The energy stored in a charged capacitor can be expressed using the formula:

where:

• $E$ is the energy stored,
• $C$ is the capacitance of the capacitor, and
• $V$ is the voltage across the capacitor.

When a capacitor is charged, it accumulates electrical energy within its electric field. The amount of energy that a capacitor can store is determined by both its capacitance and the voltage applied across it.

Capacitance is defined as the ability of a capacitor to store electric charge. It is quantitatively expressed as the ratio of the charge stored on each plate of the capacitor to the voltage across those plates. The standard unit for capacitance is the farad (F). A capacitor that has a higher capacitance can store more charge, and consequently more energy, than one with a lower capacitance.

The voltage across a capacitor represents the potential difference between its two plates. As a capacitor charges, the voltage across it rises until it matches the voltage of the source supplying the charge. Notably, the energy stored in a capacitor is proportional to the square of the voltage. This means that if the voltage across the capacitor is doubled, the energy stored in it will increase by a factor of four.

In summary, the energy stored in a charged capacitor is described by the formula:

This indicates that the energy depends on both the capacitance of the capacitor and the voltage across it, with energy being proportional to the square of the voltage.