Which of the following contributes to electrical leakage when a tool is wet?

Water on the grounding conductor is a factor that can significantly contribute to electrical leakage when a tool is wet. When the grounding conductor is wet, it reduces the effectiveness of the grounding system, which is designed to safely conduct electrical fault currents to the ground. This situation increases the risk of electric shock, as moisture creates a path that can allow electrical current to flow where it shouldn’t, potentially through a person who comes in contact with the tool.

Moisture on the casing, while it can impact electrical safety, does not directly relate to the grounding system’s effectiveness. Dirt on the connectors can cause connection issues but is not primarily responsible for leakage in wet conditions. Circuit insulation failure occurs due to faults in the insulating materials of the tool itself, rather than the impact of external moisture on the grounding conductor. Thus, the presence of water on the grounding conductor is the most critical contributor to electrical leakage in this context.