Sections and branches

At the meeting of the Branch held on April 22, Mr. G. E. Marsh delivered a lecture on the “Pinch Interrupter”, a name used to designate the so-called electrolytic type of interrupter by reason of the phenomenon on which the apparatus operates. The general nature of the pinch phenomenon, which may be defined as the contraction in the cross-sectional area of a liquid conductor when the current passing through it is sufficiently large, was described in detail. The mathematical relations connecting the various factors and several equations were shown by means of their graphs, which indicated the involved relationships. The active pressure directed along the axis of a liquid conductor in consequence of this pinch effect was exhibited by means of a modified interrupter. The latter part of the paper dealt with the constructional features of the apparatus. The dependency of the frequency on the size of aperture, and the current density and inductance of the circuit were pointed out, as well as the high capacity effect displayed by the apparatus when operating under certain conditions. The interrupter was of a construction that involved several new and marked features which contribute to its successful operation over long periods. The lecture was followed by a general discussion.