Write down the formula for the electrical capacity of a flat capacitor.

The simplest capacitor is a system of two flat conducting plates located parallel to each other at a small distance compared to the dimensions of the plates and separated by a dielectric layer.
С = ε * ε0 * S / d, where ε is the dielectric constant of the dielectric, ε0 is the electric constant 8.85 · 10−12 F / m, S is the area of the plates, d is the distance between the plates.