Investigation into dynamic process of space charge in liquid dielectrics using the Kerr-effect technique

A new dynamic process of space charge in nitrobenzene was observed during measurement of electric field distribution under high DC electric fields by the Kerr electro-optic effect technique. A pair of parallel plate electrodes, in which one was made of red copper (Cu) and another of aluminum (Al), was used. A DC electrical field of 16 kV/m was applied to the sample. When the voltage polarities of electrodes were reversed from Cu(+)-Al(-) to Cu(-)-Al(+), a dynamic process which changed the polarity of space charge in the sample from negative to positive, then back to negative again, was measured. The amplitude of the electric field before the reversal was almost equal to that after the reversal. The polarities of the electrodes had a direct effect on the time of the dynamic process. This showed that the observed dynamic process was caused by space charge in the sample and it had an intimate relationship with the electrode materials and polarities