Explain the phenomenon of breakdown in dielectric materials.
Breakdown in dielectric materials: This electric strength at breakdown is explained as the minimum electric stress generally expressed in kV/cm that cause rupture or breakdown of that material under particular conditions of temperature, waveform, duration, frequency and kinds of electrodes. The electric strength of a material based upon its composition, temperature, thickness and moisture content and to several extents on the time of application of applied voltage. Waveform and steepness of the shape of wave front of the applied voltage also influence this. There is no definite association among these variables, but generally for sheet materials, this electric strength is an inverse function of the thickness and time and reduces with increasing temperature and moisture content. But at breakdown the high electric stress is supposed to cause an inter-atomic displacement of the orbital electrons that alters the atomic structure causing heating and a conducting path in the material. These breakdown mechanisms of gaseous, liquid and solid dielectrics are dissimilar in nature.