Dielectric breakdown is the phenomenon in which an insulating material (dielectric) suddenly becomes electrically conductive due to a high electric field. This breakdown is characterized by a rapid increase in current that can lead to the destruction of the material.
The mechanism of dielectric breakdown depends on the type of material being considered. Here are the breakdown mechanisms for solids, liquids, and gases:
Solid Dielectric Breakdown:
In solids, dielectric breakdown occurs due to the formation of conductive paths called “electronic traps.” These traps are created by impurities, defects, or other imperfections in the material’s crystal lattice. When a high electric field is applied to the material, the electrons are accelerated and collide with these traps, generating free charge carriers that can flow through the material, leading to breakdown.
Liquid Dielectric Breakdown:
In liquids, dielectric breakdown occurs when the electric field is strong enough to ionize the liquid molecules, creating free electrons and ions. These free charge carriers can flow through the liquid and create a conductive path, leading to breakdown. This process is often accompanied by the formation of bubbles due to the heating of the liquid, which can further disrupt the dielectric properties of the liquid.
Gas Dielectric Breakdown:
In gases, dielectric breakdown occurs when the electric field is strong enough to ionize the gas molecules. This ionization leads to the formation of a plasma, which is a gas consisting of free electrons and ions. The plasma can conduct electricity and create a conductive path, leading to breakdown. The mechanism of gas breakdown is often associated with the Paschen’s law, which describes the minimum voltage required to cause breakdown in a gas at a given pressure and distance.
In summary, dielectric breakdown is a phenomenon that occurs when an insulating material is subjected to a high electric field, causing it to become conductive. The breakdown mechanism depends on the type of material being considered and can involve the creation of free charge carriers or the ionization of the material.
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