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Consider a coaxial cable of the type used in cable television systems. It consists of a cylindrical core wire inside a hollow metallic cylinder that serves as an outer conductor/shield. Dielectric insulating layer fills the void between the conductors. The core wire and cylindrical shield are aligned on the same central axis, hence the name co-axial. plastic jacket dielectric insulator metallic shield centre core The electric potential (voltage) inside the dielectric layer obeys the Laplace Equation in cylindrical coordinates (r,0,z) : V-V =0 Here, z > 0, 0