So, I want to point out that this is the same formula that you saw for

parallel resistors, but here you're using it for series capacitors.

Here's an example.

Let's find the effective capacitance of the combination below.

All right,

we'll start by finding the effective capacitance of the series combination.

And we recall the formula for that is 1 over 1

over 2 microfarads + 1 over 8 microfarads.

But since this formula like the formula for

parallel resistors we know we can write it more

conveniently at least for me this way,

which is going to give us 1.6 microfarads.

So far then what we have is a 3 microfarad capacitor and

parallel with the effective 1.6 microfarads.

And we remember that when you have parallel capacitors,

you simply add their capacitances to get the effective,

and that means that our final result is 4.6 microfarads.

Summing up, the key concepts are the parallel formula which looks

like the series formula for resistors but this is for parallel capacitors.