Critical behavior of the electrical transport properties in a tunneling-percolation system

We report the confirmation of the tunneling-percolation model predictions by measurements on carbon black-polymer composites, in which the carbon black is of ``low structure.'' From the measurements we have determined the critical resistance exponent t, and the ratio κ/t, where {κ} is the critical relative resistance-noise exponent. The results found are $t=6.4$ and κ/t=0.5. It is shown that these simultaneous new t and κ/t results are consistent only with the predictions of a tunneling-percolation model. It is argued that previously reported values of t and κ/t in similar systems, which deviate from the theoretical predictions of this model, are due to nonrandom dispersion of the particles in these systems.