Dielectric breakdown occurs when an insulating material, or dielectric, becomes conductive due to a strong electric field. This happens when the electric field strength exceeds the material's ability to resist the flow of electric current, causing it to fail. As a result, the material can no longer insulate, leading to a sudden surge of electricity. This phenomenon is commonly observed in gases, liquids, and solids. For example, in air, dielectric breakdown can create a spark or lightning. Understanding dielectric breakdown is crucial in designing electrical systems to prevent failures and ensure safety in various applications, such as capacitors and transmission lines.