The authors have been investigating the electric field-induced motion in mineral oil between plane parallel electrodes after change of electrode polarity. In this paper, the influences of electrode spacing on the motion are reported. Experiments were carried out under two conditions. The first condition was able to accumulate in the vicinity of electrodes all of the charge carriers existing in the oil between electrodes. The second condition was able to accumulate the quantity of charge carriers limited to the magnitude of charging voltage. We used the oils of electric conductivity 4.0×10^-14S/m and 8.9×10^-13S/m and observed time dependence of current and schlieren images of the motion for a range of elerctrode spacing extending from 2.5mm to 025mm at ±0.2MV/m.
The results are as follows: (1) In the cace of the first condition, time when current starts to increase and time for peak current shorten With the increase of the electrode spacing. (2) ln the case of the second condition, these times hecome long with the increase of the electrode spacing. (3) The motion produces a peaked behaviour in the current waveform without distinction of the accumulative condition of charge carriers. (4) The experimental results are well explained by established model.