Electric field strength of the arcs burning through plastic tubes (PE, PP, PMMA, POM, PA, ABS, PVC, PTFE) at atmospheric pressure are measured as a function of arc current (2-500A) for various tube inner diameters (2, 4, and 6mmφ). Tube lengths are 10-30mm. The result shows that, as the curent increases, the electric field strenght decreases in lower current range and increases in higher current range. In lower current range, the electric field strength depends on the material: the electric field strength of PTFE arc is the lowest, that of PVC arc is higher than that of PTFE arc and those of the other material arcs are higher than that of PVC arc. In higher current range, as the current increases, the difference becomes small.
The gas volume ablated from the tube wall by the arc is measured for various tube materials and the arc currents. The result shows that the relationship between the ablation gas volume and the electric field strength in lower current range is linear if the current is constant, whereas that in higher current range is linear regardless of the tube material or the arc current.