capacitor: a device that stores electric charge capacitance: amount of charge stored per unit volt dielectric: an insulating material dielectric strength: the maximum electric field above which an insulating material begins to break down and conduct parallel plate capacitor: two identical conducting plates separated by a distance
An electric field is created between the plates of the capacitor as charge builds on each plate. Therefore, the net field created by the capacitor will be partially decreased, as will the potential difference across it, by the dielectric.
A parallel plate capacitor with a dielectric between its plates has a capacitance given by \ (C=\kappa\epsilon_ {0}\frac {A} {d}\\\), where κ is the dielectric constant of the material. The maximum electric field strength above which an insulating material begins to break down and conduct is called dielectric strength.
Why can we consider a capacitor with mixed dielectrics equivalent to two series or parallel capacitors? When a parallel-plate capacitor has two different dielectrics as shown below, it can be considered equivalent to two capacitors in series, one taking the value of one of the dielectrics and the other of the other dielectric.
Let us first suppose that two media are in series (Figure V. V. 16). Our capacitor has two dielectrics in series, the first one of thickness d1 d 1 and permittivity ϵ1 ϵ 1 and the second one of thickness d2 d 2 and permittivity ϵ2 ϵ 2. As always, the thicknesses of the dielectrics are supposed to be small so that the fields within them are uniform.
There is another benefit to using a dielectric in a capacitor. Depending on the material used, the capacitance is greater than that given by the equation C = εA d by a factor κ, called the dielectric constant. A parallel plate capacitor with a dielectric between its plates has a capacitance given by C = κε0A d(parallelplatecapacitorwithdielectric).