Factors on which capacity of a conductor depends
According to the definition of capacitance, C = Q/V. So for a fixed amount of charges, the factors on which potential of a conductor change, capacitance also will change for those factors. Followings are the causes of change:
(a) Area of the conductor: The more the area increases, more will be the increase in capacitance. We know for a spherical conductor, C = 4πε0εrr. So as r increases, so area also increases, along with it capacitance C also will increase. It is generally true for all conductors.
(b) Medium surrounding the conductor: Capacitance of a conductor depends on the dielectric constant of the medium surrounding it. The capacitance of a conductor is more of the medium having higher dielectric constant and capacitance will be less for the medium having lower dielectric constant. If the capacitance of a conductor in air medium or in vacuum is C0 and it is Ck for a medium of dielectric constant εr then from equation (Capacitance of a capacitor) it can be shown that,
εr = Ck/C0
= [Capacitance of a conductor in any medium / Capacitance of that conductor in air or in vacuum]
(c) Separation between the plates: a Capacitance decrease due to the increase of separation between the plates of a parallel plate capacitor and reverse is true when separation decreases.
(d) Presence of the conductor with any other conductor or grounded conductor: If there exists any other changeless or grounded conductor with the charged conductor, then due to electrical induction, capacitance of the experimental conductor will increase. But if a similarly charged body is present near the charged conductor, capacitance of the experimental conductor will decrease and if oppositely charged body is present then capacitance will increase.