# Why the charge in each capacitors plate are equal in magnitude in series combination?

Suppose two capacitors are connected in series, I understand that external plates gets equal magnitude because of the batteries terminals, but how does the internal plates also get the charge with same magnitude (opposite in nature). I read some answer saying that because the current flowing in the Series combination is same throughout the circuit. But then i am getting confused as to why current is flowing same throughout? Is there any other reason as to why internal plates gets the same magnitude of charge? I know that the internal plates gets charges because of induction of external plates charges but why in equal magnitude?

Suppose you have two capacitors in series like so:

————————||——————||————————
C1      C2


Consider only the central piece:

         |——————|
C1      C2


This is a isolated conductor, separated from the rest of the circuit by the insulating dielectric gaps in the capacitors. The total charge of an isolated conductor is a constant. If the initial state is that both capacitors are uncharged, and some external voltage is applied across the total series arrangement, the total charge on the isolated segment must stay at zero. Therefore any charge on the right-hand plate of C1 must be balanced by an equal and opposite charge on the left-hand plate of C2.

• Why internal plates gets the same charge 'in magnitude' as that of the external plates? Jun 25, 2022 at 17:08
• The total energy stored in an electric field goes roughly like the volume where the field is strong. A capacitor whose plates have equal charge has a strong field in the gap between the plates, but a capacitor whose plates have unequal charge has a “fringe field” which is non-negligible outside of the capacitor. Confining the field to the inside of each capacitor, by having equal charges on their plates, is the minimum-energy configuration.
– rob
Jun 25, 2022 at 17:14