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In this paper, a lightning return-stroke model proposed by the authors is used for investigating the effect of a nonlinear (current-dependent) channel resistance on lightning-induced voltages on an overhead wire. Lightning-induced voltages are shown to behave at early times as if they were calculated by assuming a lossy channel and at later times as if they were calculated by assuming a lossless channel, the transition between early and latter stages being smoothed by the continuous time decay of the channel resistance. Despite such a transitional behavior, it is argued that similar induced-voltage waveforms can be obtained if a channel resistance with constant value between the upper and lower limits associated to the leader and return-stroke channels is suitably selected. It is also shown that in the cases evaluated in this paper simple engineering return-stroke models are able to lead to lightning-induced voltages in relatively good agreement with those predicted by the considered nonlinear return-stroke model. Finally, lightning-induced voltages calculated using the nonlinear return-stroke model are shown to be in good agreement with experimental data.