Frequently Asked Questions
How much energy does a capacitor store?
E = ½·C·V², so energy rises with the square of the voltage - doubling voltage quadruples stored energy.
What is the stored charge?
Q = C·V; this calculator reports both the charge in coulombs and the energy in joules.
Why does voltage matter more than capacitance?
Because energy is linear in C but quadratic in V, raising voltage is the most effective way to store more energy (within the rated limit).
Where is this used?
Camera flashes, defibrillators, power-supply smoothing, and energy-recovery systems all rely on stored capacitor energy.
How do I calculate energy from charge instead of voltage?
Use E = Q² ÷ (2C), the same energy written in terms of charge. It follows from E = ½CV² by substituting V = Q/C, so all three forms - ½CV², ½QV, and Q²/(2C) - give the identical result. Use whichever pair of quantities you already know.
How do I safely discharge a capacitor?
Never short the terminals with a bare screwdriver on a large or high-voltage capacitor - the sudden current can arc, weld, or damage the part, and the shock can be dangerous. Instead discharge through a resistor: touch a suitably rated resistor (for example a few hundred ohms to a few kilohms, rated for the energy) across the terminals for several seconds, then verify the voltage has dropped to a safe level with a meter. Large capacitor banks in flashes, defibrillators, and power supplies can hold a lethal charge long after power is removed, so always confirm zero volts before handling.
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Estimates for informational purposes only.
Important Disclaimer: Estimates for informational purposes only.
This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.