All About the Surface of a Conductor

Insulators are materials that have low conductivity of electric current. Electrons can move from atom to atom in materials known as conductors. In insulators, the outer electrons are firmly bound to their respective nuclei. However, this is not the case in conductors, as electrons are not inbound. Notably, the surface of a charged conductor is equipotential. In this article, we discuss the distribution on the surface of conductors and the types of polarisation. This will help you understand that the surface of a charged conductor is equipotential.

The Meaning of Equipotential

 As already discussed above, the surface of a charged conductor is equipotential. To understand this, imagine electric potentials or voltages. Now, consider an isolated positive point charge as well as its radiating electric field lines. The radiation of these lines takes place out from a positive charge and their termination happens on negative charges.

At certain places, the electric potential is constant. Experts refer to these surfaces as equipotential surfaces. These are either three dimensional or two dimensional structures. Thus, the surface of a charged conductor is equipotential. The term equipotential is used by experts to refer to an equipotential line.

The equipotential lines shall be perpendicular to electric field lines. This is an important rule due to which the surface of a charged conductor is equipotential.

Charge Distribution on the Surface of Conductors

The charge distribution on the surface of conductors is of the following two types:

Charge distribution in a regularly shaped conductor:

Conductors allow charges to move around due to the presence of highly mobile charge carriers (electrons). If the conductor’s surface is regularly shaped like a sphere, the charges will push each other until they end up at the same distance.

Charge distribution in an irregularly shaped conductor:

If the surface of the conductor is irregularly shaped, there would be more charge at the sharp curving of the surface.  Moreover, where there is a less curved surface, there would be a smaller buildup of charge. Thus, large electric fields shall appear near these sharper points.

Various Types of Polarisation

Below are the various types of polarisation that impact the distribution on the surface of conductors.

Space Charge (or Interfacial) Polarisation: In ceramics, this phenomenon occurs from extraneous charges that arise due to contaminants or irregular geometry. This takes place in the interfaces of the polycrystalline solids.

Ionic Polarisation: In ionic solids, for example, ceramic materials, there is a symmetrical arrangement in a crystal lattice with a polarisation that is net-zero. The anions and cations move in opposite directions on applying an electric field, creating a relatively large ionic displacement.

Dipole (or Orientation) Polarisation: Certain types of solids have permanent molecular dipoles. In an electric field, such solids rotate in the direction of the applied field, creating a net average dipole moment per molecule.

Electronic Polarisation: This occurs in all atoms affected by an electric field application. The atom’s nucleus and its electron cloud’s centre may move away, creating a tiny dipole with a minimal polarisation effect.

Conclusion

Insulators are materials with poor conductivity of electric current. However, in conductors, the electrons are free to move from atom to atom in materials. Hence, they have good conductivity. The surface of a charged conductor is equipotential. Moreover, the charge distribution in a regularly shaped conductor differs from that in an irregularly shaped conductor. The four types of polarisation are space charge (or interfacial) polarisation, ionic polarisation, dipole (or orientation) polarisation and electronic polarisation.