A Co-axial cable is a Transmission line, in which two conductors are placed co-axially and are separated by some dielectric material with dielectric constant (or) permittivity ( ).

a conductor is in the form of a cylinder with some radius, let the radius of inner conductor is ‘a’ meters and that of outer conductor be ‘b’ meters.

Now connect this co-axial conductor to a supply of ‘V’ volts , after applying ‘V’ assume positive charges are distributed on and negative charges on .

Now, a field is induced between and because of flux lines, to find out at any point P between these two conductors

location of P is out of the conductor an inside the conductor .

.

assume a cylindrical co-ordinate system and axis of cable coincides with z-axis this is similar to a line charge distribution placed along the z-axis.

.

.

.

.

.

.

.

.

.

.

L- length of the conductors.

b-radius of the outer conductor.

a- radius of the inner conductor.

– permittivity of the medium.