Spherical and Conical capacitor || Applications of Laplace's equation for capacitance calculation

In this video, Application of Laplace's equation is discussed and it is applied to calculate capacitance of the Spherical and Conical capacitor.

[aryanshah]

Sir will these be valid for any point inside the cone ??i think not as field lines will not be symmetric

[abhaya]

Question is,
How to find spherical capacitance Using solution of V from cylindrical coordinate system
i.e. V =Vo(ln(rho/b))/ln(a/b)
??

[aka]

and what if charge density doesnt equal zero in poissons equatoin