High Pressure Arcs in Common Gases in Free Convection

An oscillographic method is described for measuring the electric gradient $E$ (volts ${\mathrm{cm}}^{-1\mathrm{}}$), current density $I$ (amp. ${\mathrm{cm}}^{-2\mathrm{}}$), total voltage $e$ (volts) as a function of current $i$ in the discharge. The method is applied to arcs in the 0-10-ampere range under conditions of free convection in ${\mathrm{N}}_2$, A, and He in the 1-50-atmosphere pressure range, and to air, C${\mathrm{O}}_2$, and steam at atmospheric pressure. The exponent $n$ and $B$ in $E={\mathrm{Bi}}^{-n}$ are determined for these cases. The range of $n$ is $0.54<n<\mathrm{}0.73\mathrm{}$, and some dependence on pressure is observed. The exponent $m$ in $E=B_0{p}^m$ is measured for ${\mathrm{N}}_2$, ${\mathrm{H}}_2$, He, and A, and is found to be 0.31, 0.32, 0.20, and 0.16, respectively, with some dependence on current. The method is applied to arcs between electrodes of a number of common metals in air.