According to electrical standards, which material is not considered an effective ground-fault current path?

The effectiveness of a ground-fault current path is pivotal in ensuring safety in electrical systems. Among the materials listed, earth is not typically considered an effective ground-fault current path. While earth can serve as a grounding medium, the primary function of a ground-fault current path is to provide a low-resistance route for fault currents to return safely to the ground or source, thereby minimizing electrocution risk and equipment damage.

Metal conductors can effectively carry fault currents due to their high conductivity, making them reliable pathways. Wood, being an insulator, does not allow current to flow and would not provide a path for fault currents. Water, while it can conduct electricity, does not serve as a standardized method for grounding in electrical systems because of its inconsistent resistivity and the risk associated with using it in electrical applications.

Therefore, among the options, earth is viewed as less effective in providing a reliable ground-fault current path when compared to metals, whereas wood is non-conductive and does not facilitate any current flow at all.