The capacitance of a parallel-plate capacitor is given by C=ε/Ad, where ε=Kε 0 for a dielectric-filled capacitor. Adding a dielectric increases the capacitance by a factor of K, the dielectric constant. The energy density (electric potential energy per unit volume) of the electric field between the plates is:
Change the size of the plates and add a dielectric to see the effect on capacitance. Change the voltage and see charges built up on the plates. Observe the electrical field in the capacitor. Measure the voltage and the electrical field. A capacitor is a device that stores an electrical charge and electrical energy.
where A is the area of the plate . Notice that charges on plate a cannot exert a force on itself, as required by Newton’s third law. Thus, only the electric field due to plate b is considered. At equilibrium the two forces cancel and we have The charges on the plates of a parallel-plate capacitor are of opposite sign, and they attract each other.
The magnitude of the electrical field in the space between the plates is in direct proportion to the amount of charge on the capacitor. Capacitors with different physical characteristics (such as shape and size of their plates) store different amounts of charge for the same applied voltage V across their plates.
To see how this happens, suppose a capacitor has a capacitance C 0 when there is no material between the plates. When a dielectric material is inserted to completely fill the space between the plates, the capacitance increases to is called the dielectric constant. In the Table below, we show some dielectric materials with their dielectric constant.
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.