Capacitor Energy Storage Calculator
Calculate the energy stored in a capacitor from capacitance and voltage.
Shows energy in joules and charge in coulombs.
Energy Stored
A capacitor stores energy in its electric field between the plates. The stored energy and charge are:
E = ½CV² Q = CV
Where:
- E = Energy in joules (J)
- Q = Charge in coulombs (C)
- C = Capacitance in farads (F)
- V = Voltage across the capacitor (V)
Key observations:
- Energy scales with the square of voltage — doubling voltage quadruples stored energy
- This is why high-voltage capacitors are so dangerous — 400 V × 100 μF = ½ × 0.0001 × 160,000 = 8 joules, enough to cause a severe shock
Comparison with inductors:
- Capacitor stores energy in electric field: E = ½CV²
- Inductor stores energy in magnetic field: E = ½LI²
- They are the “dual” of each other in circuit theory
Practical examples:
| Application | Capacitance | Voltage | Energy |
|---|---|---|---|
| Camera flash | 100 μF | 300 V | 4.5 J |
| Car audio capacitor | 1 F | 12 V | 72 J |
| Supercapacitor (EV braking) | 3000 F | 2.7 V | 10,935 J ≈ 3 Wh |
| Defibrillator | 30 μF | 5000 V | 375 J |
| Laptop battery (comparison) | — | — | ~50,000 J = 14 Wh |