Question: Well one problem boiled down to the following RC ciruit-
[![enter image description here](https://i.stack.imgur.com/nrscq.png)](https://i.stack.imgur.com/nrscq.png)

$C\_1$ was initially charged with $q\_o$ and I thought after closing switch connecting $C\_1$ and $C\_2$ the maximum current discharging will be $\frac{q\_0}{RC\_1}$. I could write the whole current equation but I think the time constant should be $R(C\_1 + C\_2)$ but the time constant given in the book is $\frac{RC\_1C\_2}{C\_1 + C\_2}$. How come? Aren't the capacitors are in parallel?

Answer: 
No. The capacitors are in series. This is because one side is at the same potential. But it looks like parallel. If you apply Kirchoff's Loop Law, you will see that they are in series. And in that way too, you will get that answer. Hope that helps.
NO. The Capacitors are in series as when we go from one capacitor to another we find no junction in between.