What is a Parallel Plate Capacitor?
When two parallel plates are connected across a battery, the plates are charged and an electric field is established between them, and this setup is known as the parallel plate capacitor.
Parallel Plate Capacitor Formula
Where:
- ϵo is the permittivity of space (8.854 × 10−12 F/m)
- k is the relative permittivity of dielectric material
- d is the separation between the plates
- A is the area of plates
Parallel Plate Capacitor Derivation
- A parallel plate capacitor consists of two large plane parallel conducting plates separated by a small distance.
- Suppose two plates of the capacitor have equal and opposite charge Q on them. If A is the area of each plate then surface charge density on each plate is
- Suppose two plates of the capacitor have equal and opposite charge Q on them. If A is the area of each plate then surface charge density on each plate is
- We have already calculated field between two oppositely charged plates using Gauss’s law which is and in this result effects near the edges of the plates have been neglected
- Since electric field between the plates is uniform the potential difference between the plates is
where d is the separation between the plates.
- Thus, capacitance of parallel plate capacitor in vacuum is
- We see that quantity on which capacitance of parallel plate capacitor depends i.e.,ε0 , A and d are all constants for a capacitor.
- Thus we see that in this case capacitance is independent of charge on the capacitor but depends on the area of its plates and separation distance between the plates.
