A parallel-sharing-conserves-charge scan holds the two capacitances fixed and varies the source voltage across three rows, checking that total charge Q_total = C_a * V_a + C_b * V_b reappears as the shared voltage V_f = Q_total / (C_a + C_b) row by row. The arithmetic is exact only for the stated capacitances, voltages, charges, and rows in the ideal capacitor and ideal-switch model. Real circuits add ESR, switch on-resistance, parasitics, dielectric loss, switching-timing errors, probe/calibration limits, finite precision, and measurement uncertainty.
Parallel connection makes one final voltage from total 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
Two parallel capacitors first contribute source charges
The final voltage is downstream of the two source snapshots, not an independent label.
54C+0C=54C
The final voltage tracks total starting charge
The capacitances stay fixed; only the first capacitor's initial voltage changes.
Va3V6V9VQtotal18C36C54CVf2V4V6V
Parallel sharing conserves total charge
The final voltage is total charge divided by total capacitance, not a hand-authored label.