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. Since the work done to charge the capacitor is given by the product of the charge supplied by the battery and the potential difference of the battery provides a constant flow of charge and constant potential difference. However, as the potential difference across the capacitor changes as the charge stored in the capacitor changes. This provides a maximum efficiency of 50% to capacitors which is far less than the 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

𝐶 is the capacitance of the capacitor

and