Contact resistance in percolating networks

In a large number of experiments it is observed that the electrical conductivity of percolating networks increases with filling, p, as (p-p(c))(2), where p(c) is the percolation threshold over a very broad range of p values. Our Monte Carlo simulations, however, suggest that this power law will only be valid for p<2p(c), with a crossover to a scaling exponent of 1 for higher p values. To resolve this discrepancy we postulate that the experiments are dominated by contact resistance, and in this case we show that the percolation threshold-scaling exponent of 2 holds over an entire range of p values due to the accidental merger of two different scaling laws.