Capacitors in Series and Parallel

Parallel capacitors sit between the same two voltage nodes, so each one feels the identical voltage from the battery. Each plate pair adds its own area to store charge, so the total charge is just the sum of each capacitor's charge: Q_total = Q1 + Q2 + Q3. Since Q = CV and V is the same for all, the capacitances simply add: C_eq = C1 + C2 + C3. It behaves like one capacitor with bigger plates because, electrically, that's exactly what it is.

Series capacitors form a chain, one after another, with no other path for charge to go. When the battery pushes charge onto the first plate, that charge has nowhere to come from except being pulled off the facing plate of the next capacitor, which pulls from the next, and so on. So every capacitor in the chain ends up with the exact same charge Q, even if their capacitances differ wildly. The battery's voltage splits across them instead: V_total = V1 + V2 + V3 = Q/C1 + Q/C2 + Q/C3 = Q(1/C1 + 1/C2 + 1/C3), which gives 1/C_eq = 1/C1 + 1/C2 + 1/C3.

This mirrors resistors, but flipped: resistors in series add directly and in parallel add as reciprocals, while capacitors do the opposite. That contrast is worth holding onto going into circuits that mix both, since the same same-charge and same-voltage reasoning is what you'll use to find charge and voltage at every junction.