Capacitor Energy Calculator
Compute energy stored in a capacitor: E = 0.5 × C × V^2.
Enter Values
Fill in the fields and press Calculate to see instant results.
What is the Capacitor Energy Calculator?
The Capacitor Energy Calculator computes the electrical energy stored in a charged capacitor. Energy storage in capacitors is fundamental to many applications including power supplies, flash photography, power factor correction, uninterruptible power supplies (UPS), and energy harvesting systems. Understanding capacitor energy helps engineers design systems that efficiently store and release electrical energy.
Formula
The energy stored in a capacitor is calculated using:
Where:
- E = Energy stored (measured in joules, J)
- C = Capacitance (measured in farads, F)
- V = Voltage (measured in volts, V)
Alternative formulas:
- E = 0.5 × Q × V (using charge Q)
- E = 0.5 × Q² / C
- E = 0.5 × C × V²
How to Use
- Enter the Capacitance (C) in farads (F)
- Enter the Voltage (V) in volts (V)
- Click Calculate
- The calculator displays the Energy (E) in joules (J)
Worked Example
Given:
- Capacitance (C) = 1,000 μF (0.001 F)
- Voltage (V) = 50 V
Calculation:
E = 0.5 × C × V² = 0.5 × 0.001 F × (50 V)²
E = 0.5 × 0.001 × 2,500 = 1.25 joules
Interpretation: The capacitor stores 1.25 joules of energy
Note: Doubling voltage to 100V would store 5 joules (4× energy)
Real-World Applications
- Flash Photography: Camera flash capacitors store energy for high-power brief pulses
- Uninterruptible Power Supply (UPS): Backup capacitors provide brief power during transitions
- Energy Harvesting: Estimate energy available from environmental energy collection
- Power Factor Correction: Capacitors store and release reactive energy to stabilize grid
- Ride-Through Circuits: Maintain power during brief voltage dips or power supply transitions
Energy Comparison (at Different Voltages)
- 1 F capacitor: At 10V stores 50 J; at 100V stores 5,000 J
- 1,000 μF capacitor: At 50V stores 1.25 J; at 100V stores 5 J
- Camera flash capacitor (150 μF at 330V): Stores ~8.15 J of energy
- Supercapacitor (3000 F at 2.7V): Stores ~10,935 J of energy
Key Definitions
- Energy (E): Capacity to do work, measured in joules (J); 1 J = 1 watt × 1 second
- Joule (J): SI unit of energy and work; the energy delivered by 1 watt of power for 1 second
- Capacitor: Two-terminal device that stores electrical energy in an electric field
- Capacitance (C): Measure of capacitor's ability to store charge, in farads (F)
- Voltage (V): Electrical potential difference across capacitor plates
- Dielectric Strength: Maximum voltage per unit distance a dielectric can withstand without breakdown
Frequently Asked Questions
Why is energy proportional to voltage squared?
Energy depends on both stored charge (Q = C × V) and voltage. Since both increase with voltage, the result is quadratic: E = 0.5 × C × V². Doubling voltage quadruples stored energy.
How much energy does a typical supercapacitor store?
A 3000 F supercapacitor at 2.7V stores approximately 10,935 joules. This is thousands of times more than conventional capacitors but still modest compared to batteries for long-term storage.
What is the energy in a camera flash capacitor?
Typical camera flash capacitor: 150 μF at 330V stores approximately 8.15 joules. This energy delivers a brief intense light pulse lasting milliseconds.
Can capacitors replace batteries?
Capacitors store less energy than batteries for the same volume and weight. However, capacitors can charge/discharge much faster and support higher peak currents, making them ideal for power bursts and energy harvesting.
How does temperature affect stored energy?
Temperature doesn't directly affect stored energy at a given voltage, but it affects capacitance. Higher temperature typically decreases capacitance in most dielectric materials, reducing energy storage capacity.
What happens if a charged capacitor discharges through a resistor?
Stored energy is dissipated as heat in the resistor according to the RC time constant (τ = R × C). All energy eventually converts to heat: E = 0.5 × C × V² over time approximately 5τ.