Parallel Plate Capacitor

What is Parallel Plate Capacitor?

It is an arrangement used for storing electric charge and hence electric energy.

Principle of Parallel Plate Capacitor:

When we bring uncharged earth connected rod near the charged rod, the capacity of the charged rod increases.

Construction and Theory of Parallel Plate Capacitor:

parallel plate capacitor diagram - Parallel Plate Capacitor

It consists of two plates X and Y, held parallel with each other. The area of each plate is ‘A’ and the distance between them is ‘d’. Plate Y is earth connected and X plate is fully charged.

Plate X is given +Q charge, due to the phenomenon of induction -Q charge is induced on the inner side of plate Y. Due to this electric field E is set up between the plates which are given by-

E = σ0
Where σ is surface charge density and (σ = Q/A)
⇒ E = Q/Aε0
But we know,
V = E x d = Q/Aε0 x d
The capacity of parallel plate capacitor is given by-
C = Q/V = Q x Aε0/Qd
⇒ C = Aε0/d ……………….(I)

Hence the capacity of the capacitor depends upon the following three factors-

  • Area of plates.
  • Distance between plates.
  • Nature of medium separating the two plates.

When the plates of the capacitor are separated by some dielectric medium (like mica sheet) of dielectric constant K or relative permittivity εr, then-

Cm = KAε0/d = Aε0εr/d ……………..(II)
From (I) and (II)-
Cm = K x C

i.e. capacity becomes K times capacity with air/Vaccum as the dielectric.


Resistance and Resistivity of a ConductorDerivation of de-Broglie equation
Coulomb’s LawStructures of Simple Ionic Compounds
Capacitor and its PrincipleElectrochemical Series and its Applications
Uses of Electromagnetic WavesAcids and Bases– Tamil Board

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