Capacitors in Parallel

In a parallel combination, capacitors $C_1, C_2, C_3, \ldots$ are connected between the very same pair of points -- all their "left" plates joined to one common node, and all their "right" plates joined to another common node -- with the source of potential difference $V$ connected directly across these two shared nodes.

Same voltage across every capacitor. Since every capacitor's two plates are tied directly to the same pair of nodes as every other capacitor's plates, and all points on one node are at one common potential while all points on the other node are at another common potential, every capacitor in a parallel combination experiences exactly the same potential difference $V$, equal to the source voltage.

Charges add. Each capacitor, subjected to the same $V$, carries its own charge $Q_i = C_iV$, and the TOTAL charge supplied by the source is the sum of these individual charges (charge conservation at each shared node):

Defining the equivalent capacitance $C_p$ by $Q = C_pV$, and comparing directly,

so, unlike the series case, the equivalent capacitance for a PARALLEL combination is found by simple, direct addition of the individual capacitances -- no reciprocals involved. …