Capacitance and inductance
Capacitance and charge
- where
- charge (C)
- capacitance (F)
- voltage (V)
Explain this equation
Works out the charge stored on a capacitor at a given voltage. Useful in capacitor sizing and timing work.
Q is the stored charge in coulombs. C is the capacitance in farads: how much charge the capacitor holds per volt. V is the voltage across its terminals.
Capacitance is defined as charge per volt, so charge is simply capacitance times voltage. Higher voltage pushes more charge onto the plates.
Sense check: 100 µF at 12 V stores 0.0012 C. Double the voltage and the charge doubles.
Watch out: pick the right unit for C, as µF and F differ by a million. A capacitor can hold its charge after the supply is off.
A capacitor stores separated charge. Its capacitance relates stored charge to the voltage across it.
Convert microfarads to farads before multiplying. Capacitor voltage can remain after the supply is removed; a calculation is not proof of discharge.
Enter your values to see the result.
Common mistake
Leaving capacitance in μF but labelling the answer C.
Limits
Ideal fixed capacitor.
Sources
The tools calculate the displayed equation. They do not automatically choose cable sizes, approve installations, supply current regulatory tables, certify equipment or replace inspection and testing.