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A theoretical model for the unit cross section of a 1-atm unbounded arc was used to investigate arc behavior. The electrical source was taken as a dc voltage and resistance in series. Because the simulated arc is not radially bounded, the arc V-I characteristic is found to be time varying and dependent on the source values. The results of exercising the model also show that the central temperature of the arc is maintained in the neighborhood of 7000 K and that changes in the source values can only raise this temperature for times on the order of 100 Â¿s, approximately the time for diffusion of a temperature perturbation from the core of the arc to its periphery. The growth of the arc into ambient air is governed by the diffusivity of the ambient air, and is considerably slower.