25.6: Energy Stored in a Capacitor: Problem Solving
In 1749, Benjamin Franklin coined the word battery for a series of capacitors connected to store energy. Capacitors store electric potential energy that can be released over a short time. This property means capacitors have a wide range of applications.
Capacitor-discharge ignition is a type of ignition system commonly found in small engines where the energy released from a capacitor ignites an induction coil that, in turn, fires the spark plug.
To calculate the energy stored in a capacitor of a typical CDI system, at least two of the following parameters should be known:
- The voltage applied across the capacitor
- The charge stored in the capacitor
- The capacitance of the capacitor
Since these three parameters are related by the equation given below, the unknown parameter can be calculated if any two parameters are known:
For any given case, the potential energy stored can be calculated using the values of capacitance, voltage, and charge:
