Capacitors: Three Things that Affect Capacitance

Capacitors are electrical components that store and release electrical energy. They are commonly used in electronic circuits for a variety of purposes, such as filtering, coupling, and storing electrical energy storage. The capacitance of a capacitor, or its ability to store electrical energy, is determined by three physical factors:

1) The type of material used as an insulator (ε)
2) The area of the two conductive plates (A)
3) The distance between the two plates (d).

The type of material used as an insulator, or dielectric material, can significantly affect a capacitor’s overall capacitance value. Different materials have different dielectric constants (ε), which determine how effectively they can insulate the conductive plates and store electrical energy within a capacitor. Materials with higher dielectric constants, such as ceramics, mica, and polystyrene, typically result in higher capacitance values in electronic components.

The effective overlapping surface area of the conductive plates (A) also directly affects a capacitor’s capacitance. The larger the plate area, the more electrical energy the capacitor can store. However, increasing the surface area of the plates also increases the physical size and footprint of the capacitor, which may not be practical for compact or space-limited applications.

Parallel plate capacitor cross-section with plate area A and dielectric constant ε — Image by Fabian R.

The distance between the conductive plates (d), commonly referred to as plate separation or dielectric thickness, also plays a key role in determining a capacitor’s capacitance value. The closer the plates are positioned, the higher the resulting capacitance. On the other hand, increasing the plate separation can also increase the voltage rating of the capacitor, which refers to the maximum allowable voltage it can withstand before it breaks down, leaks, or fails.

In summary, the capacitance value of a capacitor is determined by: