GALAXY

PARALLEL PLATE CAPACITOR

A parallel plate capacitor consists of two conducting plates of same dimensions. These plates are
placed parallel to each other. Space between the plates is filled with air or any insulating material (dielectric). One plate is connected to positive terminal and other is connected to negative term-
inal of power supply. The plate connected to positive terminal acquires positive charge and the
other plate connected to negative terminal acquires equal negative charge .The charges are stored between the plates of capacitor due to attraction.

DEPENDENCE OF CHARGE STORED IN A CAPACITOR

Electric charge stored on any one of the plates of a capacitor is directly proportional to the potential difference between the plates. i.e.,

Q a V
OR
Q = (constant) V
Q = CV
Where C = capacitance of capacitor

CAPACITANCE OF A PARALLEL PLATE CAPACITOR

Let The area of each plate = A
The separation between plates = d
Medium = air
Surface density of charge on each plate = s
The electric field intensity between the plates of capacitor is given by

E = s / eo

Potential difference between the plates of capacitor can be calculated by the following relation

V = Ed

Putting the value of "E"

V = (s/eo) x d

But s = Q/A

V = Qd/A.eo

AeoV = Qd…………(a)

We know that
The electric charge stored on any one of plate of capacitor is

Q = CV……………(b)

Putting the value of Q in (a)

AeoV = CVd

Cd = Aeo

C = Aeo/d