Cylindrical capacitor
For a cylindrical geometry like a coaxial cable, the capacitance is usually stated as a capacitance per unit length.The charge resides on the outer surface of the inner conductor and the inner wall of the outer conductor.
It depends on the inner and outer radius.
Capacitance per unit length = 2 * π * (relative permittivity) * (permittivity of space) /Logarithm (outer radius / inner radius )
The equation is:
C =2 π k ϵ /Log(ro/ri)
Where:
C=Capacitance
ri=inner radius
ro= outer radius
k=relative permittivity
ϵ= permittivity of space
lets consider r= inner radius , R = outer radius , x = value of permitivity of space, k=relative permitivity
