Question

a) Explain what happens inside a dielectric material at the molecular level in the presence of an external electric field E, b) When studying electrostatics we come to the conclusion that in equilibrium there is no electric field inside a conductor. How is it that now that there is an electric current inside the conductor, one can already speak of the presence of an internal electric field (inside a conductor)?

Answer 1

(a) In the presence of external electric field, the polar or non polar molecules of the dielectric gets polarized to develop a net dipoles. The dipoles have a tendency to align in the external electric field. Therefore, an internal electric field gets established, in opposite direction to the external electric field. As a result, net electric field becomes weak inside the dielectric.

(b) Although in conductors, there no net electric field, but this happens only when conductor achieve electrostatic equilibrium, when charge inside the conductor distributes itself in such a way so as to nullify the external electric field.

But, when electric current is established in a conductor due to the applied voltage, the conductor is not in electrostatic equilibrium. Rather, the conductor is constantly under the process to achieve electrostatic equilibrium by movement of charge to establish electric current