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The influence of an axial magnetic field on the electron temperature of a vacuum arc plasma was studied experimentally and theoretically for moderate discharge currents of 400-600 A, magnetic flux densities of 0-50 mT, and various cathode materials such as uranium, titanium, and carbon. Experiments were performed using the vacuum arc ion source (VARIS) and the electron energy spectra were measured with a 127° electrostatic cylinder spectrometer. The electron temperature in the inter-electrode gap of a vacuum arc was calculated from an energy balance equation that was supplemented by an magnetohydrodynamic approach of the plasma flow. The plasma flow is constricted by an external axial magnetic field instead of the free spherical plasma flow in its absence, leading to an increase in the electron temperature. The influence of different input parameters such as the magnetic flux density, arc current, the ion to arc current ratio, the initial plasma jet radius, and the distance from the cathode on the electron temperature was studied and compared with the experimental results.