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# Capacitance of parallel plate capacitor

Source: Company Dynamics Editor: PingShang Click: Release time: 2021-03-11 08:45:52

The capacitance of a parallel plate capacitor is proportional to the area A (in meters 2) of the smallest of the two plates, and is proportional to the distance or spacing d (that is, the thickness of the dielectric) between the two conductive plates in meters. Inversely. The general formula for the capacitance of a parallel plate capacitor is: C = ε (A / d) where ε represents the absolute permittivity of the dielectric material used. The dielectric constant, ε? Is also called the "dielectric constant of free space", which has a constant value of 8.84×10 -12 farads per meter.

To make the mathematics easier, the free space permittivity εo can be written as: 1/(4πx 9×10 9), or picofarad per meter (pF) unit can be used as a constant. Given: a free space value of 8.84. Please note that despite this, the final capacitance value will be in picofarads instead of farads.

Usually, the conductive plates of a capacitor are separated by some kind of insulating material or gel, rather than by an ideal vacuum. When calculating the capacitance of a capacitor, we can consider that the dielectric constant of air, especially dry air, is the same as the permittivity of vacuum because they are very close.