For a short period following are interruption, reignition can be produced by a continuous energy process. The paper develops the theory of measurements of are resistance, power loss and reignition voltage during this thermal reignition period of recovery. Experiments are described in which these measurements are made during the first 100????????s of the free recovery of ares in air burning freely between 4mm diameter carbon electrodes. Direct-current pulses of 150 ms duration and of 10, 20 and 40A are used. The results give variations in resistance, power loss and reignition voltage which in the main can be explained by thermal considerations, although the first few microseconds of recovery are difficult to explain in a like manner. A clear distinction is drawn between power-loss voltage and reignition voltage. Assuming a linear relationship between the internal energy and the electrical conductivity of a thermal gas, a linearized theory of interruption is developed which appears to have advantages over previous interruption theories and shows reasonable agreement with the experimental results.
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