Capacitor Energy

Key Stage 5

Capacitor energy refers to the energy stored in a capacitor due to the separation of charge.

Energy stored in a capacitor can be used in various applications like powering the lights designed to flash and providing energy for defibrillators.
Capacitors store energy in the electric field between their plates.
The stored energy is released when the capacitor is discharged.
Capacitors can deliver energy quickly compared to batteries.
Used in power supplies to smooth out fluctuations in voltage.
The energy stored in a capacitor is half the energy required to charge the capacitor. The energy required to charge the capacitor is the work done by the battery which is given by the product of the charge supplied by the battery and the potential difference of the battery since the battery provides a constant flow of charge and constant potential difference. However, as the potential difference across the capacitor changes with the charge stored in the capacitor so the energy stored by a capacitor is half the product of the charge and potential difference.
The maximum possible efficiency of a capacitor is 50% which is far less than the maximum theoretical efficiency of a battery.

The energy, 𝐸, stored in a capacitor is given by any of the three following formulae:

•\(𝐸 = \frac{1}{2}𝐶𝑉^2\)

•\(𝐸 = \frac{1}{2}Q𝑉\)

•\(𝐸 = \frac{1}{2}\frac{Q^2}{C}\)

Where:

𝐸 is the energy stored in the capacitor

and