What is capacitance?
Capacitance is the ability of a component to store electrical charge. For a parallel plate capacitor, it depends on the plate area, the separation between the plates, and the dielectric material between them. It is measured in Farads (F), though practical values are usually in picofarads (pF) or microfarads (µF).
How do I calculate the capacitance of a parallel plate capacitor?
Use the formula C = ε₀ × K × A / d, where ε₀ is the permittivity of free space (8.854 × 10⁻¹² F/m), K is the dielectric constant of the material, A is the overlapping plate area in m², and d is the distance between the plates in meters. This calculator applies that formula automatically.
What is the capacitance of two plates with A = 1 m² separated by 1 mm (air)?
Using the formula with K ≈ 1.00054 for air, ε₀ = 8.854 × 10⁻¹² F/m, A = 1 m², and d = 0.001 m, the capacitance is approximately 8.859 nF (about 8,859 pF).
What is the difference between a capacitor and capacitance?
A capacitor is a physical electronic component designed to store and release electrical energy. Capacitance is the property that describes how much charge a capacitor can store per unit of voltage. In short, a capacitor is the device, and capacitance is its measurable characteristic.
What does the dielectric constant (K) represent?
The dielectric constant, or relative permittivity, is a dimensionless number that describes how well an insulating material can store electrical energy compared to a vacuum (K = 1). Materials like glass (K ≈ 4.7) or rubber (K ≈ 7) increase capacitance because they allow more charge storage for the same geometry.
Why does increasing the plate area increase capacitance?
Larger plate area allows more electric field lines to form between the plates, which means more charge can be stored at the same voltage. Capacitance scales linearly with plate area — doubling the area doubles the capacitance.
Why does increasing the separation distance decrease capacitance?
A greater separation weakens the electric field between the plates, reducing the amount of charge that can be maintained at a given voltage. Capacitance is inversely proportional to plate separation — doubling the distance halves the capacitance.
Can parallel plate capacitors be used in PCB design?
Yes. Small-value capacitors can be etched directly into a PCB for RF applications by using two copper traces as plates with the board substrate (e.g. FR4, K ≈ 4.2) as the dielectric. However, for most applications it is more practical and cost-effective to use discrete surface-mount capacitors.