Considering that the electrical conductivity of a thermally equilibrium MHD plasma is a strong non-linear function of the gas temperature, the authors first pointed out that the statistically averaged conductivity <σ> should be evaluated by the mean temprature as <σ>=(1+
G)σ(<
T>), where
G is given by the third order Taylor expansion with respect to the temperature fluctuation
T-<
T> and is always positive. Next, in order to obtain a statistically averaged Ohm's law for a turbulent plasma, the correlation <σ′
E′> between the conductivity and the electric field fluctuations has been numerically investigated for a plasma with a 1/7th-power average temperature distribution and layered one-dimensional fluctuation between parallel electrodes. It was shown that the correlation is always negative and the averaged current density as well as the plasma resistance is to be corrected appreciably from the values based on the mean temperature. Finally, it was shown that the correction factor <σ′
E′>/<σ><
E> can be evaluated approximately by a 4th-order polynominal of the relative rms temperature fluctuation √<
T′
2>/<
T> and the relationship is practically insensitive to the variation of the electrode temperature, the boundary-layer thickness and also to the spatial distribution of the fluctuation amplitudes.
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