Abstract <p>Extended (up to several tens of centimeters) high-current (hundreds of amperes) electric arcs in various gases at the atmospheric pressure are studied experimentally and theoretically. Such discharges have been studied on the electric discharge stand of the P-2000 facility of the Institute of Mechanics of Moscow State University. The data on the influence of an external magnetic field on the stability of such discharges and the formation of branched current channels are clarified. One of the areas of the research is the study of the effect of the orientation of the magnetic field imposed on the arc on the processes of development of the discharge in various gas media, such as air, CO₂, Ar, and N₂. The data for argon and nitrogen are presented most fully. The experiments were carried out in a&#xa0;chamber with transparent walls. The calculation and the theoretical study are carried out on the basis of an electrical engineering model using the empirical data on the volt-ampere characteristics of arcs between graphite electrodes. It is found that the stability of high-current arcs is significantly affected by electrode jet-flame dynamics. At the same time, the traditional models of arcs in the external magnetic field without taking these factors into account show that the direction of the external axial field does not affect the stability of the arcs, affecting only the direction of their twisting during the development of helical instability.</p>