Science & engineering
Capacitor charge sharing
Calculate the ideal final voltage when two charged capacitors are connected in parallel.
A clear answer. Here’s how.
Uses conserved signed charge: Vfinal=(C₁V₁+C₂V₂)/(C₁+C₂), with consistently labelled plate polarity. Reports initial/final stored energies and the energy difference dissipated or radiated during equalisation. The ideal final-state model does not predict peak current, transient ringing, polarity suitability, ESR or ratings.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- First capacitance (µF)
- 100
- First signed initial voltage (V)
- 5
- Second capacitance (µF)
- 100
- Second signed initial voltage (V)
- 0
Example result
- Final common voltage
- 2.5 V
- Total signed charge
- 0.0005 C
- Initial stored energy
- 0.00125 J
- Final stored energy
- 0.000625 J
- Equalisation energy difference
- 0.000625 J