Ionisation gradient of low resistivity soils and liquids

The effects of moisture contents in sand (from 1% to 10%), grain size (medium and fine), impulse polarity and Earth electrode´s dimension (hemispherical and parallel-plate test cell) on the threshold electric field, E_c value, have been presented in a previous work (N. Mohamad Nor et al., 2005). In that study (N. Mohamad Nor et al., 2005), the E_c value is obtained when two current peaks were observed. However, no E_c value is obtained for low resistivity test media (resistive liquid medium, sand with large percentage of water content=15%, salt with different percentage of water content, and sand-salt soil mixtures (N. Mohamad Nor et al., 2005, 2001), since there was no second current peak was obtained in those test media. This paper is therefore to obtain the E_c value for these low resistivity test media. Using the available voltage and current traces from previous study (N. Mohamad Nor et al., 2001), for the first time the E_c is taken when v-i curve starts to form a loop. It was found that the E_c of low resistivity test media are within the range of E_c suggested in previous studies, which are from 1.3 kV/cm to 20 kV/cm