At fixed voltage, capacitance controls both stored charge and stored energy through exact row-by-row budgets. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Hold voltage fixed and scan capacitance

Keep the source voltage fixed at 6 volts. A larger capacitance stores more charge at the same voltage, and the energy ledger rises with the same capacitance factor.

Q=CVU=12CV2Q=CV\qquad U=\tfrac{1}{2}CV^{2}
Fixed-voltage capacitorThe checked capacitor is the middle table row.2 F

The charge and energy columns rise together

Read each row left to right: capacitance times the fixed voltage gives charge, then one-half capacitance times voltage squared gives stored energy.

CVQU1 F6 V6 C18 J2 F6 V12 C36 J4 F6 V24 C72 J\begin{array}{c|c|c|c}C&V&Q&U\\1\ \text{F}&6\ \text{V}&6\ \text{C}&18\ \text{J}\\2\ \text{F}&6\ \text{V}&12\ \text{C}&36\ \text{J}\\4\ \text{F}&6\ \text{V}&24\ \text{C}&72\ \text{J}\\\end{array}
Fixed-voltage capacitorThe middle table row matches the displayed capacitor.2 F

The checked row closes before rendering

The middle row is not a caption estimate. Its displayed capacitance, charge, voltage, and energy are the same checked quantities used by the table.

C=2 FQ=12 CU=36 JC=2\ \text{F}\qquad Q=12\ \text{C}\qquad U=36\ \text{J}
Fixed-voltage capacitorThe checked capacitor carries the middle-row value.2 F