors in-line with each other, then the total resistance will be the sum of each resistor. This type of arrangement is called in series. You can learn more by listening to the previous episode about series vs. parallel.

While you can think of multiple resistors in series as being equivalent to a single larger resistor they have an interesting property that will divide the voltage. Since they’re in series, there’s only one path for current to flow so that means that the current will be the same through each resistor. The total resistance will determine this current. And each resistor will share a portion of the voltage. If you have two resistors and they’re both the same value, then each will share half the voltage. But if one resistor is larger, then it will carry more of the voltage.

You can use this in designs where you want to adjust maybe the volume or brightness or speed of something. You can use a variable resistor called a potentiometer or pot for short. Most knobs that have a minimum and maximum amount they can be turned are actually variable resistors. Now if you have a newer device that has knobs that can turn as much as you want, then these are not potentiometers.