Charge Equation - Capacitors & Stored Charge Step by Step

The relation Q = C V turns capacitance and voltage into stored charge. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Capacitance converts voltage to charge

Capacitance tells how many coulombs are stored per volt.

Q = C V

Substitute exact values

Use 2 farads and 6 volts.

Q = 2\ \text{F}\cdot 6\ \text{V}

Multiply

The capacitor stores 12 coulombs.

Q = 12\ \text{C}

Capacitance is charge per volt

Hold voltage at 6 volts. Larger capacitance stores more charge at that same voltage.

\begin{array}{c|c|c}C&V&Q\\1\ \text{F}&6\ \text{V}&6\ \text{C}\\2\ \text{F}&6\ \text{V}&12\ \text{C}\\3\ \text{F}&6\ \text{V}&18\ \text{C}\\\end{array}

Voltage is the other direct direction

Now hold capacitance at 2 farads. The charge changes in the same ratio as the voltage.

\begin{array}{c|c|c}C&V&Q\\2\ \text{F}&3\ \text{V}&6\ \text{C}\\2\ \text{F}&6\ \text{V}&12\ \text{C}\\2\ \text{F}&9\ \text{V}&18\ \text{C}\\\end{array}