Capacitor Energy Calculator
An interactive tool to calculate the energy stored in a capacitor and explore the underlying principles of electronics.
Calculate Stored Energy
in Joules (J)
Based on the formula: E = ½ * C * V²
Understanding the Concepts
Capacitors store energy in an electric field. This section breaks down the key components of the calculation.
The energy stored in a capacitor is the potential energy held within the electric field between its conductive plates. When a voltage is applied across the capacitor, electric charge accumulates on the plates—positive charge on one and negative on the other. Work must be done to move these charges against the electric field, and this work is stored as electrical potential energy.
This stored energy can be released quickly, which is why capacitors are essential in applications like camera flashes, power supply smoothing, and energy backup systems. The amount of energy a capacitor can store is directly proportional to its capacitance and to the square of the voltage applied across it.
Interactive Visualization
See how voltage impacts stored energy in real-time. Adjust the slider to see the exponential relationship described by the formula E = ½CV².
Frequently Asked Questions
The standard (SI) unit for energy is the Joule (J). Regardless of the units used for capacitance or voltage in the calculation, the resulting energy is typically converted to Joules for consistency.
The factor of ½ comes from the fact that the voltage across the capacitor increases from 0 to its final value V as it charges. The energy stored is the integral of voltage with respect to charge (∫V dq). Since V = Q/C, this becomes ∫(Q/C) dQ, which evaluates to Q²/2C. Substituting Q = CV gives ½CV². Essentially, the energy is based on the average voltage during the charging process (V/2), not the final voltage.
Ideally, yes. However, real-world capacitors have some internal "leakage" resistance, which causes the stored charge to slowly dissipate over time, leading to a gradual loss of energy. The rate of leakage depends on the quality and type of the capacitor's dielectric material. High-quality capacitors can hold a charge for a very long time.
