Have you ever wondered why batteries sometimes need to be inserted in alternating directions?

A typical electronic circuit has lots of components connected together with wires. How these connections are made is important and can lead to very different results depending on what’s being connected.

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.

Electronic components don’t care about how they’re arranged in a circuit or which direction they’re facing. The only thing that matters is how they’re connected. If current has to pass through multiple resistors, then they’re in series with each other and the total resistance will be the sum of all of the resistors. In effect, they all act like a single resistor.

If current can pass through any of multiple resistors, then they’re in parallel to each other and the total resistance will be lower than the smallest resistor. How much lower depends on how many resistors and their values. What you do is add the reciprocals of each resistance and then take the reciprocal of that sum to get the total resistance. A reciprocal of a number is just 1 divided by the number. So the reciprocal of 5 is 1 divided by 5. The reciprocal of 10 is 1 divided by 10. A good calculator will even have a button just for this purpose. It’ll be labelled as 1 over X.

The important thing to remember is that placing resistors in series increase the total resistance and placing them in parallel lowers the total resistance.

What about capacitors? They can also be placed in series or in parallel. Do they behave the same way? They actually are just the opposite. If you put multiple capacitors in series, then the end result is as if you replaced them all with another capacitor where the plates are spaced further apart. This lowers the total capacitance. And putting multiple capacitors in parallel is like increasing the size of the plates. That will increase the capacitance.

So when you have capacitors in series, you calculate the total capacitance just like resistors in parallel by adding the reciprocals and then taking the reciprocal of that. And capacitors in parallel add their capacitance just like resistors in series.

Listen to the full episode to understand how batteries behave in series and parallel.