Partially Filled Capacitor
A capacitor is an electrical device that stores energy. Between its two plates a capacitor can be filled with some material or evacuated to leave a vacuum. A partially filled capacitor is equivalent to two capacitors connected in a series, one with the material and the other empty.
The capacitance is
where is the percentage of the capacitor filled, the separation between the original plates, the dielectric constant, and the permittivity in a vacuum. Simplifying,
In this example, and .