When capacitors are connected in series, their individual capacitance values contribute to the total equivalent capacitance. The series connection is achieved when the positive plate of one capacitor is connected to the negative plate of the subsequent capacitor. This forms a continuous path for current flow, creating a series circuit.
Figure 8.3.1 8.3. 1: (a) Three capacitors are connected in series. The magnitude of the charge on each plate is Q. (b) The network of capacitors in (a) is equivalent to one capacitor that has a smaller capacitance than any of the individual capacitances in (a), and the charge on its plates is Q.
However, if you have a series of capacitors, when you charge the first plate all the others charge up with the same or opposite charge -by induction- in a sort of chain reaction: you can imagine that the effort (that is the potential) to keep all that charge in place is magnified.
On the whole, capacitors in series summary can be stated as that the entire capacitance value of the circuit having series-connected capacitors equals the reciprocal of the sum of each capacitor in the connection. Please refer to this link to know more about Capacitor MCQs.
Then we can see that if and only if the two series connected capacitors are the same and equal, then the total capacitance, CT will be exactly equal to one half of the capacitance value, that is: C/2.
With series connected resistors, the sum of all the voltage drops across the series circuit will be equal to the applied voltage VS ( Kirchhoff’s Voltage Law ) and this is also true about capacitors in series. With series connected capacitors, the capacitive reactance of the capacitor acts as an impedance due to the frequency of the supply.