Capacitors in Parallel - Electric Fields, Electrostatics & Capacitors Step by Step

This capacitors-in-parallel lesson treats shared voltage as the reason ideal capacitances add across the same two nodes. The 2 F plus 3 F row gives 5 F exactly only for the stated ideal parallel topology. Real capacitors have tolerance, dielectric behavior, ESR and ESL, leakage, voltage dependence, calibration limits, finite precision, and measurement uncertainty.

Parallel capacitors share voltage, so their charge capacities add. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Parallel capacitors share voltage

Parallel capacitors connect to the same two nodes, so they share voltage.

V_a = V_b

Add capacitances in parallel

The capacitances are 2 farads and 3 farads.

C_{\text{eq}} = 2\ \text{F} + 3\ \text{F}

Compute equivalent capacitance

The equivalent capacitance is 5 farads.

C_{\text{eq}} = 5\ \text{F}

Parallel addition keeps adding storage

Each row connects two capacitors across the same buses. The diagram shows the middle row, where direct addition gives the equivalent capacitance.

\begin{array}{c|c|c}C_a&C_b&C_{\text{eq}}\\1\ \text{F}&2\ \text{F}&3\ \text{F}\\2\ \text{F}&3\ \text{F}&5\ \text{F}\\3\ \text{F}&4\ \text{F}&7\ \text{F}\\\end{array}