Breakdown in sulphur hexafluoride and nitrogen under direct and impulse voltages

Abstract

Applying the present theory to this specimen, we have a total domain-wall area in the demagnetised condition of 6 x 0-07 = 0-42cm, 2 and, assuming as before l-5erg/cm 2 for the wall energy, the total wall energy for the specimen is 0-63 erg. In one complete cycle of magnetisation to saturation, this energy would be released twice, and therefore the hysteresis loss due to the domain walls should be 1 -26erg. It therefore appears that l-26erg is the minimum hysteresis loss per cycle for saturation that could be achieved for this specimen, no matter how well purified and heat-treated it might be.The hysteresis loop actually observed by Williams and Shockley is shown in Fig. 6b, with a coercive force of about 0 012Oe (0-96A/m). From the area of the loop and the volume of the specimen, a simple calculation gives the observed hysteresis loss per cycle as 2 • 6erg, compared with 1 *26erg calculated for the domain-wall loss. These estimates of loss are, however, obviously approximate, since some of the available quantities used in the calculations are given to one significant figure only.